Search

Polymer blend compatibilization is an attractive solution for mechanical recycling of mixed plastic waste because it can result in tough blends. In this work, hydroxy-telechelic polyethylene (HOPEOH) reactive additives were used to compatibilize blends of polyethylene terephthalate (PET) and linear low-density polyethylene (LLDPE). HOPEOH additives were synthesized with molar masses of 1-20 kg/mol by ring-opening metathesis polymerization of cyclooctene followed by catalytic hydrogenation. Melt-compounded blends containing 0.5 wt % HOPEOH displayed reduced dispersed phase LLDPE particle sizes with ductilities comparable to virgin PET and almost seven times greater than neat blends, regardless of additive molar mass. In contrast, analogous blends containing monohydroxy PE additives of comparable molar masses did not result in compatibilization even at 2 wt % loading. The results strongly suggest that both hydroxy ends of HOPEOH undergo transesterification reactions during melt mixing with PET to form predominantly PET-PE-PET triblock copolymers at the interface of the dispersed and matrix phases. We hypothesize that the triblock copolymer compatibilizers localized at the interface form trapped entanglements of the PE midblocks with nearby LLDPE homopolymer chains by a hook-and-clasp mechanism. Finally, HOPEOH compounds were able to efficiently compatibilize blends derived solely from postconsumer PET and PE bottles and film, suggesting their industrial applicability.

Polyolefins might become inexpensive alternatives to the existing membranes based on polyethersulfone. Here, we disclose the production of retortable, well-defined polypropylene (PP)-based nanoporous films derived from amphiphilic graft copolymer precursors. The graft copolymers, containing a polypropylene backbone and polyester grafts, were obtained by grafting lactones, specifically delta-valerolactone and epsilon- caprolactone, from well-defined randomly functionalized poly(propylene-co-10-undecen-1-ol) as a macroinitiator. Depending on the composition, the graft copolymers self-assemble into droplet, cylindrical, lamellar, or interconnected two-phase morphologies. Functional mesoporous iPP-based films were fabricated by the selective degradation of the polyester blocks of the copolymers. Their structure and morphology were studied using atomic force microscopy (AFM), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and solid-state NMR, while the mesoporosity was assessed by nitrogen sorption experiments. The pore size of the films is strongly influenced not only by the volume fraction of the copolymer blocks but unexpectedly also by the topology (i.e., number of grafts) of the graft copolymer, as was confirmed by computational modeling studies using the dynamic density functional theory (DDFT) engine within the Culgi software. This work provides a conclusive answer on how the morphology of iPP-based graft copolymers is tuned by the copolymer composition and the amount and length of the grafted polyester blocks. Filtration tests and flux determination demonstrated that such structurally well-defined mesoporous products could be considered for the development of ultrafiltration membranes while the chemical resistance and sterilization tests revealed their robust performance and suitability for water purification applications.

Researchers have long sought to predict the mechanical behavior of polyethylene from its microstructure. In particular, the yield strength and yield kinetics have been reported to be dependent on crystallinity and crystal thickness, but the relative importance of these two microstructural attributes has not been shown. In the present work, a series of microstructures was obtained through a combination of controlled quench rates from the melt and inclusion of various amounts of hexene comonomer. The yield strength for a wide range of strain-rates was linearly dependent on the crystallinity, and independent of crystal thickness (chain stem length), both measured by Raman spectroscopy. Similarly, yield kinetics described by a Ree-Eyring two-process stress activated model showed linear dependence on crystallinity and no dependence on crystal thickness. The results of the present work call into question models of yield kinetics dependent on screw dislocation nucleation, which depend on crystal thickness.

Introducing the reverse micelle formation during polymerization, and thus avoiding the catalyst support, aggregated single crystals of ultra-high molecular weight isotactic polypropylene having spherical morphology are obtained. The ease in flowability of the spherical nascent morphology, having a low-entangled state in the non-crystalline region of the single crystals in the semi-crystalline polymer, allows the sintering of the nascent polymer in the solid state without melting. Thus maintains a low-entangled state, and facilitates the translation of macroscopic forces to macromolecular length scale, without melting, leading to the formation of uniaxially drawn objects having unprecedented properties that can be used in the development of one component, high-performance, easy-to-recycle composites. Thus having the potential of replacing difficult-to-recycle hybrid composites.

