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Thermoplastic polyamide elastomer (TPAE)/calcium silicate (CaSiO3) open‐cell foam with low shrinkage and high expansion ratio was prepared by using supercritical CO2 as a blowing agent. Adding CaSiO3 led to increased melt viscoelasticity and reduced crystallinity of TPAE. The primary mechanism of CaSiO3 promoting TPAE foam to form the open‐cell structure was discussed. The interaction between CaSiO3 and TPAE is fragile, making CaSiO3 easy to fall off the cell wall and form the open‐cell structure during foaming process. The increasing CaSiO3 content leads to increased cell density and thinned cell walls, thus increasing the tensile stress on cell wall. On the other hand, the agglomeration of CaSiO3 increases particle size, making it easier to fall off from the adhesion of TPAE matrix. The two aspects work together to improve the open‐cell content of TPAE foam up to 93.28%. The open‐cell structure is conducive to increasing the gas exchange rate and significantly decreasing foam shrinkage ratio. Finally, TPAE foam with a shrinkage ratio of only 2.68% and an expansion ratio of 18.77 times was obtained. In addition, open‐cell structure improves the adsorption performance of TPAE/CaSiO3 foam by 500%. [ABSTRACT FROM AUTHOR]

Self-reinforcing porous mullite ceramics have attracted considerable attention in the field of insulation and sound absorption materials, due to their precise and controllable porous structure, high temperature and corrosion resistance, and low thermal conductivity. However, the high cost and relatively low performance obstruct their practical applications. In this work, self-reinforcing porous mullite ceramics were fabricated by utilizing construction waste via foam-gel casting and freeze-drying methods, and the impact of blowing agent dosage and sintering temperatures on the microstructures, sound absorption, and thermal insulation properties were systematically investigated. In addition, the related mechanism was also discussed in detail. The results show that, at a sintering temperature of 1000 °C and blowing agent dosage of 0.10 wt%, the self-reinforcing porous mullite ceramics can be successfully obtained, which exhibited a bulk density as low as 0.24 g/cm³ and porosity more than 90 %. Consequently, at a frequency of 2000 Hz, its absorption coefficient reached about 0.81. Furthermore, its thermal conductivity also decreased to about 0.06266 W/(m·K). This development not only unveils innovative avenues for the cost-effective fabrication of porous ceramics but also significantly broadens their potential applications within high-performance thermal insulation and sound absorption domains. [ABSTRACT FROM AUTHOR]

The dimensional accuracy of injection molded parts plays an increasingly significant role in the plastics processing industry, as is the utilization of recycled raw materials. To obtain the desired dimensions and properties of injection moldings, various material modification methods are used simultaneously. The conducted research aimed to assess the impact of hybrid modification of non-nucleated heterogeneously isotactic polypropylene using recovered phosphogypsum and a chemical blowing agent on the shrinkage value and mechanical properties of injection molded parts. Additionally, changes in dimensions and properties of composites with solid and porous structures that occur within 1000 hours of their removal from the injection mold were determined. The research showed that the filler used acts as a nucleating agent causing an increase in the shrinkage of the parts, up to 10 wt%. Similar changes were observed in the case of tensile strength. The increase in the value of this parameter at the lowest phosphogypsum contents used was most likely the result of changes in the crystalline structure of polypropylene. Changes in the mechanical properties of the molded parts that occurred during conditioning are correlated with shrinkage changes that occur from the moment the molded parts are removed from the injection mold. Young's modulus and tensile strength increased linearly for both solid and porous moldings. However, the rate of stiffness increases as a function of shrinkage changes with the filler content. Nevertheless, the opposite tendency was observed in the case of changes in impact strength, the values of which decreased as a function of shrinkage to the greatest extent in the case of unfilled polypropylene. [ABSTRACT FROM AUTHOR]

This study investigates the cell structure control in 50% thermoplastic polyurethane (TPU) and 50% acrylonitrile butadiene styrene (ABS) blend foam using CO2 as a physical blowing agent, focusing on the effects of variable foaming parameters on the microstructure. Samples measuring 25 × 25 × 1 mm were produced and analyzed for foam structure. The foaming process involved saturating the samples with CO2 gas at pressures of 4, 5.5, and 7 MPa, followed by rapid pressure release and immersion in a hot glycerol bath. The foaming parameters included varied temperatures (80, 90, and 120°C) and times (5–80 s). Scanning electron microscope (SEM) analysis provided data on cell size and density. Results indicated that increasing the saturation pressure enhanced CO2 uptake in the ABS/TPU blend, with the CO2 uptake rate peaking early in the process. Higher foaming temperatures and extended foaming times led to increased cell size, cell density, and expansion ratio. These findings highlight the significant role of process parameters in controlling the cell structure of ABS/TPU blend foams, offering valuable insights into optimizing foam properties for industrial applications. Highlights: Optimization of foam parameters leads to cell structure control in ABS/TPU composite foams for industrial applications.Increasing saturation pressure significantly boosts CO2 uptake in ABS/TPU composite foams.Increasing the foaming temperature and duration leads to larger cell sizes, higher cell density, and greater expansion ratios in ABS/TPU composite foams. [ABSTRACT FROM AUTHOR]

Highly efficient microwave absorbents and multilayer composite structures are crucial methods for enhancing electromagnetic wave (EMW) absorbent performance and broadening the bandwidth of materials. Herein, Ni-Fe/NBR microwave-absorbing composite sheets were prepared for the first time by uniformly dispersing Ni-Fe alloy fiber absorbers into a nitrile butadiene rubber (NBR) matrix using a mechanical mixing method. By varying the content and length of Ni-Fe fibers, thickness of Ni-Fe/NBR and blowing agent content (AC), a series of composites with low reflectivity and different frequency bands were obtained in the 2–18 GHz frequency. As a result, the single-layer NBR sheet with a Ni-Fe fiber content of 15% and fiber length of 3 mm can reach a minimum reflection loss (RLmin) of − 11.92 dB at a thickness of 2.7 mm. Secondly, it is noteworthy that double-layer stacked single-layer NBR absorbers can broaden the absorption bandwidth and improve the absorption effect. Furthermore, varying the positions of the upper and lower layers of sheet materials can yield disparate outcomes. The double-layer Ni-Fe/NBR absorber can achieve an RLmin of − 38.05 dB. Its effective absorption bandwidth (EAB) is 5.06 GHz in the C band and 3.44 GHz in the Ku band. This work provides new ideas for the design of efficient wave-absorbing flexible composites with structural functionalization. [ABSTRACT FROM AUTHOR]

