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1,1’-azodi(formamide) (azodicarbonamide – ADCA) is widely used as a blowing agent, a chemical substance designed to induce foaming processes. In Poland, ADCA is manufactured by a company specializing in the production of polyethylene foam bags and laminates used in various industries including home appliances, electronics, construction, furniture, automotive, and sports and leisure. The mechanism of action of ADCA involves thermal decomposition, resulting in nitrogen, carbon monoxide, as well as ammonia and carbon dioxide as the main gaseous decomposition products. These penetrate the polymer matrix, contributing to expansion and foaming properties. Most studies evaluating the relationship between occupational exposure and the development of allergic respiratory diseases focus on workers involved in ADCA production or its use as a blowing agent in plastics. The objective is to assess the respiratory sensitizing effects of ADCA in humans due to occupational exposure, based on literature data. The presented data confirm that long-term occupational exposure to ADCA can lead to persistent bronchial hyperreactivity symptoms in workers. 1,1’-azodi(formamide) can induce occupational asthma, with initial symptoms including nasal congestion, conjunctivitis, wheezing, and cough. Subsequently, symptoms such as chest tightness, dyspnea, and nocturnal cough attacks may appear, with a latency period of several years observed before symptom onset. In some cases, symptom progression was noted with continued ADCA exposure, while in others, exposure was discontinued after initial symptoms, preventing observation of symptom exacerbation. Prior exposure to allergens, such as working in bakeries, appears to accelerate symptom onset. Improvement in allergy symptoms has been noted during weekend breaks from work. There is no safe concentration identified for ADCA that would not result in adverse health effects for workers. A concentration of 0.036 mg/m 3 is considered the lowest observed adverse effect concentration, causing critical reduction in lung spirometric parameters. Med Pr Work Health Saf. 2024;75(5):455–473

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]

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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]

New generation intumescent coatings apply self-intumescing particles to induce expansion in a controlled manner. Various studies have investigated alkali silicate-based coatings due to their inherent expansion with the release of H 2 O. The presented work investigated the self-intumescing concept of alkali silicates as particles. A thorough study of inorganic alkali silicate particles as potential intumescent ingredients in passive fire protection systems was carried out by applying HSDM, TGA, FTIR, XRD, and SEM. Herein, particles of lithium-, sodium-, and potassium silicates were synthesized with varying silica-to-alkali oxide molar ratios and curing humidity. Subsequently, the hydration chemistry and thermal behavior were examined. The results revealed increased expansion potential with decreasing SiO 2 /M 2 O molar ratio (M = Na, Li, or K) in the range 3.1–7.4 and increasing curing humidity in the range 35, 50, and 90% RH. Previous studies have emphasized the effect of solid-bound H 2 O to induce intumescence. In this study, the influence of the softening of the silicate matrix and H 2 O release is highlighted to allow increased expansion potential. Here, the coupling of thermal analysis with microscopy suggests an intumescence mechanism in the order of 1) initial shrinkage due to loss of free and physical bound H 2 O, 2) sphere formation to minimize surface energy, 3) expansion as a result of H 2 O evolution and viscoelastic melt formation, and 4) second shrinkage due to sintering before 5) melting. The sodium alkali silicate particles with a SiO 2 /M 2 O molar ratio of 3.4 exhibited a timely softening of the silicate matrix from about 155 °C to provide a distinct spherical particle followed by ionic H 2 O evolution. As a result, hereof, hollow, spherical particles with relative solid expansions of up to 550% were obtained and maintained until a second shrinkage at 650 °C with a subsequent melting at 950 °C. In comparison, the imbalance in viscoelastic melt formation and H 2 O release of lithium- and potassium silicate particles resulted in less expansion. Considering the expansion potential and thermal behavior of the alkali silicate particles, it is suggested as a possible, sustainable intumescence ingredient. [ABSTRACT FROM AUTHOR]

In this study, polyurethane-polystyrene composites (RPURF-EPS) were obtained with the co-expansion method. This method consists of utilizing the heat of the exothermic reaction of polyurethane (PUR) formation to expand polystyrene beads (PSBs). The materials were obtained using polyurethane systems based on the selected blowing agents, such as cyclopentane, a mixture of fluorocarbons and water. The analysis of the foaming process was carried out using a special device called FOAMAT. The characteristic start, rise, gelation and curing times were defined. The rise profile, the reaction temperature, the pressure and the dielectric polarization were measured. The influence of selected blowing agents on the cell structure and physical–mechanical properties of reference rigid polyurethane foam (RPURF) and RPURF-EPS, such as apparent density, compressive strength and thermal conductivity, were evaluated. Based on the research, the blowing agents that have the most beneficial influence on the properties and structure of the composites and that provide the most efficient expansion of PSBs in a light porous composite were found. [ABSTRACT FROM AUTHOR]

The production of high-quality stainless steel strip and microcrystalline strip of special alloys directly from the melt on twin-roll continuous casters is an important strategic R&D topic in the steel industry. Analysis of the number and nature of published works on this topic in our country and abroad shows that research work is being completed. Experimental twin-roll casters built abroad have been tested in industrial conditions and put into operation. [ABSTRACT FROM AUTHOR]