The accelerated aging of polyethylene terephthalate (PET) multifilament yarns containing nano or microparticles of titanium dioxide (TiO2), silicon carbide (SiC), or fluorite (CaF2) at a maximum percentage of 2% has been studied. For this, the yarn samples were introduced into a climatic chamber at 50 °C, 50% relative humidity, and an ultraviolet A (UVA) irradiance of 1.4 W/m2. They were then removed from the chamber after periods of between 21 and 170 days of exposure. Subsequently, the variation in weight average molecular weight, number molecular weight, and polydispersity was evaluated by gel permeation chromatography (GPC), the surface appearance was evaluated using scanning electron microscopy (SEM), the thermal properties were evaluated using differential scanning calorimetry (DSC), and the mechanical properties were evaluated using dynamometry. The results showed that, at the test conditions, there was degradation in all of the exposed substrates, possibly due to the excision of the chains that make up the polymeric matrix, which resulted in the variation in the mechanical and thermal properties depending on the type and size of the particle used. This study provides insight into the evolution of the properties of PET-based nano- and microcomposites and might be helpful when selecting materials for specific applications, which is of great interest from an industrial point of view The authors gratefully acknowledge the financial support for this research from the Ministry of Science and Innovation of Spain (Project MAT2010-20324-CO2-01) and the National Secretary of the Higher Education Science Technology and Innovation of Ecuador (SENESCYT) for Fellowship No. CZ02-000926-2018

Background: Mesio–occluso–distal (MOD) cavity preparations are often fragile due to the amount of tooth and carious structure removed. MOD cavities can often fracture if left unsupported. Aim: The study investigated the maximum fracture load of mesi–occluso–distal cavities restored using direct composite resin restorations with various reinforcement techniques. Method: Seventy-two freshly extracted, intact human posterior teeth were disinfected, checked, and prepared according to predetermined standards for mesio–occluso–distal cavity design (MOD). The teeth were assigned randomly into six groups. The first group was the control group restored conventionally with a nanohybrid composite resin (Group I). The other five groups were restored with a nanohybrid composite resin reinforced with different techniques: the ACTIVA BioACTIVE-Restorative and -Liner as a dentin substitute and layered with a nanohybrid composite (Group II); the everX Posterior composite resin layered with a nanohybrid composite (Group III); polyethylene fibers called “Ribbond” placed on both axial walls and the floor of the cavity, and layered with a nanohybrid composite (Group IV); polyethylene fibers placed on both axial walls and the floor of the cavity, and layered with the ACTIVA BioACTIVE-Restorative and -Liner as a dentin substitute and nanohybrid composite (Group V); and polyethylene fibers placed on both axial walls and the floor of the cavity and layered with the everX posterior composite resin and nanohybrid composite (Group VI). All teeth were subjected to thermocycling to simulate the oral environment. The maximum load was measured using a universal testing machine. Results: The highest maximum load was exhibited by Group III with the everX posterior composite resin, followed by Group IV, Group VI, Group I, Group II, and Group V. A statistically significant difference was demonstrated between groups (p = 0.0023). When adjusting for multiple comparisons, there were statistical differences specific to comparisons between Group III versus I, Group III versus II, Group IV versus II, and Group V versus III. Conclusions: Within the limitations of the current study, it can be concluded that a higher maximum load resistance can be achieved (statistically significant) when reinforcing nanohybrid composite resin MOD restorations with everX Posterior.

Here we report on the influence of an aliphatic oxalamide-based nucleating agent (OXA3,6) on the viscoelastic and mechanical properties of isotactic polypropylene (iPP) blended with ultrahigh molecular weight iPP (UHMWiPP). The linear viscoelastic properties are investigated by using a plate-plate rheometer; the presence of only 0.5 wt % of OXA3,6 in the iPP-UHMWiPP blends results in a reduction of the complex viscosity in the entire frequency domain examined. This observation holds irrespective of the UHMWiPP weight fraction, up to 25 wt %. The viscosity suppression is attributed to an acceleration of the reorientation times of the chains, especially the longer ones, due to partial alignment of their molecular segments. Furthermore, SAXS measurements on cooled, injection molded samples hint that OXA3,6-containing samples display enhanced alignment under processing conditions (injection molding). Compared to samples without OXA, an increase in the SAXS intensity along the equator is observed in the OXA3,6 samples, implying an enhanced ability of shish-kebab formation. Such a morphological development results in higher yield stress while maintaining the elastic behavior.

Low density polyethylene (LDPE) and high density polyethylene (HDPE) are the principal plastics present in solid plastic waste and are found out as the main components of microplastics in marine and terrestrial environments. Currently, efforts have been made to develop new and effective methods to ensure the identification and separation of plastics in waste, ensuring the necessary purity to obtain quality and economically competitive recycled products. In this contribution, we investigated the usage of Fourier-Transform Infrared Spectroscopy in attenuated total reflection mode (ATR-FTIR) combined with Principal Component Analysis (PCA), Linear Partial Least Squares Regression by Intervals (iPLS-R) and Competitive Adaptive Weighted Sampling (CARS/PLS-R) as chemometric methods to classify and determine the compositional fraction of the pristine and recycled mixtures of HDPE and LDPE from plastic waste in São Paulo, Brazil. The 3D PCA plots do not make it possible to classify the different polyethylenes and their polymer blends using the three Principal Components (PC), except for the 2D PCA diagram using PC1 and PC3. The iPLS-R presents the best predictive ability than CARS/PLS-R to determine the LDPE content in HDPE/LDPE recycled blends. However, the presence of different contaminants (in 5 wt%), such as silicon dioxide (SiO2), calcium carbonate (CaCO3), recycled polypropylene (PP), and recycled poly(ethylene terephthalate) (PET), reduces the potential usage of the iPLS-R models as identification tools for LDPE and HDPE sorting in industrial recycling processes.