This study investigates the modeling and experimental validation of cell morphology in microcellular-foamed polycaprolactone (PCL) using supercritical carbon dioxide (scCO2) as the blowing agent. The microcellular foaming process (MCP) was conducted using a solid-state batch foaming process, where PCL was saturated with scCO2 at 6 to 9 MPa and 313 K, followed by depressurization at a rate of −0.3 and −1 MPa/s. This study utilized the Sanchez–Lacombe equation of state and the Peng–Robinson–Stryjek–Vera equation of state to model the solubility and density of the PCL-CO2 mixture. Classical nucleation theory was modified and combined with numerical analysis to predict cell density, incorporating factors such as gas absorption kinetics, the role of scCO2 in promoting nucleation, and the impact of depressurization rate and saturation pressure on cell growth. The validity of the model was confirmed by comparing the theoretical predictions with experimental and reference data, with the cell density determined through field-emission scanning electron microscopy analysis of foamed PCL samples. This study proposes a method for predicting cell density that can be applied to various polymers, with the potential for wide-ranging applications in biomaterials and industrial settings. This research also introduces a Python-based numerical analysis tool that allows for easy calculation of solubility and cell density based on the material properties of polymers and penetrant gases, offering a practical solution for optimizing MCP conditions in different contexts. [ABSTRACT FROM AUTHOR]

This document is a collection of patents related to elastomers and plastics, covering a wide range of topics and inventions. The patents include innovations in the production of carbon black, synthesis of block copolymers, preparation of biodegradable latex compositions, creation of polymer composites, development of catalyst systems for polyolefin production, formulation of polyol blends for rigid foams, design of polymer particles with gradient compositions, preparation of polyurethane/polyisocyanurate foam blocks, formulation of rubber compositions, production of polyvinyl alcohol-based resin films, composition of polyethylene for filaments or fibers, development of thermoplastic resin compositions, creation of dielectric elastomeric materials, and formulation of medical rubber compositions. These patents offer valuable insights and innovations in the field of elastomers and plastics, with applications ranging from medical materials to fire-retardant composites. [Extracted from the article]

The processing of long glass fibre-reinforced thermoplastics results in considerable fibre damage, particularly during plasticising. By using thermoplastic foam injection moulding (FIM) with a constant blowing agent atmosphere, fibre damage during plasticisation can be reduced. This can be attributed to the reduction of the melt viscosity on the one hand and the influence of the melting behaviour on the other. Therefore, the influence of the FIM and the process parameters on the fibre length and the fibre length distribution are analysed and compared with the influence of the process parameters on the melt viscosity. [ABSTRACT FROM AUTHOR]

In this work, a new class of fourth-generation, zero ozone depletion potential, hydrofluoroolefin-based blowing agents were used to prepare phenolic foam. While hydrofluoroolefin blowing agents have been used previously to prepare polyurethane foams, few studies have been reported on their use in phenolic foams. We introduce an effective method for foam preparation using two low-boiling blowing agents, cis-1,1,1,4,4,4-hexafluoro-2-butene and trans-1,1,1,4,4,4-hexafluoro-2-butene, and their combinations with hexane. Traditionally, phenolic foams have been prepared using chlorofluorocarbons and hydrochlorofluorocarbons, which can have harmful effects on the environment due to their high ozone depletion potential or global warming potential. Conductor-like screening model for real solvents (COSMO-RS) modeling studies were performed to understand the effects of different blowing agent combinations on their boiling points. A series of phenolic foams were prepared by varying the concentration of the hydrofluoroolefin and the hydrofluoroolefin–hexane blowing agent combinations. The concentrations of the surfactant, Agnique CSO 30, and the toughening agent, polyethylene glycol, were also varied to yield a formulation with the optimal properties. The foams formulated with the hydrofluoroolefin–hexane mixture displayed a higher compressive strength and a lower thermal conductivity than those prepared with either hydrofluoroolefin or hexane alone. The cell microstructure of all the foams was examined using scanning electron microscopy. By introducing flexible chains into the resin matrix, PEG facilitates proper distribution of hydrofluoroolefin–hexane blowing agents and other reagents and thereby increases the mechanical strength of the foam. [ABSTRACT FROM AUTHOR]

The main objective of this study was to utilize coal gangue as the primary raw material and SiC as the foaming agent to successfully prepare foamed ceramics using the high-temperature foaming method. The study investigated the composition and crystal phases of the foamed ceramics formulation, the influence of sintering parameters on the microstructure and physical properties of the samples, as well as the reaction mechanisms during the foaming process. The experimental results showed that when the SiC addition amount was 2.5 wt%, the sintering temperature was 1230°C, and the sintering time was 60 min, the bulk density of the foamed ceramics reached as low as 0.414 g/cm3, with a compressive strength of 1.64 MPa and a closed porosity as high as 74.86%. Additionally, the water absorption and thermal conductivity were simultaneously reduced to 1.48% and 0.1968 W/(m·K), respectively. Besides maximizing the utilization of coal gangue, foamed ceramics also demonstrated excellent porous structure and physical properties, making them suitable for use as thermal insulation materials. [ABSTRACT FROM AUTHOR]

In physical foaming processes of thermoplastics, a liquid mixture consisting of a molten polymer with a dissolved blowing agent is extruded through a die or injected into a mold. The morphology of the foam matrix strongly depends on the mutual diffusion coefficient D11 of the liquid polymer-blowing agent mixture. For a better understanding of the underlying physical mechanisms during the foaming process and the development of corresponding models, accurate knowledge of D11 is needed. This work reports on the simultaneous measurement of D11 and the thermal diffusivity a of liquid mixtures consisting of polystyrene melts with dissolved nitrogen (N2) or carbon dioxide (CO2) at mass fractions wsolute up to 0.003 or 0.02 and temperatures T between (433 and 533) K using dynamic light scattering (DLS). The determined D11 range is between (1 and 4) × 109 m2⋅s−1 and are slightly larger for the mixtures containing N2 at a given T and wsolute. D11 could be determined with an average expanded relative uncertainty of 18%. Considering all investigated state points and the achieved experimental uncertainties, both D11 and a are independent on the amount of dissolved gas, despite relatively large mole fractions of the dissolved blowing agents xsolute of 0.997 and 0.93. [ABSTRACT FROM AUTHOR]

The study examined the feasibility of employing technological lignosulfonates as binders in blowing processes to produce small casting cores for shaped iron castings, analogies to the currently in-use Cold-Box Amin procedure. In the study, it has been demonstrated that lignin materials offer several benefits, including workplace safety, within the foundry itself, and in terms of maintaining environmental hygiene in the vicinity of a similar manufacturing facility. It is indicated that the cost of binders could drop twice when using the suggested lignin components. Mixtures with experimental compositions have been proposed and put to the test. The sand-oligosulfonate mixture's composition has quantitative properties that have been determined. Binders exhibiting stable properties and high strength indicators (up to 3.0 MPa) were developed after processing. The nonionic surfactant class was determined to include the most effective additions. It was experimentally demonstrated that applying specific nonionic surfactant types as technological lignosulfonate modifiers boost and stabilizes properties by a significant order of magnitude (from 0.05 MPa to 0.5-0.7 MPa) %, concerning specific binding ability). Consequently, excellent cast iron castings and a prototype batch of cores were created. A significant emphasis is placed on developing special machinery for lignin binders. [ABSTRACT FROM AUTHOR]

