Search

This research aims to enhance fibre-matrix adhesion in bio-based fibre-reinforced polyolefins without using adhesion promoters. The primary focus is to establish a cross-linking mechanism between cellulose fibres and polyethylene by applying UV irradiation to a UV-transparent matrix and UV-absorbing fibres. The influence of UV treatment on the composite properties is evaluated by tensile, interfacial and interlaminar shear strength tests. The UV irradiation decreases the critical fragment length in single fibre fragmentation tests, indicating an improved fibre-matrix adhesion. The UV-irradiated composites’ tensile strength and Young’s modulus are found to be ~10% (for 3- and 8-minute irradiation) and ~50% (for 8-minute irradiation), respectively, higher than those of the untreated samples. Furthermore, the UV irradiation leads to an improvement in the interlaminar shear strength by 25%. The variation of the UV-irradiation time (3 min and 8 min) and the comparison of the properties of semi-finished composite sheets and composites also reveal chemical and physical changes in the regenerated cellulose fibres due to heat adsorption. The proposed mechanism of interfacial crosslinking is confirmed by FTIR spectroscopy. The results suggest an approach to overcome poor compatibility between hydrophobic polyolefin matrix and hydrophilic cellulose-based fibres, resulting in adhesive-free bio-based composites. [ABSTRACT FROM AUTHOR]

Although Ziegler-Natta (Z-N) polyolefins have been widely used as raw materials to produce pharmaceutical or food packaging, the migration of acid scavengers, an additive usually introduced in Z-N polyolefins, from the packaging to its contents has not been reported. In this work, the migration of the two most used acid scavengers, calcium stearate (CaSt2) and zinc stearate (ZnSt2), from a Z-N polypropylene random copolymer (PPR) into water during autoclaving at 121 °C were comparatively investigated. It was found that, for PPR plates containing 0.1 wt% CaSt2 or ZnSt2 (PPR-0.1CaSt2, PPR-0.1ZnSt2, respectively), the concentration of migrated calcium ion into water increased with autoclaving time, while that of zinc ion was much lower at same treatment durations and did not show a significant increase with treatment time. Interestingly, after removing all plates and acidification treatment, a considerable amount of stearic acid was detected in sterilized water for PPR-0.1ZnSt2, but no such significant stearic acid was detected in sterilized water for PPR-0.1CaSt2. Based on the structural evolution of the two soaps upon heating, possible mechanisms for the different migration behavior of CaSt2 and ZnSt2 from PPR into water during autoclaving treatment were proposed. Our results suggest that the migration issue of acid scavengers is worthy of attention in pharmaceutical packaging materials produced from Z-N polyolefins. [ABSTRACT FROM AUTHOR]

Synthetic fibres cover most of the textile market, but their value chain is almost entirely linear. Common raw materials are non-renewable and oil-derived while requiring large amounts of (toxic) chemicals and energy for their processing into final products. In addition, synthetic textiles are usually non-biodegradable polymers; therefore, sustainable approaches for their depolymerisation into reusable monomers have not been implemented yet. As a result, most post-consumer synthetic textile waste ends up being landfilled, dispersed in the environment or incinerated, thus contributing significantly to global pollution. A possible solution to this issue is the design and use of advanced catalysts for their chemical recycling. This manuscript reviews the most significant approaches that appeared in the literature in the time span of 2015–2024, covering the selective depolymerisation process of synthetic waste textile to added-value reusable monomers using chemical catalysts. Unselective processes, for example, to produce fuel mixtures, biocatalytic methods and depolymerisation of polyolefins are not covered. The general aspects of the catalytic depolymerisation of synthetic polymers are briefly discussed, and the catalytic chemical recycling of synthetic textiles is detailed by the polymer type. While contributing to the overall achievement of the sustainable development goals, chemical recycling of synthetic textile waste may represent a useful strategy toward the circularity of the textile sector, which is almost unexplored. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) inorganic fillers can significantly improve the properties of polyolefins and broaden their application areas. In this study, high‐performance polyethylene (PE)/siloxene nanocomposites were prepared by in situ polymerization using layered siloxene‐supported vanadium (V)‐based catalysts. The siloxene‐supported V‐based catalysts have highly dispersed active sites and excellent catalytic performance for ethylene polymerization compared to VOCl3 catalysts. The catalytic activity of the siloxene‐supported V‐based catalysts for the polymerization of ethylene was significantly better than that of the VOCl3 catalysts at the same catalyst feed. During in situ polymerization, the layered siloxene fillers exhibited uniform dispersion in the PE matrix. Moreover, the addition of a very small amount (1.12 wt%) of siloxene filler significantly improved the thermal stability and mechanical performance of PE. Therefore, this study presents an effective method to fabricate PE with excellent properties. [ABSTRACT FROM AUTHOR]

Diimine Pd catalysts have been known to promote the living polymerization of olefins. Treatment of the living polyolefin with carbon monoxide followed by the addition of alcohols or amines results in alkoxycarbonylation or aminocarbonylation of the living chain end. The alkoxycarbonylation or aminocarbonylation using polymers having hydroxy or amino terminal group leads to direct linking of the end‐functionalized polymer with the living polyolefins. The introduction of hydroxy, amino, and 2‐bromoisobutyrate functional groups on the terminal of the polyolefin is also possible by the alkoxycarbonylation or aminocarbonylation. The end‐functionalized polyolefin having 2‐bromoisobutyryl terminal group acts as a macroinitiator for living radical polymerization of styrene to give poly(olefin‐block‐styrene). [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon‐carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low‐molecular‐weight (LMW) PE using an enzyme cascade that included a catalase‐peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m‐chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram‐scale pretreated polymers, GC‐MS and weight loss determinations confirmed ~27 % polymer conversion including the formation of medium‐size functionalized molecules such as ω‐hydroxycarboxylic acids and α,ω‐carboxylic acids. Additional analyses of LMWPE‐nanoparticles using AFM showed that enzymatic depolymerization reduced the sizes of these mCPBA‐ and enzyme‐treated LMWPE‐nanoparticles. This multi‐enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio‐based recycling methods for polyolefin waste. [ABSTRACT FROM AUTHOR]