Graphical Abstract In view of the intense interest in applications of silver nanoparticles in products for the medical field and in food preservation packaging due to their antimicrobial properties, the ecotoxicology of silver nanocomposites was evaluated in films. Test with the sea urchin Echinometra lucunter, to evaluate embryonic development and contamination by the action of silver and titanium nanoparticles in polyethylene nanocomposite films presents new results. The silver nanoparticle’s stability in polymeric materials can be enhanced by adding carriers, such as titanium dioxide and montmorillonite clay (MMT) without to producing one unfriendly material. For this research, low-density polyethylene (LDPE)/linear low-density polyethylene (LLDPE) were used processed in a twin-screw extruder, followed by gamma irradiation with 25 kGy and characterized by ecotoxicology assays, field emission scanning electron microscopy (FESEM), scanning electron microscopy and energy dispersive spectroscopy (SEM–EDX), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), Raman spectroscopy (SERS) and mechanical properties. The antibacterial properties of the LDPE films were investigated against Escherichia coli and Staphylococcus aureus. The gamma irradiation had an important effect in the synthesis of silver nanoparticles resulting in bactericidal activity and the death of 100% of the tested bacteria. The evaluation of the environment was considered with the ecotoxicological investigation carried out. The results indicated that the polymeric films with silver nanoparticles and TiO2 do not contaminate the environment and neither interfere with the larval development of Echinometra lucunter. The obtained materials can be used in various applications with antimicrobial properties.

Herein, the synthesis of polyethylene via an innovative post-polymerization modification (PPM) approach is reported. For this, a block copolymer of poly[

In the present study, we investigated the possibility of value-added recycling of ultrafine ground tire rubber (uGTR) produced from water jet milling, with an average particle size of a few tens of microns. Our goal was to compare the properties of blends with different uGTR and conventional fine ground tire rubber (fGTR) contents prepared by blending with low-density polyethylene (LDPE). We also aimed to explore the property changes caused by the larger specific surface area due to the size effect. Samples were prepared with a hydraulic press after internal mixing. In the case of ground tire rubber (GTR) filled mixtures, the tensile properties showed rubber-like characteristics: with a significant decrease in modulus, elongation at break remained high, and tensile strength slightly decreased. The fracture surfaces of the samples were analyzed by scanning electron microscopy (SEM), wherein the case of materials made with uGTR showed better adhesion between the phases. In order to investigate the interfacial adhesion between the GTR and LDPE, we performed dynamic mechanical thermal analysis (DMTA). The glass transition peak of the uGTR shifted to a higher temperature and the storage modulus was higher than in the case of samples containing fGTR. Finally, we determined the Shore D hardness of the materials, which decreased with increasing GTR content, but hardness was greater in the case of uGTR samples. The better mechanical properties of blends containing uGTR were explained by better interfacial adhesion between the two phases due to the significantly higher specific surface area compared to fGTR.

At present, there is a vital need for river water purification by developing new approaches to eliminate bacterial biofilms, textile dyes, and Low-Density Polyethylene (LDPE) plastics that pose severe threats to human and environmental health. The current work put forward the construction of an eco-friendly green strategy to synthesize zinc oxide nanoparticles (ZnO NPs) using areca nut (Areca catechu) extract and their application to tackle the challenges in water purification. Prepared biogenic NPs were characterized by X-ray diffraction analysis (XRD), Fourier Transform Infra-Red (FT-IR), Energy Diffraction Spectroscopy (EDS), Scanning Electronic Microscopy (SEM), Transmission Electron Microscopy (TEM) analysis, confirmed the spherical shape in 20 nm and UV–vis spectroscopy. The characteristic absorption band exhibited at 326 nm confirmed the formation of ZnO NPs using UV–vis spectroscopy. Among all the tested bacterial pathogens, the E. coli at 50 µg/mL concentration showed the highest inhibition of biofilm activity, followed by the highest growth curve, cellular leakage, and potassium ion efflux. The ZnO NPs observed with photo-degradation of Rhodamine-B (Rh-B), Methylene Blue (MB), and Nigrosine dyes under sunlight irradiation at different time intervals. Finally, the photocatalytic activity of LDPE-ZnO NPs nanocomposite film showed the highest degradation under solar light irradiation were confirmed through photo-induced weight loss, SEM, FTIR, and MALDI-TOF analysis. This study demonstrates ZnO NPs exhibit efficacy against biofilm formation, degradation of photocatalytic textile dyes, and low-density LDPE film under solar light irradiation, which can be a step forward in water purification.

Bio-derived polyethylene furanoate (PEF) has recently gained attention as a sustainable alternative to polyethylene terephthalate (PET), amidst environmental concerns over fossil fuel depletion. He...