Cryogenics is the science and technology of very low temperatures, typically below 120 K. The most common applications are liquified natural gas carriers, ground-based tanks, and propellant tanks for space launchers. A crucial aspect of cryogenic technology is effective insulation to minimise boil-off from storage tanks and prevent frost build-up. Rigid closed-cell foams are prominent in various applications, including cryogenic insulation, due to their balance between thermal and mechanical properties. Polyurethane (PU) foam is widely used for internal insulation in cryogenic tanks, providing durability under thermal shocks and operational loads. External insulation, used in liquified natural gas carriers and ground-based tanks, generally demands less compressive strength and can utilise lower-density foams. The evolution of cryogenic insulation materials has seen the incorporation of environmentally friendly blowing agents and bio-based polyols to enhance sustainability. Fourth-generation physical blowing agents, such as HFO-1233zd(E) and HFO-1336mzz(Z), offer low global warming potential and improved thermal conductivity. Additionally, bio-based polyols from renewable resources like different natural oils and recycled polyethylene terephthalate (PET) are being integrated into rigid PU foams, showing promising properties for cryogenic applications. Research continues to optimise these materials for better mechanical performance and environmental impact. [ABSTRACT FROM AUTHOR]

In this study, a sustainable biocomposite foamed recycled high-density polyethylene (rPE) with agave fiber at different compositions (0, 10, 20, and 30 wt%) with and without compatibilizer and a blowing agent were prepared using a twin-screw extruder, demonstrating an innovative use of waste materials. Samples for static and dynamic mechanical analysis (DMA) tests were prepared by injection molding. Additionally, characterization by capillary rheology, Fourier transform infrared spectroscopy (FTIR), and morphological studies was performed. For the prepared composites, the viscosity increases, while the melt flow index decreases with fiber content. Tensile and flexural properties increase with fiber content. For the composite with 30 wt% of fiber, the tensile modulus and the flexural modulus increased by 54% compared with pure recycled HDPE, while the tensile and flexural strength for this composition increased by 8.7% and 33%, respectively. The same trends are obtained by means of the DMA study, where the storage modulus of the modified composite with 30 wt% of agave fiber increased 70% compared with that of recycled HDPE at 20 °C. The improvements in properties obtained with agave fiber and the compatibilizer, show tangible recovery ways for foamed recycled HDPE. This work not only addresses the critical need for sustainable material options, but also contributes to the circular economy by valorizing agricultural and post-consumer waste. The potential applications of this biocomposite are broad, including lightweight building materials and automotive components, where sustainability and material performance are increasingly a priority. [ABSTRACT FROM AUTHOR]

The preparation of rigid polyurethane foam with uniform pore size is extremely challenging. In this work, double‐effect baking powder was used as foaming agent, and rigid polyurethane foam with regular morphology was successfully prepared through semi‐prepolymerization. The rigid polyurethane foam apertures with regular morphology were controlled by the secondary release of CO2 when the content of baking powder is 0.30 part. Combined with theoretical calculation and experimental test, it is found that the particle size distribution, wall thickness, and hole shape are uniform, regular, thin, polygonal, and few broken holes. The compression strength, contact angle, and surface energy of the rigid polyurethane foam are 33.36 kPa, 109.6°, and 21.8 mJ/m2 after adding 0.20 part of double‐effect baking powder, respectively. By adjusting the amount of double‐acting baking powder, the porosity, mechanical properties and foam rate of the polyurethane foams could be significantly improved. Due to the molecular solvation effect, rigid polyurethane foams will deform in the water and oil due phase, but it can remain stable for a long time at room temperature without solvent. It provides a new method for the preparation of rigid polyurethane foam, which is expected to be widely used in transportation and other fields. Highlights: Baking powder was firstly used as a foaming modifier for rigid polyurethane.Baking powder releases CO2 twice to ensure uniform structure of polyurethane cell.Rigid polyurethane foam has long‐term stability and regular, uniform cell holes.The porosity and mechanical properties of foams could be significantly improved.Foaming mechanism of rigid polyurethane using baking powder was firstly revealed. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) foams are widely used for the advantages of light weight and reducing energy consumption. So, the preparation of environmental friendly and efficient blowing agent is essential. The use of supercritical carbon dioxide (CO2) as physical blowing agent requires harsh experimental conditions such as high‐pressure and temperature. In this study, CO2 was captured by 1, 2‐cyclohexanediamine (TRK) under atmospheric pressure, and reversibly released under heating as a blowing agent with nanosponges (NS) used as the carrier (NS:TRK‐CO2). Furthermore, three ethoxy silane coupling agents were selected to improve the compatibility between heterogeneous nucleating agent (cyclodextrin nanosponges, NS) and PE, so as to improve the nucleation effect of NS and the comprehensive properties of PE composites. Analyses showed that triethoxyvinyl silane (VTES) was a suitable candidate for improving the compatibility of NS and PE. The addition of NS:TRK‐CO2@VTES not only improved the crystallization performance, but also improved the complex viscosity and storage modulus, and enhanced the thermal properties of PE composites. The optimal cell morphology was obtained by introduction of NS:TRK‐CO2@VTES with 5 wt%, the minimum cell diameter was 50 μm, and the maximum cell density was 9.4 × 104 cells/cm3. Compared with the other PE composites, PE/NS:TRK‐CO2@VTES composites showed excellent mechanical, thermal, and sound insulation properties. The maximum impact strength was 7.62 KJ/m2, which was two times higher than pure PE. The thermal conductivity was 0.054 W/m k, the sound absorption coefficient was 0.836 at 1500 Hz. [ABSTRACT FROM AUTHOR]

Geopolymer foam concrete (GFC), an emerging thermal insulation material known for its environmentally friendly and low-carbon attributes, has gained prominence for its use in bolstering building energy efficiency. A critical challenge in GFC production is foam destabilization by the alkaline environment in which foam is supersaturated with salt. In this study, GFC was prepared by using triterpene saponin (TS), sodium dodecyl sulphate (SDS), and cetyltrimethylammonium bromide (CTAB) as blowing agents, with fly ash as the precursor and calcium carbide slag (CA) combined with Glauber's salt (GS, Na2SO4 ≥ 99%) as the activator. The effect of GFC on mechanical properties was analyzed by examining its fluidity, pore structure, dry density, and compressive strength. The results show that TS has a stable liquid film capable of adapting to the adverse effects of salt supersaturation and alkaline environments. TS is highly stable in the GFC matrix, and so the corresponding pore size is small, and the connectivity is low in the hardened GFC. In addition, the hydration products of GFC exhibit different morphologies depending on the surfactant used. TS has better water retention due to hydrogen bonding, which facilitates the hydration process. [ABSTRACT FROM AUTHOR]