In the present study, a novel crystalline nucleating agent for isotactic polypropylene (PP) comprising the calcium salt of 4‐methyl‐cyclohexane‐1,2‐dicarboxylic acid (MHPA‐Ca) is developed. The performance of the nucleating agent is evaluated by determining the crystallization temperature and isothermal crystallization period of the PP by differential scanning calorimetry, and comparing them with those obtained using the calcium salt of cyclohexane‐1,2‐dicarboxylic acid (HHPA‐Ca), which is one of the most effective nucleating agents for PP. The results demonstrate that the nucleating ability of MHPA‐Ca is much stronger than that of HHPA‐Ca. Consequently, an injection‐molded plate containing MHPA‐Ca has a high degree of chain orientation. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in materials that combine the advantages of glass and polymer materials. Such a combination results in a kind of hybrid glass-polymer optics that meets the requirements for high-quality imaging in various environmental conditions. So far, the literature on these materials is quite scarce. This article is an attempt to review the most important reports on the topic of available polymers with optical properties, dividing them into groups, i.e. synthetic optical polymers (including polymethylmethacrylate, polyethylene terephthalate, polypropylene, cyclic olefin copolymers and polyolefin elastomers) and biopolymers (including polylactide and gelatin). A separate place and chapter is given to transparent CR-39 plastic and the issue of individual dosimetry for radon detection. Moreover, testing methods for measuring the most important optical properties of polymers and their major applications are briefly discussed. [ABSTRACT FROM AUTHOR]

Polyolefins, widely used for packaging, construction, and electronics, facilitate daily life but cause severe environmental pollution when discarded after usage. Chemical recycling of polyolefins has received widespread attention for eliminating polyolefin pollution, as it is promising to convert polyolefin wastes to high-value chemicals (e.g., fuels, light olefins, aromatic hydrocarbons). However, the chemical recycling of polyolefins typically involves high-viscosity, high-temperature and high-pressure, and its efficiency depends on the catalytic materials, reaction conditions, and more essentially, on the reactors which are overlooked in previous studies. Herein, this review first introduces the mechanisms and influencing factors of polyolefin waste upcycling, followed by a brief overview of in situ and ex situ processes. Emphatically, the review focuses on the various reactors used in polyolefin recycling (i.e., batch/semi-batch reactor, fixed bed reactor, fluidized bed reactor, conical spouted bed reactor, screw reactor, molten metal bed reactor, vertical falling film reactor, rotary kiln reactor and microwave-assisted reactor) and their respective merits and demerits. Nevertheless, challenges remain in developing highly efficient reacting techniques to realize the practical application. In light of this, the review is concluded with recommendations and prospects to enlighten the future of polyolefin upcycling. [ABSTRACT FROM AUTHOR]

The surge in global plastic production, reaching 400.3 million tons in 2022, has exacerbated environmental pollution, with only 11% of plastic being recycled. Catalytic recycling, particularly through hydrogenolysis and hydrocracking, offers a promising avenue for upcycling polyolefin plastic, comprising 55% of global plastic waste. This study investigates the influence of water on polyolefin depolymerization using Ru catalysts, revealing a promotional effect only when both metal and acid sites, particularly Brønsted acid site, are present. Findings highlight the impact of Ru content, metal-acid balance, and their proximity on this interaction, as well as their role in modulating the isomerization process, affecting product selectivity. Additionally, the interaction facilitates the suppression of coke formation, ultimately enhancing catalyst stability. A comprehensive techno-economic and life cycle assessment underscores the viability and environmental benefits of the process, particularly in the presence of water. These insights advance understanding and offer strategies for optimizing polyolefin plastic recycling processes. Catalytic hydrogenolysis and hydrocracking present a promising approach for upcycling polyolefin plastics. Here, the authors highlight the role of water in catalytic plastic upcycling, emphasizing that catalysts with an optimal metal-acid balance significantly improve polyethylene depolymerization when water is present. [ABSTRACT FROM AUTHOR]

The control of the regioselectivity of metal‐catalyzed α‐olefins polymerization is of everlasting interest. Most nickel and palladium catalysts show high regioselectivity involving 2,1‐insertion of α‐olefins and 1,ω‐enchainment chain‐straightening, especially α‐diimine nickel catalysts. In this contribution, we report extremely rare regioselective chain‐straightening polymerization of α‐olefins through 2,ω‐enchainment using unsymmetrical amine–imine nickel catalysts. The polymerizations of α‐olefins (1‐hexene, 1‐octene, and 1‐decene) were studied in detail, and the effects of catalyst structure, reaction temperature, and monomer concentration on the polymerization activity and the regioselectivity were examined. The unsymmetrical N‐substituents of the amine–imine nickel catalysts play a crucial role in the regioselectivity. High regioselectivity involving 80.4% 1,2‐insertion and 84.5% 2,ω‐enchainment is realized to produce amorphous polyolefins without melting temperatures. [ABSTRACT FROM AUTHOR]