Waste plastics recycling and oil/organics remediation are environmental issues of global concern. In this work, a protectant was introduced, for the first time, to make highly efficient catalysts for pyrolysis of waste plastics into carbon nanotubes (CNTs) with high yield. By using waste polyethylene, Co(NO3)2 and oleylamine respectively as carbon source, catalyst precursor and protectant, a yield as high as 59.0% was achieved. The CNTs exhibited a high adsorption capacity for methylene blue (up to 107.1 mg/g). Furthermore, by combining the CNTs with graphene oxide, a graphene-CNT aerogel with a low density of 8.2 mg/cm3 and high porosity of 96.0% was successfully prepared. It showed excellent hydrophobicity and mechanical stability, as well as high adsorption capacity of 289–410 g/g oil/organic solvent, which was much higher than most of these achieved by carbon-based three-dimensional materials reported previously, making the as-prepared aerogel a very promising adsorbent for oil/water separation.

We measured phytoplankton primary production and heterotrophic bacterial activities on microplastics and seawater in the Northwestern Mediterranean Sea during two 3-month spring periods over 2 consecutive years. Microorganisms growing on a 5 mm diameter low density polyethylene films (LDPE; 200 μm thick) faced two contrasting conditions depending on the year. Spring 2018 was characterized by consistent nutrient inputs and bloom development. In spring 2019, nutrient inputs and bloom were low. For the first time, we observed a clear coupling between primary production and heterotrophic prokaryote production on microplastics during both years, but with different intensity between years that reflected the crucial role of the trophic environmental conditions (nutrient supply) in shaping microbial activities on plastics. We found that high primary production on plastics could support the whole (net autotrophy) or the majority of the bacterial carbon demand needed for heterotrophic activities, supplemented by other carbon sources if surrounding waters are highly productive. We propose that microbial activity on plastics influences the microbial community in the surrounding seawater, especially when the environmental conditions are less favorable. An illustrative image of the role of plastics in the environment could be that of an inverter in an electrical circuit that mitigates both positive and negative variations. Our results highlight the potential role of the plastisphere in shaping biogeochemical cycles in the context of increasing amounts of plastic particles in the marine environment.

Samples of polyethylene with extended-chain crystal morphology, obtained by crystallization under high pressure, were subjected to uniaxial compression to various strains. Accompanying structural changes were analyzed using scanning electron microscopy. At the true strain of e = 0.2–0.3 the microbuckling instability was observed in longitudinally loaded lamellae, resulting in the formation of angular kinks. This induced a rapid reorientation of the lamellae, facilitating their further deformation by crystallographic slip. Microbuckling instability was found to occur earlier than in samples with folded-chain crystal morphology (e = 0.3–0.4) due to a smaller ratio of the amorphous to crystalline layer thickness. SEM observations demonstrated that the microbuckling instability begins with small undulation in long lamellae. Sharp angular lamellar kinks develop from the initial undulation through intense plastic deformation by crystallographic slip along the chain direction. The same slip system was found to operate throughout the kink, including the tip region as well as both limbs. In contrast to thin folded-chain lamellae that often undergo fragmentation during deformation, the thick extended-chain lamellae deform stably by chain slip and retain their continuity up to high strains, e > 1.6. This stability of deformation is related to the large thickness of extended-chain lamellae.

A significant portion of the global plastics market encompasses the production of polyolefin materials and especially polypropylene (PP) and polyethylene (PE), as commodity polymers with a wide range of applications. However, the increase in the generation of unsustainable plastic waste requires a close technological look-up to address this challenge adequately. In this context, mechanical recycling is part of the strategies expected to contribute to the solution. Nevertheless, the melt blending process presents a challenge due to the immiscibility between PP and PE. Therefore, compatibilization strategies are meant to solve the problem effectively. In this paper, we employ a commercial ethylene-ran-methyl acrylate random copolymer as a compatibilizer for PP/PE blends. With the addition of the compatibilizer, it was possible to obtain a 44% reduction in PE domain size, while ductility increased by around similar to 40% with respect to uncompatibilized blends. Interesting results were obtained concerning the crystallization behavior of the blends. The overall isothermal crystallization kinetics of the different blend components was studied, and a synergistic nucleation effect of the PP and the compatibilizer toward the PE phase was found. For the first time, the effect of the compatibilizer on the surface nucleation of PE in a self-nucleated PP matrix phase is reported. An enhancement in the crystallization rate of PE was found when the self-nucleation protocol was applied to the polypropylene matrix phase for neat and compatibilized blends. The nucleation efficiency was in the range of 120-124%, indicating a supernucleation behavior. The induced crystallization at the interface by the self-nucleated polypropylene is the reason for such high nucleation efficiencies. Surprisingly, a higher amount of compatibilizer decreases the overall crystallization rate of PE droplets. The compatibilizer segregates at the interface between both polymers, reducing the surface nucleation of the PE droplets on the PP matrix phase. The results presented in this paper lead the way toward improving the use of post-consumer recycled materials. All of the sources of funding for the work described in this publication are acknowledged below: This work has received funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No 860221 under the name of the REPOL project.

High-temperature thermal gradient interaction chromatography (HT-TGIC) can be used to measure the chemical composition distribution of ethylene/α-olefin copolymers using a column packed with porous...