Anisotropy in naturally occurring or synthetic microcellular structures is an important feature for the development of materials with high specific stiffness and strength, in addition to creating materials with unique physical properties. Polymeric foams constitute a broad class of materials that are widely used for their advantages of low density, high specific mechanical properties and high insulative properties. Traditional synthetic routes are slow, energy demanding processes that employ the use of high temperature ovens, freezers, or high‐pressure equipment. Herein we present a convenient and energy efficient method to produce anisotropic high performance polymeric foams via rapid radically induced cationic frontal polymerization coupled with chemical blowing agents. The degree of pore orientation and degree of anisotropy are a result of the propagating front working in concert with the foam volume expansion. This paper presents results into FP foam formation to illustrate how changes in boundary conditions and front initiation position affect both the microcellular structure and their resulting physical and mechanical properties. Additionally, results are presented to show how changes in resin formulation, such as the addition of nanoparticles affect both properties as well as the microcellular structure and anisotropy. [ABSTRACT FROM AUTHOR]

This study employs machine learning algorithms to analyze the bead foam extrusion process and to assess the impact of processing parameters, specifically focusing on their effects on bead foam density and melt pressure in under water granulation (UWG) for polylactic acid (PLA). These interrelated parameters, influenced by processing parameters such as temperature, screw speed, and blowing agent, possess challenges for traditional empirical methods to capture. The key factors that significantly impact the prediction of melt pressure in UWG are blowing agent, injector pressure, temperature in B‐extruder and die size. Likewise, essential parameters for predicting bead foam density comprise blowing agent, injector pressure, temperature in B‐extruder, die plate temperature, melt temperature in B‐extruder, and melt pressure in B‐extruder. Machine learning (ML) models were employed to forecast bead foam density and melt pressure in UWG using various processing parameters in PLA bead foam extrusion. The random forest model achieved a high coefficient of determination R2 score of 0.96 for predicting melt pressure in UWG. Additionally, the decision tree model demonstrated effective predictions for bead density, with the R2 score: 0.81. These ML models can be applied to diverse materials, leading to more sustainable, efficient processes for bead foam extrusion. [ABSTRACT FROM AUTHOR]

Porous conductive polymer structures, in particular Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) structures, are gaining in importance due to their versatile fields of application as sensors, hydrogels, or supercapacitors, to name just a few. Moreover, (porous) conducting polymers have become of interest for wearable and smart textile applications due to their biocompatibility, which enables applications with direct skin contact. Therefore, there is a huge need to investigate distinct, straightforward, and textile-compatible production methods for the fabrication of porous PEDOT:PSS structures. Here, we present novel and uncomplicated approaches to producing diverse porous PEDOT:PSS structures and characterize them thoroughly in terms of porosity, electrical resistance, and their overall appearance. Production methods comprise the incorporation of micro cellulose, the usage of a blowing agent, creating a sponge-like structure, and spraying onto a porous base substrate. This results in the fabrication of various porous structures, ranging from thin and slightly porous to thick and highly porous. Depending on the application, these structures can be modified and integrated into electronic components or wearables to serve as porous electrodes, sensors, or other functional devices. [ABSTRACT FROM AUTHOR]

The soft PBAT foam shows good flexibility, high elasticity, degradable nature, and it can be used as an environmental-friendly candidate for EVA and PU foams. Unfortunately, there are few reports on the application of PBAT as a soft foam. In this study, PBAT foam was fabricated by a pressure quenching method using CO2 as the blowing agent. A significant volume shrinkage of about 81% occurred, where the initial PBAT foam had an extremely high expansion ratio, of about 31 times. A 5–10 wt% PBS with high crystallinity was blended, and N2 with low gas solubility and diffusivity was mixed, with the aim of resisting foam shrinkage and preparing PBAT with a high final expansion ratio of 14.7 times. The possible mechanism behind this phenomenon was established, and the increased matrix modulus and decreased pressure difference within and outside the cell structure were the main reasons for the shrinkage resistance. The properties of PBAT and PBAT/PBS foams with a density of 0.1 g/cm3 were measured, based on the requirements for shoe applications. The 5–10 wt% PBS loading presented advantages in reducing thermal shrinkage at 75 °C/40 min, without compromising the hardness, elasticity, and the compression set, which ensures that PBAT/PBS foams have good prospects for use as soft foams. [ABSTRACT FROM AUTHOR]

Ethylene–vinyl acetate copolymer (EVA), a crucial elastomeric resin, finds extensive application in the footwear industry. Conventional chemical foaming agents, including azodicarbonamide and 4,4′-oxybis(benzenesulfonyl hydrazide), have been identified as environmentally problematic. Hence, this study explores the potential of physical foaming of EVA using supercritical nitrogen as a sustainable alternative, garnering considerable interest in both academia and industry. The EVA formulations and processing parameters were optimized and EVA foams with densities between 0.15 and 0.25 g/cm3 were produced. Key findings demonstrate that physical foaming not only reduces environmental impact but also enhances product quality by a uniform cell structure with small cell size (50–100 μm), a wide foaming temperature window (120–180 °C), and lower energy consumption. The research further elucidates the mechanisms of cell nucleation and growth within the crosslinked EVA network, highlighting the critical role of blowing agent dispersion and localized crosslinking around nucleated cells in defining the foam's cellular morphology. These findings offer valuable insights for producing EVA foams with a more controllable cellular structure, utilizing physical foaming techniques. [ABSTRACT FROM AUTHOR]

Since reservoirs with permeability less than 10 mD are characterized by high injection difficulty, high-pressure drop loss, and low pore throat mobilization during the water drive process, CO2 is often used for development in actual production to reduce the injection difficulty and carbon emission simultaneously. However, microfractures are usually developed in low-permeability reservoirs, which further reduces the injection difficulty of the driving medium. At the same time, this makes the injected gas flow very fast, while the gas utilization rate is low, resulting in a low degree of recovery. This paper conducted a series of studies on the displacement effect of CO2-soluble foaming systems in low-permeability fractured reservoirs (the permeability of the core matrix is about 0.25 mD). For the two CO2-soluble blowing agents CG-1 and CG-2, the effects of the CO2 phase state, water content, and oil content on static foaming performance were first investigated; then, a more effective blowing agent was preferred for the replacement experiments according to the foaming results; and finally, the effects of the blowing agents on sealing and improving the recovery degree of a fully open fractured core were investigated at different injection rates and concentrations, and the injection parameters were optimized. The results show that CG-1 still has good foaming performance under low water volume and various oil contents and can be used in subsequent fractured core replacement experiments. After selecting the injection rate and concentration, the blowing agent can be used in subsequent fractured cores under injection conditions of 0.6 mL/min and 2.80%. In injection conditions, the foaming agent can achieve an 83.7% blocking rate and improve the extraction degree by 12.02%. The research content of this paper can provide data support for the application effect of a CO2-soluble blowing agent in a fractured core. [ABSTRACT FROM AUTHOR]