Additives have been critical to the growth of flexible packaging since its inception nearly 100 years ago. Additives help tailor the performance of new materials to meet packaging needs and to efficiently run on film converting and packaging equipment. Examples include antioxidants for thermo‐oxidative stability during extrusion, slip and antiblock agents to improve film handling and frictional properties, polymer process aides (PPAs) to delay the onset of flow instabilities and increase output, pigments for coloring films and creating light barrier, antifog agents to improve wetting of film surfaces, antistat agents to reduce static charge, and nucleating agents for increasing the rate of crystallization and controlling crystalline morphology. This paper provides a brief history of the development and use of additives in flexible packaging, focusing on polyolefins. It then looks forward at new challenges and opportunities for additive development. One area is regulatory driven, most recently replacing per‐and polyfluoroalkyl substances (PFAS)‐containing PPAs with non‐PFAS technology. The industry has had to respond very rapidly to changing regulations and introduce new technology. The challenge is understanding the impact of the new technology on performance. A second area is sustainability where additives will be critical for upgrading the performance of mechanically recycled post‐consumer packaging waste, redesigning flexible packaging structures so that they can be recycled in the PE‐stream, and using bio‐based or compostable polymers. New research methods such as high throughput experimentation, artificial intelligence and computer modeling and simulation will likely accelerate additive development in the future. Highlights: Additives are critical for meeting flexible packaging performance needs.Additives improve surface and bulk properties and processability.Replacing PFAS‐containing process aides is a current area of focus.Sustainability is driving new opportunities for additive development.New research tools will help accelerate additive development. [ABSTRACT FROM AUTHOR]

Composites of polypropylene (PP) and calcium lactate (CL) with a constant weight percentage of 60% and 40%, respectively, were compounded with 3, 5 and 7 phr of epoxidized soybean oil (ESO) plasticizer using an internal mixer. The testing samples were prepared using an injection molding technique. The effects of the mold temperature and annealing treatment on the morphological and mechanical properties of PP-based composites using polarized optical microscopy (POM), differential scanning calorimetry (DSC), universal testing machines (UTM), and impact tester were performed. The results showed a remarkable increase in the elongation-at-break and impact strength, but a noticeable decrease in tensile strength and stiffness with increasing ESO contents. The experimental results also indicated that the higher mold temperature significantly improved the tensile strength and stiffness of samples due to an increase in spherulite size for neat PP, PP/CL composite and PP/CL composite with 3 phr of ESO. Additionally, annealing treatment enhanced the tensile and impact strengths of both neat PP and PP/CL composite, which was attributed to the increase in the crystal perfection and degree of crystallinity. These findings suggested that mechanical improvements using high mold temperature and annealing treatment were confined to the incorporation of an ESO plasticizer. The resulting performance of the plasticized PP composites after thermal treatment was described by two possibilities: the loss in the adhesion between the components and the migration of plasticizer.

Charge injection at metal/polymer interfaces is a critical process in many technological devices, including high voltage capacitors and cables in which polyolefin materials, such as polyethylene (PE) and polypropylene (PP), are often used as insulation materials. We use simulations based on density-functional theory to study charge injection at aluminum/PE and aluminum/PP interfaces. Specifically, we investigate the influence of incorporating a variety of polar chemical impurities at the PE and PP chain ends on electron and hole injection barriers. Crucially, we account for the effect of thermal disorder by considering ensembles of thousands of interface structures obtained from ab initio molecular dynamics trajectories at 373 K. We show that the mean injection barrier can change by up to 1.1 eV for Al/PE and 0.6 eV for Al/PP, as compared to the pristine case, depending on which chemical impurity is introduced. We also show that the spread of injection barriers from thermal fluctuations also depends strongly on the chemistry of the impurity. The observed trends can be understood with a simple model based on thermal fluctuations of the dipole moment density associated with the chemical impurity at the interface. We further verify this model by considering larger interface models with lower impurity densities. Our results demonstrate that small chemical modifications, which may arise from oxidation, for example, have a significant influence on charge injection barriers in metal/polyolefin interfaces. [ABSTRACT FROM AUTHOR]

Mitigating plastic waste pollution and reducing reliance on fossil resources have become more and more important. Propylene is one of the most crucial starting materials in chemical and petrochemical industries. Therefore, these industries can derive substantial benefit from the recovery of propylene from plastic waste in terms of enhancing sustainability. Thermochemical conversion process, such as pyrolysis, gasification, and steam cracking, is regarded as a representative effective approach to recover propylene from plastic waste (e.g., polyolefins and plastic mixtures). This work aimed to promote the adoption of the propylene recovery strategy in chemical/petrochemical sectors with highlighting the performance of various thermochemical conversion processes to obtain propylene from plastic waste. To this end, reputable peer-reviewed journals were searched with relevant keywords and strictly screened to find the data about the propylene recovery yield, the type of plastic waste, the type of process, and process operating conditions. Furthermore, current limitations are presented concerning future research towards improving the viability of thermochemical recovery of propylene from plastic waste. This review not only offers helpful guidelines on the development of effective platforms to produce value-added monomeric chemicals from plastic waste but also encourages the chemical industry to adopt the waste-upcycling approach on a wider scale.

This study compares the efficiency of commercially available sorbitol-based clarifying agent (NA) and varying amounts of long chain-branched polypropylene (LCBPP) acting as a specific α-nucleating agent for linear polypropylene (PP). The sorbitol-based clarifying agent, 1,3;2,4-bis(3,4-dimethyl benzylidene)sorbitol (Millad 3988), in concentration 0.2 wt%, and LCBPP in the concentration of 1, 2, 5 and 10 wt% were mixed into PP. The comparison of the effect of NA and long branches under isothermal conditions on the crystallization process, crystallinity and polymorphic composition was realized by differential scanning calorimetry and wide-angle X-ray scattering. The addition of long chain-branched polypropylene, even at the lowest concentration, performs better at higher crystallization temperatures and has a superior effect on the crystallization process, crystallization rate and overall crystallization than the addition of NA.