We describe an in situ facile synthetic approach to prepare carbon quantum dot (CQD) fluorescent markers (FMs) for polyethylene (PE) in the presence of agglomerated silica nanoparticles (SiO2 NPs) under mild reaction conditions. First SiO2 NPs, prepared by the Stöber method, were dispersed in toluene. This dispersion was added to a PE solution in toluene. After heating (either in air or under Ar) a fluorescent mixture was obtained. After drying, PE films were obtained by compression molding, which showed strong blue fluorescence, attributed to CQDs. SiO2 NPs loading values varied between 0.5 and 4 wt %. Subsequent to isolation, the fluorescent CQDs were characterized by TEM, UV-vis, and fluorescence spectroscopy. TEM imaging unveiled a lattice spacing value of 0.21 nm of the isolated fluorescent particles which is typical for (100) graphite plane lattice spacing in CQDs. UV spectroscopy and fluorescence measurements show characteristic absorption and excitation spectra for the aromatic core and oxidized surface defects typically observed for CQDs. The emission maximum for PE/CQD samples increased from 394 to 408 nm when the reaction temperature was decreased from 110 to 90 °C, which is attributed to increasing oxygen content in the reaction mixture upon decreasing the reaction temperature. When the reaction was performed under Ar, the PE/CQD samples emitted in the ultraviolet region (286 nm). Finally, we demonstrated that PE samples marked with CQDs can be easily visually identified upon irradiating with 367 nm light. Thus, the marked PE can be used, for example, as a labeling ingredient in master batches for component identification and in recycling.

We examined the general rheological characteristics of short-chain branched (SCB) ring polyethylene (PE) melts using atomistic nonequilibrium molecular dynamics (NEMD) simulations under shear in a ...

Olefin polymerization reactions mediated by diamido-supported titanium complexes are a part of post-metallocene studies. In the present work, dichlorido{di(3-methylindol-2-yl)phenylmethane}titanium (1) and dichlorido{di(3-methylindol-2-yl)-2-methoxyphenylmethane}titanium (2) were applied for ethylene polymerization. The results showed that the 2/MMAO catalyst system, where MMAO is a modified methylaluminoxane, exhibits ethylene polymerization activity up to 2494 (kg of polyethylene)/(mol of Ti)·h·atm. This activity is comparable to the highest known activity in catalyst systems based on diamido-supported titanium complexes. The 2/MMAO system was also active for propylene polymerization (344 (kg of polypropylene)/(mol of Ti)·h·atm) to furnish atactic polypropylene. Bis(indolyl)-coordinated titanium dichlorido complexes were applied for ethylene polymerization. The results showed that [{bis(indolyl)}TiCl2]2 activated by modified methyl aluminoxane (MMAO) exhibited ethylene polymerization activity up to 2494 (kg of polyethylene)/(mol of Ti)·h·atm. This activity is comparable to the highest known activity in catalyst systems based on diamido-supported titanium complexes. The [{bis(indolyl)}TiCl2]2/MMAO catalyst system was also active for propylene polymerization (344 (kg of polypropylene)/(mol of Ti)·h·atm) to furnish atactic polypropylene.

The pressure-temperature (P-T) phase diagram for polyethylene (PE) was calculated based on the empirical Gibbs free energy (G) equation of state, GFE-Eos, for the crystalline PE (crys-PE) and the a...

The impact of bacterial diseases and the development of effective antimicrobial agents have drawn much consideration as a main healthcare challenge. The effects of montmorillonite/silver nanocomposites (MMT/Ag NCs) as a nanofiller on mechanical and thermal properties of linear low-density polyethylene/ethylene–vinyl acetate copolymers blend (LLDPE/EVA) had been investigated. The antimicrobial potential of the synthesized samples had been studied. The developed LLDPE/EVA/MMT/Ag nanocomposites films (NCFs) had been characterized by UV–Vis. spectroscopy, FTIR and XRD analysis. The mechanical, and thermal properties of LLDPE/EVA/MMT/Ag NCFs had been investigated. The results showed that incorporating the MMT/Ag NCs at lower phr (part per hundred resins) content resulted in both improvement in the mechanical properties and the thermal stability. The antimicrobial results demonstrated that LLDPE/EVA blend with 5 phr MMT/Ag NCs possesses the most powerful impact on the tested microbes. The SEM analysis of the treated cells showed, noticeable morphological abnormalities (the complete lysis of the outer surface followed by deformations of cells). Accordingly, the synthesized nanocomposites open the area of interest for possible application in a broad range of purposes like environmental and biomedical applications.