Abstract A solid substance encircled by a three-dimensional network of voids not interconnected with each other is referred to as close-cell metal foam. The work is based on enhancing mechanical properties of aluminum base close-cell metal foam through the addition of reinforcing particles in varying percentages. Closed-cell aluminum foams with the addition of Mn (0.5 wt.%) and Mg (0, 1, 1.5, 2) were successfully prepared by the melt route method. Al-based metal foam’s morphology and mechanical behavior were examined in order to understand the impact of reinforcing elements. From the current work, it is inferred that the addition of reinforcing elements initially helped to increase the compressive strength as found in Foam-1, but further addition of Mg did not have any beneficial effects. It was found that the value of compression strength depends on foam density. The addition of reinforcing elements increases the length of the plateau which in turn increases the value of energy absorption. It is found that proper bonding of reinforcing particles helps in improving energy absorption. From the evaluation, it was found that besides the increase in density and variations in pores uniformity, Al + Mn (0.5wt. %) + Mg (1.5wt. %) Foam (Foam-1) was found to be superior among all other foams. It can also be concluded that by fixing the percentage of Mn by 1 wt%, the best results can be obtained by addition of 1.5 wt. % Mg in the melt. Further addition of Mg shows a detrimental effect on mechanical and physical properties.

The choice of blowing agent is very important in foaming processes. In an earlier work the use of molecular dynamics simulations for the estimation of the diffusion coefficients of different blowing agents was discussed at elevated temperatures above the melting point. Therein it was shown that these simulations can give valuable information on blowing agent diffusion in polypropylene. The aim of the recent work is to expand this discussion to the simulation of different influences like pressure, blowing agent mixtures and blowing agents with higher molecular weight at temperatures above the melting point of PP. First a pressure range applied on the combined system of polymer and blowing agent, reasonable for the foam processing is discussed and their influence on the diffusion coefficients for CO2 in polypropylene is evaluated via MD simulations. The next step is the investigation of the influence of mixing a blowing agent with a co-blowing agent. The last part is the presentation of diffusion coefficients for different organic solvents, namely 2-propanol, acetone, ethyl acetate and butyl acetate which could be used as potential co-blowing agents. For both, the change in pressure and the mixing of blowing agents for the systems in question only small influences on the diffusion coefficients was discovered. The results of the diffusion coefficients for the different organic solvents are compared to each other and with former results, considered different molecular structure, size and polarities and are found to be reasonable. [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. [ABSTRACT FROM AUTHOR]

Herein, a straightforward, adaptable, and cost‐effective approach has been proposed to realize the concept of dissolution of alumina in acidic aqueous media to fabricate porous alumina showing exceptional green machining properties and exhibiting good thermomechanical properties through in situ generated blowing agents and thermo‐foaming process. The process involves dissolving alumina in concentrated sulfuric acid to generate aluminum hydroxide and aluminum sulfate, which act as blowing agents to produce pores in the final structure through a decomposition process at elevated temperatures. By varying the concentration of deionized water and acidification using sulfuric acid, different alumina slurries are prepared. Sintering shrinkage is well countered through simultaneous consolidation and decomposition process during the heat treatment, and a minimum shrinkage of 0.88% is achieved. In addition to its pore‐forming properties, aluminum sulfate also provides strong binding effects to green bodies, contributing to their exceptional green machining properties. The resulting porous alumina exhibits a green flexural strength of up to 17 MPa, making it capable of bearing loads and forces during green machining. The sintered porous alumina fabricated in the study has a porosity range of 34.43%–59.24% and a flexural strength of 27.84–53.21 MPa. The prepared porous alumina also exhibits satisfactory thermal resistivity, with a minimum thermal conductivity of 1.23 W/m K, and has intra/intergranular space in the nano range. The coexistence of a combination of bimodal pores in a single monolithic matrix makes it exceptionally porous and suitable for an extensive spectrum of applications. [ABSTRACT FROM AUTHOR]

In this study, a reinforced geosynthetic cementitious composite mat (GCCM) with improved structural stability and reinforcement efficiency through yarn-in-lay technology was designed and manufactured. Additionally, a blowing agent was added to relax the cross-sectional reduction caused by the rapid curing and shrinkage for reduction of installation period. The impact resistance results showed a significant increase compared to the pre-reinforcement values. Through the analysis of blowing agent content, concrete filling ratio, and bending strength of the double raschel GCCM, optimal conditions were determined. Therefore, the double raschel GCCM showed improved flexural strength even after a short curing period of 10 days, along with excellent durability under environmental conditions. [ABSTRACT FROM AUTHOR]

The production of closed-cell metallic foams has been of interest to the scientific community and industry for decades, owing to their unique properties, which include high specific strength and stiffness, buoyancy, shock absorption, and crash worthiness. One of the approaches for their fabrication relies solely on the use of powders and is manifested in what has been referred to as the powder metallurgy (PM) route. This review discusses the underlying fundamentals of the process, and recent developments together with our current understanding. The effect of process parameters on the developed foam structure is reviewed for a range of metals, alloys, and metal matrix composites. Fundamental foaming mechanisms and characteristics are discussed. [ABSTRACT FROM AUTHOR]