Herein, we report a selective photooxidation of commodity postconsumer polyolefins to produce polymers with in‐chain ketones. The reaction does not involve the use of catalyst, metals, or expensive oxidants, and selectively introduces ketone functional groups. Under mild and operationally simple conditions, yields up to 1.23 mol % of in‐chain ketones were achieved. Installation of in‐chain ketones resulted in materials with improved adhesion of the materials and miscibility of mixed plastics relative to the unfunctionalized plastics. The introduction of ketone groups into the polymer backbone allows these materials to react with diamines, forming dynamic covalent polyolefin networks. This strategy allows for the upcycling of mixed plastic waste into reprocessable materials with enhanced performance properties compared to polyolefin blends. Mechanistic studies support the involvement of photoexcited nitroaromatics in consecutive hydrogen and oxygen atom transfer reactions. [ABSTRACT FROM AUTHOR]

Mitigating plastic waste pollution and reducing reliance on fossil resources have become more and more important. Propylene is one of the most crucial starting materials in chemical and petrochemical industries. Therefore, these industries can derive substantial benefit from the recovery of propylene from plastic waste in terms of enhancing sustainability. Thermochemical conversion process, such as pyrolysis, gasification, and steam cracking, is regarded as a representative effective approach to recover propylene from plastic waste (e.g., polyolefins and plastic mixtures). This work aimed to promote the adoption of the propylene recovery strategy in chemical/petrochemical sectors with highlighting the performance of various thermochemical conversion processes to obtain propylene from plastic waste. To this end, reputable peer-reviewed journals were searched with relevant keywords and strictly screened to find the data about the propylene recovery yield, the type of plastic waste, the type of process, and process operating conditions. Furthermore, current limitations are presented concerning future research towards improving the viability of thermochemical recovery of propylene from plastic waste. This review not only offers helpful guidelines on the development of effective platforms to produce value-added monomeric chemicals from plastic waste but also encourages the chemical industry to adopt the waste-upcycling approach on a wider scale. [ABSTRACT FROM AUTHOR]

Plastic waste is an underutilized resource that has the potential to be transformed into value-added materials. However, its chemical diversity leads to cost-intensive sorting techniques, limiting recycling and upcycling opportunities. Herein, we report an open-loop recycling method to produce graded feedstock from mixed polyolefins waste, which makes up 60% of total plastic waste. The method uses heat flow scanning to quantify the composition of plastic waste and resolves its compatibility through controlled dissolution. The resulting feedstock is then used to synthesize blended pellets, porous sorbents, and superhydrophobic coatings via thermally induced phase separation and spin-casting. The hybrid approach broadens the opportunities for reusing plastic waste, which is a step towards creating a more circular economy and better waste management practices. [ABSTRACT FROM AUTHOR]

This study solved a set of equations to verify the dynamic optimal conditions of nonthermal plasma (NTP)-chemical conversion of solid polyolefin wastes into liquid petroleum hydrocarbons. Furthermore, a novel optimisation model was validated with non-linear experimental conditions to assess the quantitative relationship between the process variables responsible for the degradation rate of wastes. The central composite design (CCD) experimental design was developed based on the Response Surface Model (RSM) technique. These techniques significantly improved the model predictions because of the more-detailed electrochemical description. Experiments were conducted in an in-house-designed and -developed NTP system with advanced data acquisition schemes. Both experimental and the numerical findings exhibited a good agreement, and the results indicated that the electrical factors of NTP could significantly affect the conversion yield (Yconv%) of solid polyolefin-derived wastes to liquid hydrocarbons. Additionally, the model investigation indicated that factors such as power discharge ( x 1 ), voltage intensity ( x 2 ), and reaction retention time (RTT) ( x 3 ) significantly influenced the conversion yield. After optimisation, a maximum conversion percentage (Yconv%) of ≈93% was achieved. The findings indicated that this recommended framework could be effectively employed for scaling the plasma synergistic pyrolysis technique for generating the maximal Yconv% of plastic wastes to yield an oil. Thereafter, the analysis of variance (ANOVA) technique was applied to examine the accuracy of the developed structure in order to upgrade this laboratory-scale processes to an industrial-scale process with >95% effectiveness. The calorific value of the produced oil was seen to be from 43,570.5 J/g to 46,025.5 J/g due to changes of the arrangements of the process factors, which specified that the liquid hydrocarbons showed similar characteristics like commercial diesel in this respect. [ABSTRACT FROM AUTHOR]

This study aims to establish a systematic approach for characterizing recycled polyolefins of unknown composition, with a specific focus on predicting their performance in film extrusion. We explore various characterization techniques, including differential scanning calorimetry (DSC), Fourier‐transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and rheometry to assess their effectiveness in identifying the polyethylene (PE) fractions within polypropylene (PP) recyclates. By integrating experimental data with modeling techniques, we aim to provide insights into the predictive capabilities of these techniques in determining processing behaviors. The research highlights the superior fidelity of DSC in predicting the relative fraction and type of PE in a PP recyclate. FTIR is also identified as a high‐fidelity approach, albeit requiring application‐specific calibration. TGA, capillary, and oscillatory rheometry are recognized for their ability to distinguish between grades of recycled polyolefins but provide aggregate behaviors rather than detailed constituent information. 3D flow simulation of the cast film extrusion investigated the effect of the viscosity characterization method, non‐isothermal assumption, and process settings but could not fully replicate the observed variations in the cast film processing of two industrial polyolefins with similar melt flow rates and viscosity behaviors. This underscores the practical challenge of predicting processing issues prior to actual processing, necessitating reliance on reliable instrumentation suites and human expertise for diagnosing and remedying variations. Highlights: Two industrial recycled polypropylene materials having similar melt flow rates exhibit drastically different cast film processing behaviors.DSC and FTIR provide reasonable approaches for identifying constituent materials.Modeling of the melt viscosities characterized by capillary and parallel plate rheology suggests that viscosity variations relative to the power‐law behavior assumed in the coat hanger die design is a predominant driver of cast film instabilities. [ABSTRACT FROM AUTHOR]