In this paper, firstly, polypyrrole was prepared by in situ polymerization using pyrrole as the monomer, hexahydrate ferric chloride as the oxidizer and dopant, and polyethylene geotextile as the substrate to prepare a polypyrrole/polyethylene short filament geotextile composite; secondly, the electromagnetic microwave absorption property and shielding property of the polypyrrole/polyethylene short filament geotextile composite were investigated; finally, the chemical structure of the polypyrrole/polyethylene short filament geotextile composite was characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman test methods. The results show that the reflection loss value is up to the minimum value of –17.53 dB in the frequency range of 0–3 GHz and the best absorbing performance is obtained at the frequency of 1.12 GHz. In the frequency range of 0.95–1.25 GHz, the reflection loss value is less than –10 dB, and the electromagnetic wave is effectively absorbed. The shielding effectiveness value is up to the maximum value of 16.07 dB at the frequency of 1.19 GHz, that is, the shielding ability becomes strongest at the frequency of 1.19 GHz; otherwise, the shielding effectiveness is higher than 14 dB in the frequency range of 0.17–3.0 GHz. The FTIR, Raman, XRD, and DSC tests result show that polypyrrole has been successfully loaded on the polyethylene geotextile, improving the crystallinity and thermal stability property of the composite.

Herein, we report on a new and innovative post-polymerization modification procedure for the ethylene-free synthesis of polyethylene copolymers and block copolymers. Poly[N-(acryloyloxy)phthalimide...

In this study, three PEG-maleated rosin polyesters were produced by reacting between maleated rosin and PEG with different molecular weights and served as surfactants. The surface characteristics of these PEG-maleated rosin polyesters were detected. The conformational transition and adsorption characteristics of these polyesters were analyzed with the reorientation theory on the water–air surface. The surfactant mole fraction at the water–air surface increased as surfactant concentration increased, while the solvent mole fraction was decreased. The amount of surfactant on the water–air surface at state 1 with a maximal molar area appeared one unimodal in distribution and that at state 2 occupying a minimal molar area appeared a sigmoid distribution with П growth. The calculated adsorption free energy from CMC value is lower than calculated micellization energy obtained from molecular area at state 2 indicates the polyethylene glycol-maleated rosin polyesters firstly spread on the water–air surface and then aggregated into micelles. The results lay a foundation for better understand the adsorption and self-assembly processes. The adsorption characteristics and conformational transition of three PEG-maleated rosin polyesters were investigated. Paper title: Adsorption Characteristics and Conformational Transition of Polyethylene Glycol-maleated Rosin Polyesters on the Water–Air Surface

In this study, the effects of filler amounts were studied on the mechanical and thermal properties of high-density polyethylene (HDPE), polystyrene (PS) and polyoxymethylene (POM) polymers reinforced with short rape fibers. HDPE-rape, POM-rape and PS-rape fiber composite materials were prepared with different fiber contents and their tensile, flexural, Izod impact and TGA/DTA properties were examined. When tensile and Izod impact properties were compared, it was observed that an increase in the amount of filling in HDPE-based composites did not cause any significant changes in these peoperties, while they were decreased for POM- and PS-based composites. On the contrary to tensile and impact strengths, when the three-point flexural properties were examined, it was observed that the strength values of all these materials increased with increasing the amount of fillers. However, a pronounced increase was observed in the three-point flexural strength of the HDPE-based composite materials. The flexural strength of 30 wt% rape-reinforced HDPE composite was found to be twice that of the pure HDPE. The results of TGA and DTA analyses revealed that the reinforcement element started to burn before the matrix material and therefore burning was delayed in these thermoplastics. As a result, the mechanical properties of HDPE composite materials improved with rape reinforcement. In this way, by using approximately 30 wt% natural filling material in a polymeric matrix, an environmentally friendly material, as well as, significant advantages in cost can be obtained.

Samples of LDPE (low-density polyethylene) and LDPE-PANSA (low-density polyethylene -4-Amino-3-hydroxy- 1-naphthalenesulfonic acid) copolymer with Ag0.5�Ni0.5�Fe2O4 powder (as a filler) composites were developed. Following the preliminary characterizations on the thermooxidability (by thermal analysis techniques), the dielectric behavior (by dielectric spectroscopy technique), the mechanical behavior, etc. it was found that the developed materials do not show significant changes after 240 h exposure to 150 mW / m2 UV. The addition of 3wt% PANSA in LDPE has the effect of increasing the mechanical performance of polymer composites with Ag0.5�Ni0.5�Fe2O4 filler. The addition of 15 wt% ferritic powder leads to significant increases in dielectric losses (by about 100% in the case of pure LDPE and about 185% of the LDPE copolymer with 3 wt% PANSA) and to the increase of the real component of the relative permittivity (by about 34.4 % in LPDE, respectively about 36.4% in LPDE copolymer / 3% wt PANSA). Dielectric behavior of the investigated materials indicates that the effect of Ag0.5�Ni0.5�Fe2O4 powder in LDPE and of copolimer LDPE with 3 wt% PANSA consists in the increasing of the shielding efficiency of electromagnetic waves - the maximum effect being recorded in the case of the composite material with the content: LDPE 84.5 wt%, 2.5 wt% / PANSA and 13% wt% Ag0.5�Ni0.5�Fe2O4.

In this study, the composite materials based on high density polyethylene (HDPE) and yellow phosphorus slag (YPS, by-product of yellow phosphorus production) were prepared using melt blending metho...

Biodegradable compositions based on low-density polyethylene and polylactide containing arabinogalactan are obtained. Their mechanical properties are studied. It is shown that the development of absorbents based on arabinogalactan is complicated by specific features of the structure of its macromolecules, and possible methods of for overcoming them are considered.