A MATLAB program was developed to simulate urethane-forming reactions by solving over a dozen differential equations, energy balance, mass balance, and constitutive equations simultaneously. The simulation program was developed for half a decade to simulate the basic kinetics of polyurethane reactions and more complex phenomena that cannot be obtained in laboratories. In the current investigation, the simulation is applied to determine the limits of the performance of polyurethane foam formation. n-pentane, cyclohexane, and methyl formate were used as physical blowing agents, and water was used as a chemical blowing agent. The simulation code increases the accuracy of the results and makes the foam performance process less time- and money-consuming. Specifically, the MATLAB code was developed to study the impact of physical and chemical blowing agents at different loadings on the performance of rigid polyurethane foams. Experimental data were used to validate the simulation results, including temperature profiles, height profiles, and the tack-free time of urethane foam reactions. The simulation results provide a window for the proper type and the optimum amount range of different physical and chemical blowing agents. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the direct effect of using a blowing agent of siloxane (1, 1, 3, 3-tetramethydisiloxane) on the thermo-physical properties of the foamed epoxy. These properties are: density, glass-transition temperature, thermal conductivity and thermal expansion. The work has been conducted experimentally by manufacturing several specimens with different siloxane contents as: 0, 5, 10, 15 and 20 wt%. The properties of the specimens have tested under suitable conditions using different reliable instruments: differential scanning calorimetry, Lee-discs apparatus, and push rod dilatometer. Scanning electron microscope was used as well to analysis the morphological characteristics of the epoxy with respect to the pores generated by the blowing agent. In general, the foamed epoxy has shown different sizes of pores and extra crosslinking which leads to increase the glass-transition temperature of the material. Results show that the addition of 20% siloxane to the neat epoxy (as maximum) leads to: decreasing by 50% in bulk density, increasing by 20% in glass-transition temperature, decreasing by 30% in thermal conductivity, and decreasing by 75% in thermal expansion.

Industrial applications of pulses in various food products depend on pulse flour techno-functionality. To manipulate the techno-functional properties of yellow pea flour, the effects of flour particle size (small vs. large), extrusion temperature profile (120, 140 and 160 °C at the die) and air injection pressure (0, 150 and 300 kPa) during extrusion cooking were investigated. Extrusion cooking caused the denaturation of proteins and gelatinization of starch in the flour, which induced changes in the techno-functionality of the extruded flour (i.e., increased water solubility, water binding capacity and cold viscosity and decreased emulsion capacity, emulsion stability, and trough and final viscosities). In general, the large particle size flour required less energy input to be extruded and had higher emulsion stability and trough and final viscosities compared to the small particle size flour. Overall, among all of the treatments studied, extrudates produced with air injection at 140 and 160 °C had higher emulsion capacity and emulsion stability, making them relatively better suited food ingredients for emulsified foods (e.g., sausages). The results indicated air injection's potential as a novel extrusion technique combined with modification of flour particle size distribution and extrusion processing conditions to effectively manipulate product techno-functionality and broaden the applications of pulse flours in the food industry. [ABSTRACT FROM AUTHOR]

Commercialized polyurethane foam products for automobile steering wheels have been committed to the development of products with comprehensive properties such as low density, high production efficiency and environmental protection. Based on this, this article has launched a series of experiments to explore the effects of different types of chain extenders, blowing agents and catalysts on the mechanical properties, cell structure, skin and reactivity of self-skinning polyurethane foams for automobile steering wheels. The results show that the hardness and tensile strength of the foam gradually decrease with the chain growth of small molecular chain extenders (ethylene glycol, 1.3-propanediol, 1.4-butanediol), and the elongation at break increases gradually. The foaming agent formic acid is more conducive than water as it favors the formation of small but compact cells, thus dense skin. The catalytic efficiency of non-reactive catalysts (A1, KC101 and DabcoEG) is higher than that of reactive catalysts (LED-103, ZR-50, DPA). The theoretical research for the development of high-performance and high-efficiency polyurethane foam products for automobile steering wheels. [ABSTRACT FROM AUTHOR]

Polyurethane foams (PUFs) are a significant group of polymeric foam materials. Thanks to their outstanding mechanical, chemical, and physical properties, they are implemented successfully in a wide range of applications. Conventionally, PUFs are obtained in polyaddition reactions between polyols, diisoycyanate, and water to get a CO2 foaming agent. The toxicity of isocyanate has attracted considerable attention from both scientists and industry professionals to explore cleaner synthesis routes for polyurethanes excluding the use of isocyanate. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines in the presence of an external blowing agent or by self-blowing appears to be the most promising route to substitute the conventional PUFs process and to produce isocyanate-free polyurethane foams (NIPUFs). Especially for polyhydroxyurethane foams (PHUFs), the use of a blowing agent is essential to regenerate the gas responsible for the creation of the cells that are the basis of the foam. In this review, we report on the use of different blowing agents, such as Poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons for the preparation of NIPUFs. Furthermore, the preparation of NIPUFs using the self-blowing technique to produce gas without external blowing agents is assessed. Finally, various biologically derived NIPUFs are presented, including self-blown NIPUFs and NIPUFs with an external blowing agent. [ABSTRACT FROM AUTHOR]

Driven by global environmental issues, the development of green building materials has become an immediate focus. In this work, n‐pentane was used as an environmentally friendly blowing agent to prepare flame‐retardant rigid polyurethane foam (RPUF) with the addition of expandable graphite (EG) successfully, and the effect of n‐pentane content on flame retardancy and compressive properties of RPUF/EG composites was investigated through limit oxygen index (LOI), vertical burning test (UL‐94), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and compressive properties test. SEM results show that the content of EG and n‐pentane causes a change in the cell structure of RPUF. The change of the n‐pentane content has also an obvious effect on the thermal stability, flame retardancy, and specific compressive strength of RPUF/EG composites. In addition, the cell structure of RPUF matrix has an obvious influence on the distribution of EG in the composites, which indirectly affects the flame‐retardant efficiency of EG. This research explores the conditions for the application of environmentally friendly RPUF and expands its application prospects. [ABSTRACT FROM AUTHOR]