Organic/inorganic nanocomposites uniquely combine the dual advantages of inorganic nanomaterials and organic polymers. However, poor compatibility between inorganic nanoparticles and polymer matrices always arises as a huge obstacle to be addressed while designing and preparing high performance organic/inorganic nanocomposites. In situ surface grafting of ethylene–vinyl acetate copolymer (EVA) onto nanosilica and partial cross-linking of EVA via dynamic Si–O–C bonds with nanosilica as the core were simultaneously achieved via the transesterification reactions between the inherent Si–OH groups on the surface of nanosilica and the ester groups in EVA. The reactions were conducted thorough a one-step, simple and scalable reactive blending approach. The cross-linking reaction of EVA was evidenced by torque curves, FT-IR spectra and gel fraction testing. Uniform dispersion of silica particles in EVA matrix was observed for resulting EVA/silica nanocomposites due to surface modification of silica. Consequently, tremendous enhancement in mechanical properties of resultant EVA/silica nanocomposites were detected. Compared to the original EVA, the tensile strengths and tensile modulus of the EVA/silica nanocomposites increased by 72.5% and 37.8%, respectively, while the elongation at breaks of the EVA/silica nanocomposites remained as high as that of the original EVA. Additionally, the dynamic nature of Si–O–C cross-linkages enabled partially cross-linked EVA/silica nanocomposites to demonstrate exceptional reprocess ability and recyclability. This was evidenced by the sustained mechanical properties of the EVA/silica nanocomposites, which were still maintained even after undergoing three rounds of reprocessing. [ABSTRACT FROM AUTHOR]

Developing plastics that fill the need of polyolefins yet are more easily recyclable is a critical need to address the plastic waste crisis. However, most efforts in this vein have focused on high‐density polyethylene (PE), while many different types of PE exist. To create broadly sustainable PE with modular properties, we present the synthesis, characterization, and demonstration of materials applications for chemically recyclable PE‐like multiblock polymers prepared from distinct hard and soft blocks using ruthenium‐catalyzed dehydrogenative polymerization. By altering the branching pattern within the soft blocks, a series of PE‐like multiblock polymers were synthesized with tunable glass transition temperatures (Tg) while maintaining consistent high melting temperatures (Tm). A clear U‐shape trend between Tg and mechanical properties was found, showcasing their potential as sustainable materials with tailored properties spanning commercial linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE). These materials offer adjustable adhesive strength to metal and demonstrate chemical recyclability and selective depolymerization in mixed plastic streams, promoting circularity and separation. [ABSTRACT FROM AUTHOR]

Laminated polymer composites are widely used in ballistic barriers where polyethylene can be applied. The mechanical properties of polymers can be improved with the addition of nanofillers. Therefore, this work evaluates the effect of the combination of montmorillonite Cloisite 30B (OMt) and graphene (Gr) on the dynamics compression properties obtained from a split‐Hopkinson pressure bar (SHPB) test for nanostructured maleinized high‐density polyethylene (HDPE). The nanofillers are incorporated into the polymeric matrix in its molten state, and their dispersion is evaluated through x‐ray diffraction and transmission electron microscopy analyses. Thermal analysis, including differential scanning calorimetry and thermogravimetric analysis are performed. Additionally, the viscoelastic behavior of the materials is studied from the results of storage and loss modulus obtained by dynamic‐mechanical analysis. Under the SHPB test conditions, it is possible to evaluate the material stress–strain curve, identifying its yield point, compressive strength, and deformations to calculate the elastic stiffness and toughness of the material. The nanocomposite with 3% OMt and 0.75% Gr (wt.%) shows the highest average compressive strength and toughness values. Furthermore, this sample shows similar Tpeak temperature, improved crystallinity index, storage, and loss modulus, with similar glass transition temperature compared to the HDPE sample. [ABSTRACT FROM AUTHOR]

The various steps in the mechanism of olefin polymerizations mediated by neutral rare‐earth metallocene complexes are discussed. The complexes are either trivalent hydride and alkyl rare‐earth compounds or divalent metallocenes that are activated by the monomer via an oxidation step. The stereospecific polymerizations of conjugated dienes based on the association of a cationic metallocene complex and an alkylaluminum and the polymerization mechanism based on monomer insertion into an aluminum‐carbon bond are also discussed. The exploitation of metallocene complexes for the copolymerization of olefins with conjugated dienes is the subject of a third part of this review. The synthesis of new elastomers called ethylene butadiene rubber (EBR) is highlighted. Finally, the use of rare‐earth metallocenes in macromolecular engineering is detailed. This includes the synthesis of functional polyolefins and block copolymers including thermoplastic elastomers. [ABSTRACT FROM AUTHOR]

This study compares the efficiency of commercially available sorbitol-based clarifying agent (NA) and varying amounts of long chain-branched polypropylene (LCBPP) acting as a specific α-nucleating agent for linear polypropylene (PP). The sorbitol-based clarifying agent, 1,3;2,4-bis(3,4-dimethyl benzylidene)sorbitol (Millad 3988), in concentration 0.2 wt%, and LCBPP in the concentration of 1, 2, 5 and 10 wt% were mixed into PP. The comparison of the effect of NA and long branches under isothermal conditions on the crystallization process, crystallinity and polymorphic composition was realized by differential scanning calorimetry and wide-angle X-ray scattering. The addition of long chain-branched polypropylene, even at the lowest concentration, performs better at higher crystallization temperatures and has a superior effect on the crystallization process, crystallization rate and overall crystallization than the addition of NA. [ABSTRACT FROM AUTHOR]