Popularly, the application of biodegradable polymer film can resolve polyethylene (PE) film residual “white pollution” but it is unclear when the degradable film begins to degrade in different regions. To solve these issues, a total of 32 papers on the subject of the relative film coverage durability (RFCD) on positive covering effect from papers published before July 2019 were selected and analyzed by meta-analysis. The results showed that the tobacco relative yield (RY), relative profit (RP), and relative fine and medium (RFM) ratio improved by 11.2%, 12.9%, and 12%, respectively, under fully covered compared with the uncovered tobacco in the whole growth period. The RY0.33 and RP0.33 of removed PE treatments significantly improved by 4.3% and 4.0%, respectively, compared with the fully covered treatments. The RFM did not show significance with the fully covered treatments. The RY0.33 was the highest in the low altitude (less than 1,000 m) region; however, the RY under the fully covered treatments was the greatest in the high altitude (more than 1,000 m) region. Random effect analysis showed that the model between RFCD and RY was RY = 1 + 0.275 × (1 − RFCD) – 0.357 × (1 − RFCD)2, and the RYmax(1.053) was reached with RFCD = 0.62 (removed PE after covering for 80 days) in the high-altitude region. In the low altitude region, RFM = 1 + 0.205 × (1 − RFCD) − 0.246 × (1 − RFCD)2, and the RFMmax(1.043) was obtained under the treatments with RFCD = 0.58 (removed PE after covering for 75 days). The findings determined the optimum film (PE) covering period of tobacco and provided a crucial theoretical basis for the degradable polymer film material design, synthesis, and manufacturing in different regions.

Ultra-high molecular weight polyethylene (UHMWPE) possesses distinctive properties, but has an extremely low melt flow rate (MFR) of about zero, which makes it unsuitable for processing by standard methods for polymers. The aim of this paper was to investigate the tribological properties of two-component UHMWPE-based composites with different content of isotactic PP. The composites were fabricated by three methods: a) hot pressing of the powder mixtures; b) hot compression of granules; and c) 3D printing (FDM). It was shown that the UHMWPE-based composites obtained by extrusion compounding (hot compression of granules and 3D printing) in terms of the mechanical and tribological properties (wear resistance, the friction coefficient, Young's modulus, and yield strength) were superior to the ones manufactured by hot pressing of the powder mixtures. The most effective was the ‘UHMWPE+20% PP’ composite in terms of maintaining high tribological and mechanical properties and the necessary melt flow rate (MFR) in a wide range of loads. It was recommended as a feedstock for additive manufacturing of complex-shaped products (joint components) for friction units in orthopedics.

This paper presents the results of an investigation of the influence of the aluminum-powder concentration on the thermomechanical characteristics of the composites based on the high-density polyethylene. We show that use of a compatibilizer—maleic anhydride–polyethylene graft copolymer—in a mixture with high-density polyethylene has an influence on the regularity of variation of the thermomechanical curves. We study the influence of various cross-linking agents (dicumyl peroxide and sulfur) on the thermomechanical properties of composites. At a particular dicumyl peroxide and sulfur concentration, the composites might reside in three physical states: solid, highly elastic, and viscous flow.

Polypropylene/epoxy/synthetic graphite (PP/EP/SG) and high-density polyethylene (HDPE/EP/SG) composites were prepared by melt mixing followed by compression molding. The immiscibility of the polyolefins with epoxy was confirmed by thermogravimetric analysis. Scanning electron microscopy (SEM) studies showed that HDPE/EP blend exhibits inferior interfacial adhesion between the component polymers compared to PP/EP blend. Also, the effect of SG content on flexural properties, density, moldability, water absorption, and porosity of the PP/EP/SG and HDPE/EP/SG composites was investigated. For both PP/EP/SG and HDPE/EP/SG composites, flexural modulus, density, and porosity increased with increase in SG content. For PP/EP/SG composites, the water absorption decreased from 0.154% at 30 wt% SG to 0.072% at 70 wt% SG. Further increase in SG content to 80 wt% caused an increase in water absorption. On the other hand, water absorption for HDPE/EP/SG increased with SG content all through. At the same filler loadings, PP/EP/SG composites showed lower density and porosity and performed better in terms of flexural modulus and water absorption compared to HDPE/EP/SG composites.

A series of mono- and polynuclear bis(phenoxy-imine) titanium and zirconium complexes were synthesized. The complexes were immobilized on an MgCl2 carrier prepared by different methods. The homogeneous complexes and supported catalysts were evaluated for ethylene polymerization. The effects of the nuclearity of the precatalysts, nature of organoaluminum activator and the polymerization temperature were examined. It has been shown that immobilized on MgCl2 catalysts are superior in activity to homogeneous precatalysts by the level of activity (up to 6.1 ton of PE (molM h atm)−1). The precatalysts obtained in situ by the interaction of FI complexes, Bu2Mg and Et2AlCl are suitable for preparing ultra-high molecular weight polyethylene (UHMWPE) with molecular weight up to 6 106 Da even at elevated reaction temperatures. In addition, supported precatalysts, in the presence of MAO, effectively catalyze the ethylene–higher olefin copolymerization (activity—up to 8.2 ton of copolymer (molM⋅h⋅atm)−1).

