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ABSTRACT Background/Aim Materials and Methods Results Conclusions This study aims to evaluate and compare the impact absorption capacities of thermoformed ethylene vinyl acetate (EVA) mouthguards and 3D‐printed polyolefin mouthguards used in sports dentistry applications. The objective is to determine whether 3D‐printed polyolefin mouthguards offer superior impact toughness compared to traditional EVA mouthguards commonly used in sports settings.Six material samples were assessed: five pressure‐formed EVA mouthguards (PolyShok, Buffalo Dental, Erkoflex, Proform, and Drufosoft) and one 3D‐printed synthetic polymer (polyolefin). The materials were evaluated using a modified American Society for Testing and Materials (ASTM) D256 Test Method A for Izod pendulum impact resistance of plastics. Polyolefin samples were 3D‐printed using fused filament fabrication (FFF) technology. Notably, the FFF process included samples printed with notches placed either parallel or perpendicular to the build direction. This orientation served as a study factor, allowing for comparison of material behavior under different printing conditions. Impact testing was conducted using an Izod impact tester to assess the materials' performance under controlled impact conditions.The study achieved a high power (1.0) in power analysis, indicating strong sensitivity to detect significant differences. Among molded materials, PolyShok showed significantly lower impact toughness compared to others (p = 0.06). The mean impact absorption of EVA materials was 5.4 ± 0.3 kJ/m2, significantly lower than polyolefin materials, which demonstrated 12.9 ± 0.7 kJ/m2 and superior performance (p = 0.0). Horizontal‐notched polyolefin samples exhibited higher impact strength compared to vertical‐notched samples (p = 0.009).3D‐printed polyolefin mouthguards exhibited significantly higher impact toughness than thermoformed EVA mouthguards. While EVA materials demonstrated structural robustness, their lower impact resistance and observed tearing in other test specimens suggest the need for alternative testing standards to better reflect real‐world conditions. 3D‐printed mouthguards fabricated with build orientations perpendicular to the direction of impact demonstrate significantly enhanced impact absorption. Further research into manufacturing methods and testing protocols is recommended to optimize mouthguard performance under impact scenarios. [ABSTRACT FROM AUTHOR]

To access degradable polyolefin plastic, non‐alternating copolymerization of ethylene (E) and carbon monoxide (CO) for producing polyethylene (PE) with in‐chain ketones is particularly appealing; however, it still presents significant challenges such as molecular weight modulation (hydrogen response) and chain endgroup control (functional terminal). In this study, we achieved hydrogen‐controlled E/CO non‐alternating copolymerization using late transition metal catalysts. This process results in linear PEs containing the desired non‐alternating in‐chain keto groups (1.0–9.3 mol %) and with tunable molecular weights ranging from 43 to 195 kDa. In this reaction, H2 serves as a chain transfer agent, modulating the polymer's molecular weight, forming unique aldehyde endgroups and eliminating usual olefinic endgroups; CO undergoes non‐alternating insertion into the PE chain, resulting in a strictly non‐alternating structure (>99 %) for the keto‐PE. The dispersed incorporation of in‐chain keto groups retains bulk properties of PE and makes PE susceptible to photodegradation, which produces significantly lower molecular weight polymers and oligomers with unambiguous vinyl and acetyl terminals. [ABSTRACT FROM AUTHOR]

Polymerization of primary amine‐containing monomers is challenging because the amine inhibits polymerization catalyst activity. An alternative approach to access primary amine functionalized polymers is postpolymerization modification. To this end, the hydroaminoalkylation of vinyl‐terminated polyolefins with N‐(trimethylsilyl)benzylamine is used to prepare primary amine‐terminated polyolefins, with the free primary amine substituent being revealed upon hydrolytic work up. These materials are spectroscopically characterized, and an investigation of thermal properties by differential scanning calorimetry and thermogravimetric analysis is completed. These results show that the primary amine substituent increases the glass transition temperature and improves thermal stability. The reactive primary amine functionality is used in the photo‐oxidative dimerization of polyolefins to demonstrate how this elusive functionality can be applied in oligomer valorization. [ABSTRACT FROM AUTHOR]