Nowadays, polymer foams are present in various areas of modern life. Having valuable and versatile features, they are utilized for insulation, packaging, sound absorption, cushioning and many other applications. Most of the commercially available polymer foams, whether rigid or flexible, are made from petrochemicals. Among these porous polymers, polyurethanes derived from highly hazardous isocyanates are dominant. Replacement of such foams with more environmentally safe materials holds great significance in the context of sustainability policy. Therefore, the utilization of molecules derived from biomass for the production of porous polymer foams is of considerable importance. This work focuses on the development of thermoset flexible foams based on plant oil, namely cottonseed oil. The polymeric matrix of the foams was prepared by the reaction of epoxidized cottonseed oil (ECO) with a cyclic anhydride in the presence of a catalyst, whereas the gaseous phase was generated by the addition of a chemical blowing agent. The morphology of the prepared foams was characterized using Scanning Electron Microscopy, while the internal structure of the foams was studied via Micro-Computed Tomography. The thermomechanical properties of foams were evaluated by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Possessing flexibility, softness, high porosity and shape memory ability, the prepared foams can be considered as potential cost-effective and eco-friendly options for flexible foams market: furniture, carper underlay, bedding. [Display omitted] • Manufacturing of foams without the use of isocyanates holds significant importance. • Biobased foams were fabricated using material derived from plant oil. • Foaming agent and accelerator were incorporated to generate gaseous phase. • The internal structure of the foams was meticulously examined. • Produced foams can be used in flexible foam market. [ABSTRACT FROM AUTHOR]

In this study, a reinforced geosynthetic cementitious composite mat (GCCM) with improved structural stability and reinforcement efficiency through yarn-in-lay technology was designed and manufactured. Additionally, a blowing agent was added to relax the cross-sectional reduction caused by the rapid curing and shrinkage for reduction of installation period. The impact resistance results showed a significant increase compared to the pre-reinforcement values. Through the analysis of blowing agent content, concrete filling ratio, and bending strength of the double raschel GCCM, optimal conditions were determined. Therefore, the double raschel GCCM showed improved flexural strength even after a short curing period of 10 days, along with excellent durability under environmental conditions.

This study used water as the physical blowing agent as well as microwave heating (MH) and convection heating (CH) to simultaneously foam and cure natural rubber foam (NRF). Various processing methods and parameters, such as single heating and sequential heating using a mix of CH and MH; were investigated. The correlation between these processing methods as well as different water loadings was then evaluated and compared in terms of physical appearance, density, and morphology. The NRF samples produced using sequential MH and CH (SMC) heating exhibited better shape and structure than samples produced using single heating of either CH or MH only as well as sequential CH and MH (SCM) heating at all water loadings. NRF samples with water loadings of 1.5 and 2.0 phr had a density of less than 0.1 g/cm3. The potential heating mechanism of all the heating methods explored in this study was proposed and discussed to further understand the microwave heating process. The findings of this study proved that water could be utilized as a physical blowing agent in the production of NRF products with microwave-assisted foaming.

Expanded thermoplastic polyurethane (ETPU) foam materials with superelasticity for footwear application were developed and investigated. ETPU foams with different ratios of CO2/N2 as foaming agents and ETPU foams prepared by pure nitrogen foaming with different kinds of foaming additives were prepared by supercritical (Sc) foaming technology, which further made into sheet forms through the steam molding process. TPU foam exhibits better cell structure, crystallization performance, and mechanical strength with the increased CO2 proportion. Further, the foams using 25% CO2–75% N2 and 50% CO2–50% N2, showed a lower density and excellent resilience and cyclic-compression performance. However, an increase of N2 ratio improves the dimensional stability and compression set of the foam. The introduction of foaming aids enhances the interaction between Sc-N2 and TPU. The ETPU foam prepared under the same conditions has a smaller density and a larger expansion ratio. Especially the ETPU foam prepared by Sc-N2 using monofluorodichloroethane as the foaming assistant as a co-blowing agent, the decrease in cell size (from 117.9 to 19.6 μm) and density (from 0.175 to 0.139 g/cm3) has observed. The study revealed the high potential of these materials in footwear applications and offered sound evidence for mass production in the industry.

Bio-based foams are growing and promising materials to replace petroleum-based foams because of their beneficial qualities including their affordability, outstanding fire resistance, high thermal insulation performance, eco-friendliness and the bio-sourced origin of the feedstock components. This study produced rigid bio-based foams using chemicals derived from plants, primarily from furfuryl alcohol and polyol derived from lignin. Lignin-based polyol and furfuryl alcohol were used to produce furan-lignin foams, which are free of formaldehyde and ozone damaging substances. Seven different furan-lignin foams were produced by substituting the toxic formaldehyde with a more eco-friendly glyoxal as a hardener while using diethyl ether and bentonite as blowing agent and filler respectively. Effects of these reagents on the quality of foams produced were assessed by varying their contents in the formulations. The properties of the produced bio-based foams such as compressive resistance, water absorption capacity, density and moisture content were evaluated. Further product characterizations: elemental composition, thermo-gravimetric analysis, Fourier transforms infrared spectroscopy and Scanning electron microscopy were carried out on the foams. The reaction leading to foam production was spontaneous at room temperature with an acid catalyst. Results showed that the concentrations of the blowing agent, hardener and filler, all had effects on the quality of the bio-based foams produced. Scanning electron microscopy results showed that the foams possessed closed cell morphologies, a rigid foam characteristic for good thermal and acoustic performance but modest water absorption, with cell widths of 10–200 μm, having high densities and strong compressive strengths as inherent characteristics. The results of the characterization indicated that the foams may be used as a thermal barrier or a support in construction and packaging applications because they had strong thermal stability, high compressive strengths, and a modest capacity to absorb water.