This article presents the results of a study of the effect of the filler content on the rheological properties of polymer composite materials based on high density polyethylene containing glass microbeads. The flow curves of the compositions were obtained by the method of capillary viscosimetry. Simple mathematical models have been constructed that allow estimating the viscosity of the compositions’ melts based on a given filler content.

The article presents the comparative characteristics of polyethylene pipes after a 50-year period of operation, lists the factors affecting the physical and mechanical properties of pipes and requiring consideration when conducting research. Practical possibilities of assessing the technical condition of long-term operating polyethylene gas pipelines and approaches to extending their service life are considered.

In this paper, the distribution of the electric field of medium voltage (MV) underground cable insulation made of polyethylene/copper nanoparticles (XLPE/Cu) is investigated. Three methods were est...

Thermoplastic elastomers, such as styrene–butadiene–styrene (SBS), significantly enhance the properties of asphalt binders. This study first highlights the drawbacks of binder modification using chemically grafted polyethylene (g-PE) and then demonstrates the process by which g-PE can be used in combination with SBS. The important role of chemical grafting, sulphur content, and melt flow index (MFI) value in obtaining practically usable ‘g-PE/SBS’ modified binders have been illustrated. The results show that ungrafted and g-PE produces modified binders with highly inferior properties, and the polymers phase separate from the binder within few hours of preparation. % Elastic recovery of the ungrafted and g-PE modified binders was 2 are the essential factors that resulted in acceptable ‘25/75’ g-PE/SBS modified binders. Cost analysis shows that the use of g-PE can reduce the overall cost of asphalt pavement. The strategy illustrated in this study can be adopted for low-cost polymers and the effective utilization of waste plastics.

The crystallization process of brushes of polyethylene chains is investigated using all-atom molecular dynamics simulations at degrees of polymerization of 40 and 120. Through temperature reduction...

The work aims to generalize the existing theoretical studies into the influence of geometrical dimensions of the Maddock element installed on the extruder screw on the mixing quality of polyethylene composition with a silicone rubber in order to establish theoretical laws of the process and to verify them experimentally. A mathematical model of the flow of polymer melts in the working gaps of a single-extruder screw with a Maddock mixing element is formulated. Numerical and simulation experiments were carried out, a technological scheme for producing a composition for an antifriction layer of protective tubes of fiber optic communication cables is proposed, and samples of the new composition were obtained.

The risk of leakage and low thermal conductivity severely hinder the wide application of phase change materials (PCMs). In this work, the high-density polyethylene/carbon nanotubes (HDPE/CNTs) porous scaffolds were successfully fabricated via a sacrificial template method followed by the general melt blending and water solvent etching. Subsequently, a series of paraffin wax HDPE/CNTs/PW composite PCMs were obtained combined with the simple vacuum impregnation method. The obtained HDPE/CNTs porous scaffolds can effectively avoid the leakage of PW, meanwhile, the thermal conductivity and electrical conductivity of HDPE/CNTs/PW-3:7 are increased by 2.94 times and 13 orders of magnitude compared with the HDPE/PW-3:7 respectively, also, it exhibits high phase change enthalpy (153.95 J/g for melting enthalpy and 152.82 J/g for crystallization enthalpy). From the above perspectives, the HDPE/CNTs/PW-3:7 has promising potential value in the application of light-to-thermal conversion, electro-to-thermal conversion and thermal energy storage.

The dynamics of recovery of the open porous structure in HDPE films, which are preliminarily uniaxially deformed in the medium of supercritical CO2 followed by shrinkage in the longitudinal direction, upon their repeated stretching in air is studied by structural mechanical methods. The process of shrinkage is accompanied by the approach of lamellas and the disappearance of the oriented fibrillar structure. The value of relative shrinkage may be as high as 70–80%. According to atomic force microscopy and small-angle X‑ray scattering, these polymer films “remember” their previous strain in CO2 and in their repeated stretching in air, which is not a physically active medium, and restore the fibrillar porous structure of crazes with similar parameters. The phenomenon of such a memory makes it possible to use PE films preliminarily formed by the mechanism of intercrystallite crazing followed by their subsequent relaxation in the freestanding state as “precursors” for producing mesoporous materials with the pore volume on the order of 30 vol % for application in various fields, in particular, as vapor permeable membranes.

The relationship between the local topology of molecular entanglements at the nanosized scale and the mechanical properties at the macroscopic level is one of the open questions in polymer science. In this work, the process of pore formation in amorphous polyethylene during uniaxial stretching is modeled within the framework of the molecular dynamics method. It is considered how a change in the concentration of intermolecular entanglements affects the dynamics of the formation of nanosized pores. The results of the statistical analysis of pore sizes indicate that intermolecular entanglements slow down the processes of their growth and aggregation in the bulk of the polymer.