Olefin polymerization is one of the most important chemical reactions in industry. This work presents a strategy that emphasizes the synergistic meta/para-steric hindrance of N-aryl groups and electronic effects in newly synthesized neutral salicylaldiminato nickel catalysts. These nickel(II) catalysts exhibit exceptional thermostability, ranging from 30 °C to 130 °C, demonstrating enhanced catalytic activities and broadly regulated polyethylene molecular weights (3–341 kg·mol−1) and controlled polymer branch density (2–102 brs/1000C). The preferred catalyst Ni3 with concerted steric and electronic effects enables the production of solid-state semi-crystalline polyethylene materials at temperatures below 90 °C. Notably, Ni3 exhibits an impressive tolerance of 110 °C and can withstand even the challenging polymerization temperature of 130 °C, leading to the production of polyethylene wax and oil. Also, functionalized polyethylene is produced. [ABSTRACT FROM AUTHOR]

This work demonstrates the potentials of a commercially available few-layer graphene (FLG) in enhancing the electro-dissipative properties, mechanical strength, and UV protection of polyolefin blend composites; interesting features of electronic packaging materials. Polyethylene (PE)/ polypropylene (PP)/ FLG blend composites were prepared following two steps. Firstly, different concentrations of FLG were mixed with either the PE or PP phases. Subsequently, in the second step, this pre-mixture was melt-blended with the other phase of the blend. FLG-filled composites were characterized in terms of electrical conductivity, morphological evolution upon shear-induced deformation, mechanical properties, and UV stability of polyolefin blend composites. Premixing of FLG with the PP phase has been observed to be a better mixing strategy to attain higher electrical conductivity in PE/PP/FLG blend composite. This observation is attributed to the influential effect of FLG migration from a thermodynamically less favourable PP phase to a favourable PE phase via the PE/PP interface. Interestingly, the addition of 4 wt.% (~2 vol.%) and 5 wt.% (~2.5 vol.%) of FLG increased an electrical conductivity of ~10 orders of magnitude in PE/PP—60/40 (1.87 × 10−5 S/cm) and PE/PP—20/80 (1.25 × 10−5 S/cm) blends, respectively. Furthermore, shear-induced deformation did not alter the electrical conductivity of the FLG-filled composite, indicating that the conductive FLG network within the composite is resilient to such deformation. In addition, 1 wt.% FLG was observed to be sufficient to retain the original mechanical properties in UV-exposed polyolefin composites. FLG exhibited pronounced UV stabilizing effects, particularly in PE-rich blends, mitigating surface cracking and preserving ductility. [ABSTRACT FROM AUTHOR]

Designing the catalysts to get high molecular weight polyethylene is an art. The catalysts bearing imine functionality derived from 8‐arylnaphthyl amines are more impressive and attractive in this regard. In this work, we synthesize 2,4‐dibenzhydryl‐8‐(3,5‐dichlorophenyl)naphthalen‐1‐amine to condense with picolinaldehyde, pyridine‐N‐oxide‐2‐carbaldehyde and 3,4‐dibutanone and then subsequently the treatment of resulting ligands with nickel precursors to get the corresponding catalysts. It was hypothesized that 3,5‐dichlorophenyl having extended wings of chlorine atoms along with bulky dibenzhydryl groups can provide good shielding on both apical positions of metal in response to slow down the chain transfer. More interestingly, the polymerization was done in industrially claimed n‐heptane solvent. All the catalysts showed activity in an order of 106, whereas a value of 1.04 × 107 g mol−1 h−1 has been recorded from keto‐imine based Ni‐3 catalyst. All catalysts generates polymer with high molecular weight with maximum value was recorded by Ni‐2 up to 37.4 × 104 g mol−1. Ni‐3 can also incorporate methyl 10‐undecenoate up to 2.6% in polyethylene backbone. [ABSTRACT FROM AUTHOR]