The influence of the concentration of various ethylene–vinyl alcohol (EVAlC) and ethylene–vinyl acetate copolymers on the properties of high-density and low-density polyethylenes is studied to develop compositions for utilization and recycling of polymer multilayer films containing EVAlCs as a barrier layer. It was found that EVAlCs have a lesser negative effect on the properties of mixtures based on high-density polyethylene. [ABSTRACT FROM AUTHOR]

In this study, a nanohybrid based on montmorillonite (oMMT2) was prepared through a two‐step method using Arquad MCB‐80 and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as intercalation agents. The nanohybrid exhibited a basal spacing of 31.5 Å, which contained approximately 12.3% of Arquad MCB‐80 and 31.6% of DOPO. Various amount of oMMT2 nanohybrid was incorporated into a flame‐retardant polyethylene system containing aluminum trihydroxide and red phosphorus with a constant total additive content of 20 wt%. The dispersibility of oMMT2 in the composite matrix was evaluated by energy dispersive x‐ray mapping and x‐ray diffraction analyses. At a content of 3 wt% in the nanocomposite, oMMT2 showed a highly exfoliated state, while at a 5% content, a partially exfoliated and intercalated state was observed. A synergistic flame‐retardant effect between the nanohybrid and the mixture of aluminum trihydroxide and red phosphorus was found. The nanocomposite loading 3 wt% oMMT2 demonstrated the best flame retardancy, achieving a V‐0 rating of the vertical burning test with a limiting oxygen index of 27.6%. Moreover, the addition of the low oMMT2 contents (≤3 wt%) improved the mechanical properties of the flame‐retardant composite. [ABSTRACT FROM AUTHOR]

This study provides key insights into the extrusion of a post‐industrial feedstock primarily composed of polypropylene (PP) and reveals its influence on the property profile of the recyclate. The objective of this study was to gain a fundamental understanding of complex process‐property relationships. Therefore, a two‐part experimental design was established. The first part aimed to analyze the feedstock variability by investigating key material properties of recyclates produced under constant processing conditions. The second part aimed to systematically evaluate the effect of the screw speed, filtration setup, and degassing setup on the properties of the recyclates. An industrial‐scale recycling extrusion line was used. The material evaluation included melt mass‐flow rate (MFR), ash content, oxidation induction temperature, tensile and impact properties, degassing performance, and residual volatile organic compounds (VOCs). Higher melt temperatures led to chain scission of the PP fraction, resulting in increased MFR and higher material stiffness. Additionally, a finer filtration positively contributed to the enhanced material stiffness. Furthermore, the mechanical properties were also influenced by the levels of inorganic fillers in the material composition of the feedstock. Finally, the filtration setup had a greater impact on degassing performance and residual VOC levels than the degassing setup and screw speed. [ABSTRACT FROM AUTHOR]

Polymers may suffer from sudden mechanical damages during long‐term use under various harsh operating environments. Rapid and real‐time self‐healing will extend their service life, which is particularly attractive in the context of circular economy. In this work, a lignin cluster polymerization strategy (LCPS) was designed to prepare a series of lignin functionalized polyolefin composites with excellent mechanical properties through nickel catalyzed copolymerization of ethylene and lignin cluster monomers. These composites can achieve rapid self‐healing within 30 seconds under a variety of extreme usage environments (underwater, seawater, extremely low temperatures as low as −60 °C, organic solvents, acid/alkali solvents, etc.), which is of great significance for real‐time self‐healing of sudden mechanical damage. More importantly, the dynamic cross‐linking network within these composites enable great re‐processability and amazing sealing performances. [ABSTRACT FROM AUTHOR]

Plastic waste, especially positively buoyant polymers known as polyolefins, are a major component of floating debris in the marine environment. While plastic colonisation by marine microbes is well documented from environmental samples, the succession of marine microbial community structure over longer time scales (> > 1 month) and across different types and shapes of plastic debris is less certain. We analysed 16S rRNA and 18S rRNA amplicon gene sequences from biofilms on polyolefin debris floating in a flow‐through seawater tank in Hawai'i to assess differences in microbial succession across the plastic types of polypropylene (PP) and both high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) made of different plastic shapes (rod, film and cube) under the same environmental conditions for 1 year. Regardless of type or shape, all plastic debris were dominated by the eukaryotic diatom Nitzschia, and only plastic type was significantly important for bacterial community structure over time (p = 0.005). PE plastics had higher differential abundance when compared to PP for 20 bacterial and eight eukaryotic taxa, including the known plastic degrading bacterial taxon Hyphomonas (p = 0.01). Results from our study provide empirical evidence that plastic type may be more important for bacterial than eukaryotic microbial community succession on polyolefin pollution under similar conditions. [ABSTRACT FROM AUTHOR]

To fulfil the European Green Deal targets and implement a circular economy, there is an urgent need to increase recycling rates of packaging materials. However, before recycled materials can be used in food contact applications, they must meet high safety standards. According to the European Food Safety Authority (EFSA), a worst-case scenario must be applied and unknown substances must be evaluated as being potentially genotoxic. The Ames test, which detects direct DNA-reactive effects, together with chromatographic analysis is very promising to complement risk assessment. This study aims to evaluate the effectiveness of functional barriers in ten different samples, including virgin and recycled LDPE foils. FT-IR analysis did not show major differences between virgin and recycled films. Light microscopy revealed differences in quality and an increased number of particles. GC-MS analysis detected and quantified 35 substances, including eight unknowns. Using a miniaturized version of the Ames test, four of ten samples tested positive in two individual migrates up to a dilution of 12.5%. All virgin LDPE materials tested negative; however, recycled material F showed an increased mutagenic activity, with an n-fold induction up to 28. Samples with functional barriers lowered migration and reduced mutagenicity. Nonetheless, further investigations are needed to identify possible sources of contamination. [ABSTRACT FROM AUTHOR]