Blowing agent-assisted extrusion cooking is a novel processing technique that can alter the expansion of extruded snacks and, thus, enhance their physical appeal, such as texture. However, to this day, this technique has only been studied for ingredients with limited protein contents (<30%). In this study, protein-enriched snacks were extruded using nitrogen gas as a blowing agent at a wide protein range (0–50%) to better explore the potential of this technique in manufacturing high-protein snacks. The results showed that, with nitrogen gas injection, extrudate radial expansion was significantly (p < 0.05) improved at 10% and 40% protein, while extrudate density was significantly reduced at 30% and 50% protein. Nitrogen gas-injected extrudates, especially at 50% protein, exhibited improvements in texture, including a reduction in hardness and an increase in crispness. Collectively, this study showed the promising potential of nitrogen gas-assisted extrusion in improving the physical appeal of innovative healthy snacks at a high protein level (i.e., 50%). [ABSTRACT FROM AUTHOR]

Polyurethane (PU) foams are key players within the large foam market, with applications such as thermal insulating materials, cushioning, protective equipment, etc. With the current regulatory constraints on the use of toxic isocyanates and the ambitious goals to increase the renewable content of plastics while valorizing waste, isocyanate-free liquid formulations containing biofillers that are able to easily self-foam are needed for more sustainable PU foams in the future. Herein, we incorporate various abundant waste stream-sourced biofillers (proteins, lignin derivatives, and polysaccharides) into isocyanate-free PU formulations composed of CO2-based poly(cyclic carbonate)s, diamines and a catalyst. The formulations containing up to 30 wt% of biofillers are foamed at 100 °C without adding any external foaming agent. Moisture naturally present in the biofillers partially hydrolyses the cyclic carbonates, which generates the blowing agent (CO2). The biofiller, even at a low content (1 wt%), stabilizes the growing cells, providing homogeneous foams. Although the nature of the biofiller does not significantly affect the foams' density and morphology, their mechanical properties are strongly affected, for example from a rigid foam with 10 wt% keratin (compression modulus (E) = 21.9 MPa) to a flexible one with chitosan (E = 0.2 MPa). Preliminary studies indicate that the biofiller does not prevent the foam recycling into polymer films by hot pressing. Virtually any kind of moisture-containing biowaste can be used as a water reservoir to foam the formulations while increasing the bio-based content of the material, which reaches 97% when selecting bio-based monomers. This process valorizes abundant waste stream-sourced biofillers for producing more sustainable PU foams. [ABSTRACT FROM AUTHOR]

Liquid crystal polymers (LCP) and polytetrafluoroethylene (PTFE) were in situ fibrillated to produce polyethylene terephthalate (PET)/LCP/PTFE composites using a simple and scalable extrusion drawing techniques. The PET/LCP/PTFE composites included high-aspect-ratio PTFE fibrils and rod-like LCP fibrils. The simultaneous in situ fibrillation of LCP and PTFE exerted synergistic effects on crystalline behaviour and viscosity of PET, especially for mechanical properties of PET and its foam. The tensile strength of PET/LCP/PTFE composites and impact strength representing improvements of 34% and 62% over those of PET. The improved mechanical properties can be attributed to the simultaneous abundance of orienting rod-like rigid LCP fibrils and tangling flexible PTFE fibrils in the PET matrix, which contributed to stress transfer from matrix to fibrils. A simultaneously in situ fibrillated PET/LCP/PTFE composite foam was fabricated using a batch foaming system with supercritical CO2 as blowing agent. The cell diameter of this foam decreased by 23% over that of standard PET foam, while its cell density increased twofold. The smaller cell diameter of PET/LCP/PTFE foam and superior mechanical properties of PET matrix collectively led to the good mechanical properties of PET/LCP/PTFE foam. Specifically, the compressive strength of the PET/LCP/PTFE foam represents a 35% increase over that of PET foam. [ABSTRACT FROM AUTHOR]

Poly(propylene carbonate-co-phthalate) (PPC-P) is an amorphous copolymer of aliphatic polycarbonate and aromatic polyester; it possesses good biodegradability, superior mechanical performances, high thermal properties, and excellent affinity with CO2. Hence, we fabricate PPC-P foams in an autoclave by using subcritical CO2 as a physical blowing agent. Both saturation pressure and foaming temperature affect the foaming behaviors of PPC-P, including CO2 adsorption and desorption performance, foaming ratio, cell size, porosity, cell density, and nucleation density, which are investigated in this research. Moreover, the low-cost PPC-P/nano-CaCO3 and PPC-P/starch composites are prepared and foamed using the same procedure. The obtained PPC-P-based foams show ultra-high expansion ratio and refined microcellular structures simultaneously. Besides, nano-CaCO3 can effectively improve PPC-P's rheological properties and foamability. In addition, the introduction of starch into PPC-P can lead to a large number of open cells. Beyond all doubt, this work can certainly provide both a kind of new biodegradable PPC-P-based foam materials and an economic methodology to make biodegradable plastic foams. These foams are potentially applicable in the packaging, transportation, and food industry. [ABSTRACT FROM AUTHOR]

Aluminum foams have emerged as a remarkable engineering material, exhibiting exceptional structural performance and many excellent properties. This has led to a rise in their application in various fields. The investigation and development of aluminum foam have led to the discovery of multiple applications in numerous industries, including the aerospace, automotive, petrochemical, and building materials industries. Foam made of aluminum, one of the most well-known examples of metallic foams, is a significant technological advancement in the foams industry. This article aims to comprehensively analyze the manufacturing techniques that employ blowing agents, such as alumina, titanium hydride, and sodium chloride. This article explores the unique properties and diverse applications of aluminum foams. In addition, the current status of research and development in aluminum foam is discussed. It accomplishes this by providing an overview of existing developments and identifying future opportunities in this industry. This review article is an invaluable resource for academics and industry professionals interested in aluminum foams, as it provides valuable insights into production procedures, properties, applications, and ongoing research. [ABSTRACT FROM AUTHOR]