This work aimed to establish a simple method to produce additive-free triamcinolone acetonide (TAA) microspheres suitable for pulmonary delivery, and therefore more simple manufacturing steps will be warranted. The spray-drying process involved the optimization of the TAA feed ratio in a concentration range of 1–3% w/v from different ethanol/water compositions with/without adding ammonium bicarbonate as a blowing agent. Characterization of the formulas was performed via scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffraction. Our results indicated that the size and morphology of spray-dried TAA particles were dependent on the feed and solvent concentrations in the spray-dried formulations. Furthermore, adding the blowing agent, ammonium bicarbonate, did not produce a significant enhancement in particle characteristics. We prepared additive-free TAA microspheres and found that TAA formulation #1 had optimal physical properties in terms of diameter (2.24 ± 0.27 µm), bulk density (0.95 ± 0.05), tapped density (1.18 ± 0.07), and flowability for deposition during the pulmonary tract, from a centric airway to the alveoli as indicated by Carr's index = 19 ± 0.01. Hence, formulation #1 was selected to be tested for pharmacokinetic characters. Rats received pulmonary doses of TAA formula #1 and then the TTA concentration in plasma, fluid broncho-alveolar lavage, and lung tissues was determined by HPLC. The TAA concentration at 15 min was 0.55 ± 0.02 µg/mL in plasma, 16.74 ± 2 µg/mL in bronchoalveolar lavage, and 8.96 ± 0.65 µg/mL in lung homogenates, while at the 24 h time point, the TAA concentration was 0.03 ± 0.02 µg/mL in plasma, 1.48 ± 0.27 µg/mL in bronchoalveolar lavage, and 3.79 ± 0.33 µg/mL in lung homogenates. We found that TAA remained in curative concentrations in the rat lung tissues for at least 24 h after pulmonary administration. Therefore, we can conclude that additive-free spray-dried TAA microspheres were promising for treating lung diseases. The current novel preparation technology has applications in the design of preparations for TAA or other therapeutic agents designed for pulmonary delivery. [ABSTRACT FROM AUTHOR]

The possibility of synthesizing glass-ceramic geopolymer materials based on ash and slag waste generated during the combustion of coal fuel at power plants is considered. Compositions of charge have been developed, and synthesis of geopolymeric materials has been carried out. The density and uniformity of the porous structure of the obtained samples were analyzed, the substances—pore-forming agents—that have the highest foaming activity were selected, and the optimal amount of an alkaline activator for the synthesis of geopolymers was selected. The phase composition of the obtained samples was studied. [ABSTRACT FROM AUTHOR]

1,1'-azodi(formamide) (azodicarbonamide - ADCA) is widely used as a blowing agent, a chemical substance designed to induce foaming processes. In Poland, ADCA is manufactured by a company specializing in the production of polyethylene foam bags and laminates used in various industries including home appliances, electronics, construction, furniture, automotive, and sports and leisure. The mechanism of action of ADCA involves thermal decomposition, resulting in nitrogen, carbon monoxide, as well as ammonia and carbon dioxide as the main gaseous decomposition products. These penetrate the polymer matrix, contributing to expansion and foaming properties. Most studies evaluating the relationship between occupational exposure and the development of allergic respiratory diseases focus on workers involved in ADCA production or its use as a blowing agent in plastics. The objective is to assess the respiratory sensitizing effects of ADCA in humans due to occupational exposure, based on literature data. The presented data confirm that long-term occupational exposure to ADCA can lead to persistent bronchial hyperreactivity symptoms in workers. 1,1'-azodi(formamide) can induce occupational asthma, with initial symptoms including nasal congestion, conjunctivitis, wheezing, and cough. Subsequently, symptoms such as chest tightness, dyspnea, and nocturnal cough attacks may appear, with a latency period of several years observed before symptom onset. In some cases, symptom progression was noted with continued ADCA exposure, while in others, exposure was discontinued after initial symptoms, preventing observation of symptom exacerbation. Prior exposure to allergens, such as working in bakeries, appears to accelerate symptom onset. Improvement in allergy symptoms has been noted during weekend breaks from work. There is no safe concentration identified for ADCA that would not result in adverse health effects for workers. A concentration of 0.036 mg/m 3 is considered the lowest observed adverse effect concentration, causing critical reduction in lung spirometric parameters. Med Pr Work Health Saf. 2024;75(5):455-473., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Polyurethane foams obtained with low global warming potential and low ozone depletion potential blowing agent.