Ultra‐high molecular weight polyethylene (UHMWPE) stands out as the preferred material across a wide spectrum of demanding applications, thanks to its remarkable mechanical, chemical and physical attributes. Nevertheless, processing UHMWPE can be an arduous and time‐consuming endeavor. Traditional melt‐processing techniques, commonly employed for polymers, prove impractical due to the exceedingly high viscosity of the melt that follows from the highly entangled macromolecular chains. Several methods are known to lower the entanglement density of UHMWPE, such as crystallization from a semidilute solution or direct polymerization, resulting in a less interconnected polymer structure. Unfortunately, even with low‐entangled UHMWPE, melt processing remains unviable because of the rapid re‐entanglement of polymer chains upon melting. However, these low‐entangled UHMWPE materials can still be effectively processed in the solid state, a technique employed in the production of high‐performance UHMWPE fibers and tapes, currently the only two feasible geometries. This research reports the development of a solid‐state extrusion method for nascent low‐entangled powder, centering on manipulating the surface energy of the interior wall materials within the extruder and die. Ordinary steel dies proved ineffective for solid‐state extrusion, as they generated excessive friction between the die and UHMWPE, resulting in a rapidly escalating extrusion pressure. However, utilizing dies constructed from temperature‐resistant polymers allowed for extrusion at a consistent pressure without the need for lubricating agents. We demonstrate the practicality of the developed solid‐state extrusion method by fabricating UHMWPE monofilaments and tubes, showcasing its potential in expanding the range of producible UHMWPE geometries. Additionally, a first evaluation of the influence of processing conditions and the entanglement density of the reactor powder used on extrudability, and the properties of the resulting components is presented. Highlights: A process for the solid‐state extrusion of UHMWPE is developed.UHMWPE processing with higher design flexibility than current industrial standards.UHMWPE processing with higher throughput than current industrial standards.Contrary to previous techniques no lubricating agent or co‐extrudate is used. [ABSTRACT FROM AUTHOR]

Blown films from ethylene-propylene random copolymers (C2C3-RACOs) are used in many packaging applications today, constituting a major fraction of both mono- and multilayer packaging film constructions. Combining high processing speed and output with good mechanical and optical performance, mostly high toughness and low haze, requires understanding the structure-property-processing relations. To improve said understanding for C2C3-RACO blown films, two commercial grades with a nearly identical C2 content of ~4.4 wt% and identical melt flow rate (MFR) but different nucleation were selected. These were tested in a processing study, varying melt temperature, blow-up ratio (BUR) and neck length. The film structure was analysed by wide angle X-ray scattering (WAXS) and atomic force microscopy (AFM), and the performance by standard mechanical and optical tests. Variation of film crystallinity was found to be in the range of 62 to 65%, much smaller than in earlier cast film studies on comparable polymers. The tensile modulus is the only performance parameter for which a general positive correlation to crystallinity can be found, blown films being about 50% stiffer than the softest cast films of a comparable polymer. Ductility and toughness are enhanced by higher orientation, resulting from higher BUR and/or higher neck length. For transparency and haze, low surface roughness is decisive at comparable crystallinity, which can be achieved by increasing melt temperature.

This scientific review delves into the innovative realm of polyolefins/light alkanes valorization through their catalytic dehydrogenation employing pincer-ligated iridium organometallic complexes. These widely studied catalysts exhibit outstanding properties, although the intrinsic characteristics of homogeneous catalysis (such as challenging product–catalyst separation, poor applicability to continuous-flow processes and low recyclability) limit their activity and industrial application, as well as their thermal stability. Through the immobilization of complexes on inorganic supports, these downsides have been bypassed, harnessing the true potential of these catalysts, affording more selective and stable catalysts in addition to facilitating their implementation in industrial processes. The findings described herein contribute to the advancement in the understanding of catalytic processes in hydrocarbon transformations, offering promising avenues for sustainable and selective production of valuable chemical intermediates from readily available feedstocks. [ABSTRACT FROM AUTHOR]

Poly(styrene‐b‐isobutylene‐b‐styrene) (SIBS) is a biomedical elastomer with excellent overall properties. However, the low surface energy and the surface hydrophobicity of SIBS have limited its application as a human implantable material. To improve its biocompatibility, in this work, hyaluronic acid (HA) was introduced onto the surface of SIBS. Firstly, glycidyl methacrylate (GMA) and HA were employed to prepare GMA‐modified HA (GMHA) via grafting reaction. Due to the introduction of carbon–carbon double bonds on the side chain of HA, the GMHA could be used for free radical polymerization between SIBS. The effects of UV illumination time, GMHA concentration, and initiator concentration on the grafting ratio were investigated. FTIR, 1H NMR, and XPS confirmed the successful grafting of HA onto SIBS. The experimental results showed that the surface modification method not only ensured that the excellent properties of the SIBS would not be destroyed but also improved its surface properties successfully. Besides, the MTT assay indicated that the GMHA‐modified SIBS was not bio‐toxic, so it could meet the need to expand its use in the biomedical fields. [ABSTRACT FROM AUTHOR]