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The swelling step of polymer particles or beads with blowing agents and monomers is one of the factors that directly affect the performance properties of expandable core–shell particles, including morphology, composition, and expansion degree. In this regard, the present work investigated the effect of swelling agents on polypropylene (PP) beads. Swelling agents were used to perform swelling tests in both bulk and suspension media at different temperatures and stirring rates. Additionally, a mass transfer model was implemented to predict the swelling degree at the analyzed experimental conditions. The obtained results indicated the important effect of temperature on swelling in both bulk and suspension tests. Among the investigated swelling agents, higher rates of PP beads swelling were observed when styrene was employed (~80 wt%), when compared to methyl methacrylate (~20 wt%), vinyl acetate (~9 wt%), and acrylonitrile (~6 wt%). Moreover, it seems that the stirring rate does not exert a considerable influence on the swelling rates, indicating that swelling is controlled by thermodynamic constraints and particle properties. Finally, experimental results showed that the final saturation concentration of the swelling agent can be reached before 1 hour of swelling, indicating that the swelling kinetics can be much faster than the polymerization kinetics. Highlights: The effects of non‐conventional swelling agents on PP were investigated.The swelling presented a fast dynamic behavior.The swelling dynamics was controlled by the solubility of the swelling agent.The highest swelling degree was obtained with styrene. [ABSTRACT FROM AUTHOR]

Previous studies on epoxy foams were subjected to the specific property, and improvements in thermal insulation or dielectric property were usually accompanied by the sacrifice of mechanical strength or thermal stability. The current research reported a high‐performance epoxy foam by the pre‐curing process using E‐51/DDS and expandable microsphere (EMP) as polymer matrix and physical blowing agent, respectively. The effect of EMP loading on the structure & property of epoxy foam was reported. The mean diameter of E‐51/EMP foam was in the range of 19–21 μm. The compression property of E‐51/EMP foam was fit for the power‐law model and its integrity was well maintained during compressive test. Compared with bulky epoxy, a significant decrease of thermal conductivity of 62.93% was observed in 10 wt% EMP‐filled epoxy foam. E‐51/EMP foam showed superior thermal stabilities, with a T5% of over 300°C. The dielectric constant was decreased by 54.5% from 4.92 in bulky epoxy to 2.24 in E‐51/EMP foam (10 wt% EMP). Notably, there was a percolation phenomenon of EMP (6 wt%) regarding on the structure & property of E‐51/EMP foam. This study provides lightweight, robust, high‐temperature‐resistant, and low‐dielectric‐constant epoxy foams with the wide application prospects in buoyant, electronic packaging, and energy‐saving industries. [ABSTRACT FROM AUTHOR]

In conventional foams, anisotropy within the microcellular structure can only be achieved through confinement in one or more directions during the foaming process. Herein, we present a novel, versatile, and energy efficient method to create unique high‐performance foams where the anisotropy of the microcellular and the microcellular structure itself is not dictated by external confinement during the foaming process. To generate such foams, an initial crosslinked gel is first created where the crosslink density of the gel can be tuned by UV intensity and cure time. Next, the gel can be foamed while simultaneously creating a second network via radically induced cationic frontal polymerization (RICFP). In this case, the anisotropy in the foam is dictated by propagation front during the RICFP and the microcellular morphology and cell surface area are dictated by the crosslink density of the gel. These two unique qualities lead to rigid foams that can be generated from a gel without the need for confinement where the microcellular size and shape can be tuned by the crosslink density of the gel precursor. A one‐pot liquid system composed of miscible epoxies, acrylates, and chemical blowing agents (CBAs), allows for control over the foam physical, mechanical, and thermal properties with glass transition temperatures ranging from 74.7 to 125.8°C. Additionally, by patterning the crosslink density of the initial gel through controlled exposure of UV, complex microcellular structures can be formed that are not possible in conventional foaming processes. This positions gel frontal polymerization and foaming as an advanced technique to produce high performing anisotropic foams with a wide array of tunable physical, mechanical, and thermal properties. [ABSTRACT FROM AUTHOR]

In this study, we prepared nanosponges (NS) by crosslinking the hydroxyl group of β-cyclodextrin (CD) molecular. Furthermore, we modified the CD molecular by 1, 2-cyclohexanediamine (TRK) through simple chemical method. CD, NS and CD-TRK were used as nucleating agent in the injection foaming process of polyethylene (PE) with 4, 4'-oxydibenzenesulfonyl hydrazide as blowing agent. With addition of CD-TRK, the crystallinity increased from 39.17% for pure PE to 46.02% for PE/CD-TRK-1.0 composites. Results showed that PE/CD-TRK-1.0 composites presented the best foam morphology. The cell density increased by about 10 times, while the cell diameter reduced by about 56% compared with that of pure PE. Scanning electron microscopy analysis showed that CD-TRK exhibited more compact and dense network structure with uniform cavity distribution, which may reduce the cell nucleation barrier and provide proper nucleation site for cells. The dynamic mechanical analysis showed that PE/CD-TRK-1.0 composites displayed proper modulus and viscoelasticity, which were favor for cell nucleation, growth and stabilization, resulting in the best cell morphology of PE/CD-TRK composites. Tensile and impact strength of foaming PE composites were systematically analyzed. The maximum impact strength reached 27.4 KJ·m−2, and the maximum tensile strength reached 27.5 MPa. [ABSTRACT FROM AUTHOR]

Solvent-borne polyurethane (PU) is the main product in PU synthetic leather, which has soft handling, breathability, and moisture permeability properties by wet type. The PU film would produce the irregular foam cell by solvent exchanging water. This traditional process would use a lot of dimethylformamide, and it causes much pollution of the environment. Therefore, the water-borne polyurethane system is essential in the textile industry. This study adopted the patented prepolymer process for solvent-free water-borne polyurethane (SFWPU); the foam was formed by a blowing agent and then, coated on the polyester textile with SFWPU foam by coating machine. This research focuses on the polyol composition equivalent ratio of poly(1,4-butylene adipate) glycol (PBA) and poly(tetramethylene ether) glycol from 30:70, 20:80, 10:90, and 0:100. The crystallinity increased on the foam properties with increasing the PBA composition, affecting the foam and tensile properties. Moreover, this research finds that higher crystallinity polyol of PBA contents increased, modulus of SFWPU is increased, and tensile strength is decreased. The scanning electron microscope finds the foam cell would expand by increasing PBA contents, which affects the textile's air permeability and water vapor transmission. The 10% PBA equivalent of ester–ether type SFWPU foam coated on textile, which has windproof and keeps the moisture permeability. [ABSTRACT FROM AUTHOR]