The purpose of this study is to investigate the direct effect of using a blowing agent of siloxane (1, 1, 3, 3-tetramethydisiloxane) on the thermo-physical properties of the foamed epoxy. These properties are: density, glass-transition temperature, thermal conductivity and thermal expansion. The work has been conducted experimentally by manufacturing several specimens with different siloxane contents as: 0, 5, 10, 15 and 20 wt%. The properties of the specimens have tested under suitable conditions using different reliable instruments: differential scanning calorimetry, Lee-discs apparatus, and push rod dilatometer. Scanning electron microscope was used as well to analysis the morphological characteristics of the epoxy with respect to the pores generated by the blowing agent. In general, the foamed epoxy has shown different sizes of pores and extra crosslinking which leads to increase the glass-transition temperature of the material. Results show that the addition of 20% siloxane to the neat epoxy (as maximum) leads to: decreasing by 50% in bulk density, increasing by 20% in glass-transition temperature, decreasing by 30% in thermal conductivity, and decreasing by 75% in thermal expansion. [ABSTRACT FROM AUTHOR]

This article aims to highlight the synthesis of foams from a blend of hydroxyurethane of castor oil and epoxy resin. An epoxidized castor oil of 4% oxirane oxygen was first converted to cyclic carbonate of castor oil at 120°C, 1 atm CO2 pressure and then it was reacted with three different aliphatic diamines to yield amine terminated Polyhydroxyurethane (PHU). Foams were prepared in a metal mould from the blend of PHU, epoxy resin, epoxy hardener and polymethylhydrogensiloxane blowing agent which releases hydrogen gas upon reaction with amine. FTIR and 1H NMR of cyclic carbonate of castor oil and PHU of castor oil were done to confirm their chemical structures. Optical microscopy and scanning electron microscopy of foams was done to assess their cellular morphology along with DSC and TGA to evaluate their thermal properties. Both flexible and rigid type of foams were synthesised in this study. Resilience of flexible foams was inspected using a ball rebound test and compression-recovery test while thermal insulation property was checked by measuring thermal conductivity, thermal diffusivity and R-values of rigid foams from heat transfer study using a heat transfer apparatus. [ABSTRACT FROM AUTHOR]

Although lightweight particleboards have been commercially available for years, they still have a number of disadvantages, including difficulty to process, brittleness, low impact strength, and other mechanical resistance. The aim of the paper was to determine the possibility of producing particleboards of reduced density (dedicated for furniture industry) as a result of using blowing agents from the group of hydrazides, dicarboxamides, or tetrazoles, which were modifiers of the adhesive resin used for bonding the particles of the core layer of three-layer particleboards. The concept presents the possibility of producing low-density particleboards in a standard technological process by modifying the adhesive resin, which has not been practiced by others until now. Analysis of the results of testing the particleboards properties with various types of modifiers (blowing agents), glue content (high 10%/12% and low 8%/10%), differing in glue dosing method, and different particle sizes allowed concluding that the most satisfactory effect was found in particleboards made of the variant modified with p-toluenesulfonyl hydrazide. This variant was characterised by the highest mechanical properties (bending strength, modulus elasticity, and internal bond strength) with high dimensional stability. The presented technology proposal can be applied in the industry. [ABSTRACT FROM AUTHOR]

In foaming processes, the blowing agent has a significant influence on the material behaviour and the necessary processing parameters. Low-density polypropylene foam sheets are usually produced with aliphatic hydrocarbons or alkanes as physical blowing agent. Due to the necessary safety precautions and the environmental impact, there is great interest in using alternative blowing agents such as CO2. The sole use of CO2 often leads to corrugation, open cells or surface defects on the foam sheet and therefore requires modifications to the process technology. For this reason, blowing agent mixtures based on CO2 and organic solvents are used for the production of foam sheets. For developing a process model describing the melt flow in the extrusion die and the formation of cells, specific material data like diffusion coefficients are necessary. For CO2 and N2 as sole blowing agent, experimental data exist in the literature. Since no experimental data are available for co-blowing agents such as ethanol at elevated temperatures as they occur in the foam process, these data were calculated using molecular dynamics (MD) simulations. The benefit of MD simulations lies in their ability to reduce the experimental effort and, in particular, to provide data in cases where this data is not available through experimental measurements. The calculated diffusion coefficient values are compared to experimental data from the literature and presented for CO2, N2 and ethanol in polypropylene. The calculated diffusion coefficients of CO2 and N2 are compared with literature results and agree well with them. For the ethanol molecules, the diffusion coefficient is compared relative to the both aforementioned ones considered the larger size of the ethanol molecule compared to N2 and CO2. The results of the diffusion coefficients for ethanol are reasonable compared to the values found for the other two molecules. [ABSTRACT FROM AUTHOR]

In the last decades, Aluminum foam has attracted many researchers and manufacturers due to its unique properties which find a lot of applications, especially in a lightweight structure. The current work aims to study the effect of adding calcined alumina to the melting aluminum on the final mechanical and microstructure of produced aluminum foam. Calcium carbonate was used as a foaming agent. The study reveals that calcination times/temperature have a significant effect on the final foam porosity. with increasing calcination time from 30 min to 90 min the foam density improved from 2.27 to 1.27 g/cm3, which consequently result in increase of samples porosity from 15.9 to 52.7%. also, the results from the compression test show that the variation of calcination time can be used to alter the energy absorption capacity of samples. Tested samples achieved the highest energy absorption of 128 MPa at a calcination time of 90 min. Also, the study reveals that calcination temperature has a significant effect on the final foam porosity. with increasing calcination temperature from 400 to 800°C, the foam density improved from 2.18 to 1.09 g/cm3, which consequently result in increase of samples porosity from 18.94 to 52.79%. Tested samples achieved the highest energy absorption of 325 MPa at a calcination temperature of 800°C. The increase in porosity is measured by ImageJ software, and the energy absorption test was carried out by a quasi-static compression test. These improvements produced material can be used in applications needs high energy absorption like automotive industry.