This work describes the effect of functionalized silica, treated with organosilane (γ‐methacryloxypropyltrimethoxysilane), on the wettability loss of polypropylene (PP) film when exposed to surface oxidization treatment by atmospheric air plasma. The observed wettability loss results from the spontaneous process within the polymer matrix, which reduces surface energy, causing oxidized polymer molecules to move toward the bulk of the film. The effect of silica's functionalization on the initial wettability of oxidized PP film and its loss on storage time is measured by contact angle. Elemental analysis of the modified silica, employing acid catalytic processes, reveals the highest functionalization yield. Silicon nuclear magnetic resonance shows that the post‐condensation process negatively affects structures formed by the organosilane, eliminating three‐dimensional bonds and reverting it to its original and hydrolyzed state. The solvent extraction process and elemental analysis confirm that the concentration of organosilane in the chemically bonded layer, which was around 9 wt%, is not influenced by the post‐condensation treatment. Notably, silica functionalized with the highest concentration of organosilane has significantly improved initial wettability when oxidative treatment occurs within a shorter residence time (30 s), which achieved a contact angle of 53.8° against 59.1° for the film with untreated silica. However, the wettability loss rate of the materials remains unaffected by the presence of functionalized silica. [ABSTRACT FROM AUTHOR]

Understanding the percolation threshold is essential for determining the performance of particle‐reinforced polymer composites. Spray‐dried cellulose nanocrystals (SDCNC) of micrometer size reinforced homopolymer polypropylene (HPP) composites at 20, 30, 40, and 50 wt.% were prepared to investigate the percolation threshold of SDCNC particles in HPP. The effect of a compatibilizer (maleic anhydride polypropylene (MAPP)) at 3, 5, and 7 wt.%, on the SDCNC percolation networks and composites performance were also studied. The results indicated that SDCNC particle percolation networks in HPP were established between 30 and40 wt.%. For composites without MAPP, the impact strength significantly increased by up to 23% below the percolation threshold and declined beyond it. The peak crystallization temperature of HPP was steadily increased until 30 wt.% SDCNC particles were added due to the SDCNC saturated nucleation function at the threshold. Introducing MAPP significantly improved tensile strength (58%), tensile strain (61%), flexural strength (45%), and impact strength (91%) compared with the corresponding composites without MAPP, attributed to the enhanced interfacial adhesion between the SDCNC particles and HPP. Water absorption results indicated that adding MAPP changed the SDCNC particle distribution networks within the matrix above the percolation threshold but did not change it below the threshold. [ABSTRACT FROM AUTHOR]

Isotactic polythioesters (PTEs) that are thioester analogs to natural polyhydroxyalkanoates (PHAs) have attracted growing attention due to their distinct properties. However, the development of chemically synthetic methods for preparing isotactic PTEs has long been an intricate endeavour. Herein, we report the successful synthesis of perfectly isotactic PTEs via stereocontrolled ring‐opening polymerization. This binaphthalene‐salen aluminium (SalBinam‐Al) catalyst promoted a robust polymerization of rac‐α‐substituted‐β‐propiothiolactones (rac‐BTL and rac‐PTL) with highly kinetic resolution, affording perfectly isotactic P(BTL) and P(PTL) with Mn up to 276 kDa. Impressively, the isotactic P(BTL) formed a supramolecular stereocomplex with improved thermal property (Tm=204 °C). Ultimately, this kinetic resolution polymerization enabled the facile isolation of enantiopure (S)‐BTL, which could efficiently convert to an important pharmaceutical building block (S)‐2‐benzyl‐3‐mercapto‐propanoic acid. Isotactic P(PTL) served as a tough and ductile material comparable to the commercialized polyolefins. This synthetic system allowed to access of isotactic PTEs, establishing a powerful platform for the discovery of sustainable plastics. [ABSTRACT FROM AUTHOR]

Although anion‐exchange membranes (AEMs) are commonly used in fuel cells and water electrolyzers, their widespread commercialization is hindered by problems such as low anion conductivity and durability. Moreover, the development of high‐performance AEMs remains complex and time consuming. Here, we address these challenges by proposing an innovative approach for the efficient design and screening of AEM polymers using unsupervised machine learning. Our model, which combines principal component analysis with uniform manifold approximation and projection, generates an intuitive map that clusters AEM polymers based on structural similarities without any predefined knowledge regarding anion conductivity or other experimentally derived variables. As a powerful navigation tool, this map provides insights into promising main‐chain structures, such as poly(arylene alkylene)s with consistently high conductivity and polyolefins with exceptional performance depending on the substituent. Furthermore, assisted by key molecular descriptors, inverse analysis with this model allows targeted design and property prediction before synthesis, which will significantly accelerate the discovery of novel AEM polymers. This work represents a paradigm shift not only in AEM research but also generally in materials research, moving from black‐box predictions toward interpretable guidelines that foster collaboration between researchers and machine learning for efficient and informed material development. [ABSTRACT FROM AUTHOR]

In order to develop smart concrete with afterglow emission, epoxy resin (EPX) was immobilized with nanoparticles of alkaline earth aluminate (NAEA) as a photoluminescent agent and electrospun polypropylene nanofibers (EPN) as a reinforcement agent. Scanning electron microscope images of EPN displayed diameters of 70–90 nm, whereas transmission electron microscopic images showed that NAEA has diameters of 3–9 nm. To create a transparent sheet that glows in the dark, NAEA were physically immobilized in EPN@EPX composite. CIE Lab and photoluminescence spectrum studies demonstrated that EPN@EPX bars turned greenish upon exposure to ultraviolet (UV) rays and greenish-yellow in a darkened box. The luminous EPN@EPX morphologies and chemical compositions were analyzed using various analytical methods. The resistance to scratching of EPN@EPX bars was monitored to considerably increase with increasing NAEA concentration. The photoluminescence spectrum demonstrated two emission peaks at 437 and 518 nm. Photoluminescent EPN@EPX hybrids with low NAEA content have shown rapid photochromism reversibility. On the contrary, NAEA-rich EPN@EPX bars displayed slow reversibility, glowing in the dark. Superhydrophobicity and UV blockage were found to be significantly improved in the luminescent colorless EPN@EPX hybrids. [ABSTRACT FROM AUTHOR]