To solve the problems of brittleness, high cost, and the complicated construction process of traditional filling materials for filling abandoned roadways, various aspects of the physical and mechanical properties of the materials were studied using laboratory tests and were applied in coal mines. The research shows that the self-developed inorganic cementitious filling material has the advantages of being low cost, easy to cut and wash, and having good filling performance. A foaming agent is a direct factor in controlling the volume expansion of inorganic cementitious filling materials; the increase in the volume of slurry foaming with the addition of a foaming agent initially showed a large and then a small trend with a foaming agent dosage of 100 g. The increase in the volume of slurry foaming is the largest at 56.28%. The effect of the B material (calcium stearate+ J85 rapid-setting agent) on the foaming time and the number of foaming times of the slurry was significant. Foam stabilizers in the B material make the slurry particles uniformly distributed inside the slurry, while quick-setting agents control the initial and final setting time by affecting the slurry setting speed. The water/cement ratio directly affects the foaming times of the slurry but has little effect on the foaming time and setting speed. When the water/cement ratio is less than 1:2, the slurry foaming effect is poor, and the foaming volume remains unchanged. The strength of the material is significantly affected by the proportion of B material and the amount of blowing agent, and the compressive strength of materials with different compositions and ratios varies greatly. A whole set of systems of new inorganic gelatinized abandoned roadway filling materials was researched and applied in coal mines, achieving good results. [ABSTRACT FROM AUTHOR]

Unconventional injection methods include i.e. blowing injection that allows for production of moldings with a lower weight while maintaining mechanical properties of detail. Due to the fact that most polymers are dyed at the processing stage, it is important to examine the simultaneous effect of blowing and colorbatch, as well as variable processing conditions, on the functional properties of moldings made of the most popular construction material, i.e. ABS. Samples were made of ABS polymer without and with the addition of a colorbatch containing brown pigment on ABS matrix, and blowing agent. Variable processing conditions were: mold and injection temperature, holding pressure and time. Other parameters were constant. Samples were tested for basic functional properties such as color, gloss, mass, density and thickness. Moldings produced with a higher blowing agent content and a higher injection temperature were characterized by lower mass. No significant influence of processing parameters and content of colorbatch on mass of samples was found. Blowing agent has no significant impact on thickness of moldings, regardless of processing conditions. Addition of a colorbatch influenced samples’ gloss. Increase in colorbatch and blowing agent content and mold temperature allow to obtain moldings with a higher surface gloss. Colorbatch also changed color of samples – a decrease in luminance L even by about 40% and great changes in parameters “a” and slight changes in parameter “b”. It was found that blowing agent content had the greatest influence on density of moldings. Injection temperature and colorbatch, do not significantly affect density of moldings.

Bio‐based or partially bio‐based thermally expandable microspheres (TEMs) were synthesized by suspension (co)polymerization of the bio‐based monomer α‐methylene‐γ‐valerolactone (MeMBL) together with acrylonitrile and/or methyl methacrylate to form expandable core/shell particles by encapsulating a hydrocarbon‐based blowing agent. The core/shell polymers were characterized with respect to their chemical structure, thermal expansion, and morphology. The obtained particles, TEMs, showed an increasing onset expansion temperature with increasing content of MeMBL owing to the high glass transition temperature of PMeMBL. As a result, bio‐based/partially bio‐based TEMs are achieved with high thermal stability and expansion properties which can be tailored for various applications. [ABSTRACT FROM AUTHOR]

Rigid lignin foam is prepared by a baking method using kraft lignin as the sole source. The eco-forming process involved cold-pressing kraft lignin powder into a solid block, heating the solid block to form lignin foam, and finally curing and cooling the lignin foam to obtain an open-cell, rigid foam. Both adsorbed water and water generated from the dehydration of hydroxyl groups in the lignin served as the blowing agent in this baking method. It was found that as the moisture content of lignin decreased, the foam densities increased, the mean bubble sizes decreased, and the bubble size distributions became narrower. Foam morphology showed an open cell structure and a wide cell volume distribution. The results suggest that controlling the moisture content in raw lignin allows for the control of the pore structure of the lignin foam. Based on their unique properties, lignin foam materials hold great promise in many applications especially as core insulation materials for structural insulated panels (SIPs). [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation of the proposed method and the influence of a modified additive on foam concrete properties. X-ray diffraction analysis showed that the modified additive has a variable mineralogical composition, and the joint use of the components contributes to the synergistic effect, improving the processes of cement hydration. Microscopy of the foam concrete samples showed the presence of microcracks and micropores in samples both with and without the additive. However, the use of the additive significantly reduced their number and size, which indicates an improvement in the structure of the material. The strength values showed that the samples with the additive have high strength. In particular, the strength values of samples of type 3 at different stages of curing exceed those of samples of type 1 by 1.32–1.51 times and samples of type 2 by 1.07–1.10 times. The obtained strength values are 2.82–3.21 MPa for type 1, 3.64–4.04 MPa for type 2, and 4.39–4.84 MPa for type 3, which corresponds to grade D600. The evaluation of water absorption also confirmed the advantages of the proposed method and the additive, significantly reducing the water absorption of the samples and increasing their hydrophobicity. The obtained values of water absorption are 13.8–16.6% for type 1, 13.7–16.1% for type 2, and 9.5–11.2% for type 3. [ABSTRACT FROM AUTHOR]

Conventional manufacturing techniques of natural rubber foam (NRF) require long processing time besides producing closed cell structure, a property that limits the application of the NRF. The NRF produced via compression moulding (CPM) and microwave-convection oven heating techniques were compared in this study. The correlation between different processing techniques with the physical, morphological, and acoustic properties of NRF was examined. The results indicated that in all the processing techniques, an increase in the blowing agent (BA) led to a decrease in the density of the NRF. Heating the material sequentially with 16 parts per hundred (phr) of BA in a microwave oven at 1000 Watts, and then, in a convection oven at 150 ℃ produced NRF with a density of 0.23 g/cm3. In contrast, the NRF produced by CPM with 16 phr of BA had a density of 0.35 g/cm3. Scanning electron microscope analysis revealed that the NRF generated by CPM had fewer interconnected and more closed cells. On the other hand, sequential heating using microwave and convection heating techniques and vice versa led to the production of NRF with more open and interconnected cells. The prepared NRF was examined for acoustic properties. The results showed that the NRF produced by CPM at 12 and 16 phr of BA had the lowest ability to attenuate sound wave energy. This was due to the highly solid surface of the sample, which caused high sound wave reflection. Open and interconnected cells significantly improved the acoustic efficiency. These findings indicated that microwave-assisted heating techniques can modify the cellular structure of NRF and produce the material within a shorter period. [ABSTRACT FROM AUTHOR]

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials. [ABSTRACT FROM AUTHOR]