Amorphous shape memory polymer foams are currently used as components in vascular occlusion medical devices such as the IMPEDE and IMPEDE-FX Embolization Plugs. Body temperature and moisture-driven actuation of the polymeric foam is necessary for vessel occlusion and the rate of expansion is a function of physio-chemical material properties. In this study, concentrations of the chemical blowing agent for the foam were altered and the resulting effects on morphology, thermal and chemical properties, and actuation rates were studied. Lower concentration of chemical blowing agent yielded foams with thick foam struts due to less bubble formation during the foaming process. Foams with thicker struts also had high tensile modulus and lower strain at break values compared to the foams made with higher blowing agent concentration. Additionally, less blowing agent resulted in foams with a lower glass transition temperature due to less urea formation during the foaming reaction. This exploratory study provides an approach to control thermo-mechanical foam properties and morphology by tuning concentrations of a foaming additive. This work aims to broaden the applications of shape memory polymer foams for medical use. [ABSTRACT FROM AUTHOR]

Objective In view of the high salinity of oil reservoir formation water and the wide distribution of condensate oil content, a solid well flushing agent capable of withstanding high salinity and high condensate oil was developed to meet the well flushing of Gasi reservoir. Methods Based on the analysis results of oilfield water, the water contains more calcium ions, which has a great influence on the foaming ability and foam stability of anionic foaming agents, while nonionic, cationic and zwitterionic foaming agents have excellent salt resistance. The Weber stirring method was used to screen three types of foaming agents with excellent salt resistance. Results CAO-30 (zwitterionic ammonium oxide type) 9 CAB (zwitterionic betaine type), and YN-1 (non-ionic alkyl glycoside type) were selected, which have excellent salt tolerance. The three surfactants are compounded, and the combination of low surface tension, large foam volume and strong foam stability is preferred. Among them, the combination of zwitterionic betaine type and non-ionic alkyl glycoside foaming agent has synergistic effect, when using hydroxypropyl guar gum as a foam stabilizer, the foam stabilizing effect is good. The best ratio of foaming agent (mass ratio) is CAB : YN-1 : HPG= 6 : 9 : 5. The solid foaming agent was prepared with urea as fixative, the performance of it was evaluated. Conclusions The foaming agent has good compatibility with formation water, the maximum condensate oil concentration resistance is 30%, and the maximum temperature resistance is 80 °C 9 which has excellent ability to wash oil stains. [ABSTRACT FROM AUTHOR]

In the study, an investigation was made into the hydrolytic degradation behavior of the microporous polylactide (PLA) in the initial stage in three biological buffer solutions with various pH-simulating body fluids in comparison with pure PLA. Studies also include the analysis of selected mechanical properties and physical structures. A microporous PLA was obtained by melt extrusion using a chemical blowing agent. The rate of Mw decrease induced by hydrolysis over 35 days of microporous PLA was roughly comparable to the pure material. The rate of depolymerization was slightly accelerated at an acid pH due to acid-catalyzed hydrolysis at the end of the observed period. The mechanical analysis showed the influence of various pH on the obtained results. [ABSTRACT FROM AUTHOR]

The widespread use of aerated concrete in construction has led to the emergence of many types and compositions. However, additional research should fill theoretical gaps in the phenomenon of gas release during the formation of the structure of aerated concrete. Based on theoretical analysis and experimental studies, the article proposes a mathematical model of the swelling process based on the physicochemical laws of convection and molecular diffusion of hydrogen from a mixture and the conditions of swelling, precipitation, and stabilization of the mixture. An improved method for the manufacture of aerated concrete is proposed, which consists of introducing cement pre-hydrated for 20–30 min into the composition of the aerated concrete mixture and providing improved gas-holding capacity and increased swelling of the mixture, reducing the average density of aerated concrete up to 29% and improving heat-shielding properties up to 31%. At the same time, the small dynamics of a decrease in the strength properties of aerated concrete were observed, which is confirmed by an increased structural quality factor (CSQ) of up to 13%. As a result, aerated concrete has been obtained that meets the requirements of environmental friendliness and has improved mechanical and physical characteristics. Economic efficiency is to reduce the cost of production of aerated concrete and construction in general by about 15%. [ABSTRACT FROM AUTHOR]

This study examines the isolated impact of temperature on the accelerated aging of closed-cell foam insulation materials. Laboratory aging of closed-cell foams was conducted at three temperatures: −10, 23 and 50 °C. This was to cover the range of the material's in-service range within a Canadian climate. Three polyisocyanurate foam and one extruded polystyrene foam insulations were considered in the study. The three polyisocyanurate foam products tested showed significant variability in polynomial functions at lower mean temperatures when newly manufactured; however, these differences were found to diminish over time. Thermal conductivity decreased between 0% and 17% depending on mean temperature following equivalent 5-year aging at 23 °C. Aging polyisocyanurate specimens at −10 °C was found to decrease rate of change in thermal conductivity by approximately 5% compared to aging at 23 °C when measured at a mean temperature of 24 °C, while aging at 50 °C had a smaller impact. However, at mean temperatures below the beginning of condensation point, there was greater variability in the impact of aging temperature. For the extruded polystyrene, thermal conductivity decreased between 8% and 10% following equivalent 5-year aging at 23 °C and displayed a linear relationship with a 23% difference in thermal conductivity between −10 °C and 40 °C. [ABSTRACT FROM AUTHOR]

This study used water as the physical blowing agent as well as microwave heating (MH) and convection heating (CH) to simultaneously foam and cure natural rubber foam (NRF). Various processing methods and parameters, such as single heating and sequential heating using a mix of CH and MH; were investigated. The correlation between these processing methods as well as different water loadings was then evaluated and compared in terms of physical appearance, density, and morphology. The NRF samples produced using sequential MH and CH (SMC) heating exhibited better shape and structure than samples produced using single heating of either CH or MH only as well as sequential CH and MH (SCM) heating at all water loadings. NRF samples with water loadings of 1.5 and 2.0 phr had a density of less than 0.1 g/cm3. The potential heating mechanism of all the heating methods explored in this study was proposed and discussed to further understand the microwave heating process. The findings of this study proved that water could be utilized as a physical blowing agent in the production of NRF products with microwave-assisted foaming. [ABSTRACT FROM AUTHOR]

This work investigated the effects of a radiation-protective filler, namely bismuth oxide (Bi2O3), and blowing agents, namely azodicarbonamide (ADC) and oxy-bis (benzene sulfonyl) hydrazide (OBSH), on gamma attenuation and the mechanical, physical, and morphological properties of cellular natural rubber (NR) composites for potential use as light-weight and lead-free gamma-shielding materials. The contents of Bi2O3 were varied from 100 to 300 and 500 parts per hundred of rubber by weight (phr) and the contents of ADC or OBSH were varied from 0 to 8 and 16 phr. The results indicated that the addition of Bi2O3 enhanced the overall gamma-shielding ability, density, tensile modulus, and hardness (Shore OO), but lowered the tensile strength and elongation at break. On the other hand, the addition of ADC or OBSH resulted in decreases in the density, linear attenuation coefficient (μ), and overall tensile properties but an increase in the mass attenuation coefficient (μm), with ADC producing better mechanical properties than samples with OBSH. In addition, investigations on the properties of the cellular Bi2O3/NR composites under additional 35 kGy and 70 kGy gamma irradiation revealed that the irradiated samples had increased density, tensile modulus, and hardness (Shore OO), but decreased tensile strength, elongation at break, and μm after such ageing. In conclusion, the overall results suggested that the developed cellular Bi2O3/NR composites not only had efficient and promising gamma-shielding and mechanical properties but also offered comfort and light-weight to users, which could potentially reduce discomforts caused by wearing heavier conventional radiation-protective equipment. [ABSTRACT FROM AUTHOR]

Polyurethane foam is an insulating material, which is adopted in various industrial fields owing to its high compressive strength, low thermal conductivity, and excellent impact resistance. The most important additive in the synthesis process of the polyurethane foam is the blowing agent because it significantly affects the cell structure and density. HFC‐245fa, the most widely used blowing agent, is expected to be terminated under strict environmental regulations owing to its high global warming potential. This study synthesizes a new eco‐friendly polyurethane foam with HCFO‐1223zd in the density range of 90 to 190 kg/m3. After the synthesis process, the microstructural morphology of the HCFO‐1223zd blown polyurethane foam was observed using scanning electron microscopy. Additionally, the insulation performance was compared to conventional polyurethane foam. Furthermore, mechanical characteristics were investigated at 20 and −163°C temperatures. The results show that the HCFO‐1233zd blown polyurethane foam has superior mechanical and thermal properties compared to the conventional blowing agents. [ABSTRACT FROM AUTHOR]

Porous polymer films have been investigated for various applications. The conventional method forms microporous structures throughout a film. This paper presents a new process for forming micro/nano-porous patterns on a polyimide membrane surface using a laser and a blowing agent only in selected areas. A blowing agent was mixed in a polyimide, and the mixture was then irradiated with a laser to instantaneously heat it to the decomposition temperature of the blowing agent. Subsequently, micro/nano-porous patterns were created only in regions irradiated with the laser owing to the explosion of the blowing agent. The micro/nano-porous patterns were fabricated using 355-nm ultraviolet pulse laser processing. The pores of the porous structures were closed or open, depending on the quantity of blowing agent, laser fluence, and pulse overlap ratio. The experimental results showed that the pore density, pore size, and processing time could be adjusted. In addition, porous patterning was formed selectively and locally. Recently, micro-/nano porous patterned films have been widely used as absorbents, support cells, and sensors in industrial fields and they have considerable application potential in various fields. [ABSTRACT FROM AUTHOR]

Falling on the floor has been one of the most common causes of breaking a bone. Falls in senior homes and care facilities can lead to immobility symptoms and treatments. Rubber flooring is a great alternative for fall protection. Thus, this study aimed to investigate the effects of organic blowing agents (dinitroso pentamethylene tetramine and azodicarbonamide) on the physical and mechanical properties of natural rubber foam used for laminated floor tiles. The curing temperatures were also examined in the range of 140–160 oC. From the experimental results, the blowing agent was an important component added to the rubber foam layer at various contents and temperatures. The compression set increased when curing temperatures and adding blowing agent increased. With an increase in the curing temperature, the elongation at break decreased. The findings indicated that the mechanical properties of natural rubber foam were significantly affected by the kind of blowing agent and the curing temperature. Finally, an optimal energy absorption was found in the dinitroso pentamethylene tetramine condition with 3 phr and the curing temperature of 160°C, which offers the maximum energy absorption value of 110 J. [ABSTRACT FROM AUTHOR]