Bubble growth processes are highly complex processes, which are not only dependent on the foaming process parameters (temperature, pressure and blowing agent concentration) but also on the type and structure of the polymer used. Since the elongational viscosity at the bubble wall during bubble growth also depends on these influencing factors, the so-called transient elongational viscosity plays a key role in describing the gas bubble growth behavior in polymer melts. The model-based description of the transient elongational viscosity function is difficult due to its dependence on time, Hencky strain and strain rate. Therefore, representative viscosities or shear viscosity models are usually used in the literature to predict the bubble growth behavior. In this work, the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth is described holistically for the first time. This is achieved by extending the so-called molecular stress function (MSF) model by superposition principles (temperature, pressure and blowing agent concentration) and by using the elongational deformation behavior (Hencky strain and strain rate) at the bubble wall during the initial, and thus viscosity-driven, bubble growth process. Therefore, transient uniaxial elongational viscosity measurements are performed and the non-linear MSF model parameters of the two investigated polymers PS (linear polymer chains) and PLA (long-chain branched polymer chains) are determined. By applying the superposition principles and by changing the strain mode parameter to the equibiaxial case in the MSF model, the transient equibiaxial viscosity master curve is obtained and used to describe the bubble growth process. The results show that the extended MSF model can fully predict the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth processes. The bubble growth behavior over time can then be realistically described using the defined transient equibiaxial elongational viscosity function at the bubble wall. This is not possible, for example, with a representative viscosity and therefore clearly demonstrates the influence and importance of knowing the transient deformation behavior that prevails at the bubble wall during bubble growth processes. [ABSTRACT FROM AUTHOR]

Silicone elastomers are high-performance plastics. In the extrusion process, only high-consistency silicone rubbers were used. In order to reduce the cost and weight, silicone rubbers can be foamed during processing. In this study, high-consistency silicone rubber is processed with different physical and chemical blowing agents. The resulting reaction kinetics, as well as the mechanical and morphological properties, had been investigated and compared with each other. This showed that the chemical blowing agent significantly influenced the crosslinking reaction compared to the microspheres and the water/silica mixture tested, but it also achieved the lowest density compared to the physical blowing agents. When evaluating the foam morphology, it became clear that the largest number of pores was achieved with the microspheres and the largest pores when using the water/silica mixture. Furthermore, it has been shown that the different mechanisms of action of the blowing agents have a major influence on the mechanical properties, such as the micro shore hardness and the foam morphology. [ABSTRACT FROM AUTHOR]

Polyether block amide (PEBA) is an important thermoplastic polyester elastomer (TPE) owing to its low density and high resilience. Microcellular foaming can endow PEBA with significant potential in sports, medical, and industrial applications. However, with the current microcellular foaming technology, it remains challenging to obtain PEBA foams with stable shapes, which are critical for their mechanical properties. Therefore, microcellular foaming with CO2 and N2 as co‐blowing agents is utilized in this study to achieve mechanically robust PEBA foams by reducing the dimensional shrinkage. The introduction of N2 can effectively slow the diffusion rate of blowing agents into the air, providing support for the foam to resist external atmospheric pressure and effectively reducing the dimensional shrinkage of PEBA foams. Consequently, a stable foam shape is achieved with an expansion ratio of 7.9. Finally, the PEBA foams with excellent shrinkage resistance and mechanical properties are prepared, and the cell shrinkage mechanism is analyzed to study the effects of blowing agents and foaming methods on the structural evolution of TPE foams. This promising outcome paves way for their practical industrial applications. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, self‐healing natural rubber (SHNR) foam incorporating an intrinsic zinc thiolate ionic network was successfully prepared. The materials exhibited the ability to autonomously repair damage at room temperature without the need for external triggers. The investigation focused on the effect of sodium bicarbonate, employed as a blowing agent, on the self‐healing performance, as well as the physical and mechanical properties of the foam. Various concentrations of sodium bicarbonate (0, 1, 4, 8, and 10 phr) were employed. The conventional two‐roller mill was used for mixing and compounding, while compression molding was utilized for the vulcanization process. With increasing sodium bicarbonate concentration, the density, tensile strength, elongation at break, and compression set of the self‐healing NR foam were found to decreased. Conversely, the porosity, shrinkage, compressive strength, and water uptake of the SHNR foam increased as the concentration of sodium bicarbonate increased. Scanning electron microscopy analysis revealed that the optimal concentration of sodium bicarbonate (8 phr) resulted in smaller, finer, and more uniform porous structures. The self‐healing rubber foam incorporating 8 phr sodium bicarbonate exhibited improved properties in terms of tensile modulus, elongation at break, and tear strength, with healing efficiencies of 91.27%, 69.39%, and 83.99%, respectively. [ABSTRACT FROM AUTHOR]

A silicone rubber foam is prepared by introducing polydiborosiloxane (PDBS) into silicone rubber, and using expandable microspheres as blowing agents. The influences of the dual network structure with dynamic cross‐linking network on the silicone rubber foam is characterized by the cell size, mechanical properties and impact resistance. The cell size increases from 77 to 93 μm due to the introduction of a dynamic cross‐linking network which reduces foaming resistance. The elongation at break elevates from 277% to 574%, and the yield strength gradually decreases. The dynamic cross‐linking network also enhances the internal damping characteristic and energy absorption capacity of the foam. The impact resistance of silicone rubber foam is improved because of the synergistic effect of the dual network structure and the bubble structure. The research improves the performance of silicone rubber foam. [ABSTRACT FROM AUTHOR]

The utilization of polyols derived from renewable sources presents an opportunity to enhance the sustainability of rigid polyurethane (PUR) foams, thereby contributing to the advancement of a circular bioeconomy. This study explores the development of PUR rigid foams exclusively using polyols sourced from second-generation renewable biomass feedstocks, specifically depolymerized birch bark suberin (suberinic acids) and tall oil fatty acids. The polyols achieved a total renewable material content as high as 74%, with a suberinic acid content of 37%. Response surface modeling was employed to determine the optimal bio-polyol, blowing agents, and catalyst content, hence, optimizing the bio-based foam formulations. In addition, response surface modeling was applied to rigid PUR foam formulations based on commercially available petroleum-based polyols for comparison. The results, including apparent density (~40–44 kg/m3), closed cell content (~95%), compression strength (>0.2 MPa, parallel to the foaming direction), and thermal conductivity (~0.019 W/(m·K)), demonstrated that the suberinic acids-based rigid PUR foam exhibited competitive qualities in comparison to petroleum-based polyols. Remarkably, the bio-based rigid PUR foams comprised up to 29% renewable materials. These findings highlight the potential of suberinic acid-tall oil polyols as effective candidates for developing rigid PUR foams, offering promising solutions for sustainable insulation applications. [ABSTRACT FROM AUTHOR]