A kinetic/mechanistic investigation of gaseous propane hydrogenolysis over the single-site heterogeneous polyolefin depolymerization catalysts AlS/ZrNp2 and AlS/HfNp2 (AlS = sulfated alumina, Np = neopentyl), is use to probe intrinsic catalyst properties without the complexities introduced by time- and viscosity-dependent polymer medium effects. In a polymer-free automated plug-flow catalytic reactor, propane hydrogenolysis turnover frequencies approach 3,000 h-1 at 150 °C. Both catalysts exhibit approximately linear relationships between rate and [H2] at substoichiometric [H2] with rate law orders of 0.66 ± 0.09 and 0.48 ± 0.07 for Hf and Zr, respectively; at higher [H2], the rates approach zero-order in [H2]. Reaction orders in [C3H8] and [catalyst] are essentially zero-order under all conditions, with the former implying rapid, irreversible alkane binding/activation. This rate law, activation parameter, and DFT energy span analysis support a scenario in which [H2] is pivotal in one of two plausible and competing rate-determining transition states--bimolecular metal-alkyl bond hydrogenolysis vs. unimolecular β-alkyl elimination. The Zr and Hf catalyst activation parameters, ΔH‡ = 16.8 ± 0.2 kcal mol-1 and 18.2 ± 0.6 kcal mol-1, respectively, track the relative turnover frequencies, while ΔS‡ = -19.1 ± 0.8 and -16.7 ± 1.4 cal mol-1 K-1, respectively, imply highly organized transition states. These catalysts maintain activity up to 200 °C, while time-on-stream data indicate multiday activities with an extrapolated turnover number ~92,000 at 150 °C for the Zr catalyst. This methodology is attractive for depolymerization catalyst discovery and process optimization. [ABSTRACT FROM AUTHOR]

Heterogenization of nickel‐based olefin polymerization catalysts has received increasing attention in recent years. In this contribution, positional heterogenization effect in salicylaldimine nickel catalyzed ethylene polymerization is studied. The salicylaldimine nickel pre‐catalysts bearing anchor groups are synthesized, characterized, and investigated in heterogeneous catalytic ethylene polymerization. The anchoring groups are installed at different positions, including the 4‐position of the salicylaldehyde moiety and the 4‐position of the aniline moiety. It is shown that the positions of the anchoring groups have significant effects on heterogeneous ethylene polymerization catalyzed by SiO2‐supported salicylaldimine nickel catalysts. This provides a strategy worth considering for the design of high‐performance heterogeneous catalysts in the future. [ABSTRACT FROM AUTHOR]

Virgin and environmentally aged polypropylene (PP) micropowders (V-PP and E-PP, respectively) were used as reference microplastics (MPs) in comparative photo- and thermo-oxidative ageing experiments performed on their mixtures with a natural ferrous sand (NS) and with a metal-free silica sand (QS). The ferrous NS was found to catalyze the photo-oxidative degradation of V-PP after both UV and simulated solar light irradiation. The catalytic activity in the V-PP/NS mixture was highlighted by the comparatively higher fraction of photo-oxidized PP extracted in dichloromethane, and the higher carbonyl index of the bulk polymer extracted with boiling xylene, when compared with the V-PP/QS mixture. Similarly, NS showed a catalytic effect on the thermal degradation (at T = 60 °C) of E-PP. The results obtained indicate that, under suitable environmental conditions (in this case, an iron-containing sediment or soil matrix, combined with simulated solar irradiation), the degradation of some types of MPs could be much faster than anticipated. Given the widespread presence of iron minerals (including the magnetite and iron-rich serpentine found in NS) in both coastal and mainland soils and sediments, a higher than expected resilience of the environment to the contamination by this class of pollutants is anticipated, and possible routes to remediation of polluted natural environments by eco-compatible iron-based minerals are envisaged. [ABSTRACT FROM AUTHOR]

In this contribution, a series of unsymmetric α‐diimine nickel complexes are synthesized. One side of these nickel complexes is the 2,4‐dimethyl‐6‐diphenylmethylaniline unit, and the steric effects are tuned by changing another aniline unit. These nickel complexes have high catalytic activities in ethylene (>106 g mol−1 h−1) and 1‐octene (104–105 g mol−1 h−1) polymerization, generating high‐molecular‐weight polyolefins (Mn > 104 g mol−1) with tunable branching densities (59–91/1000C). Steric effects and polymerization temperature can significantly affect the catalytic performance of the catalyst. Most importantly, catalysts with different steric hindrances have different temperature sensitivity. In general, catalysts with larger steric hindrances are more sensitive to temperature. This may be due to the fact that the rotation of some chemical bonds is blocked at low temperatures due to the larger volume of the substituents, resulting in more significant temperature sensitivity. [ABSTRACT FROM AUTHOR]

Using linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) as polyolefin materials and boron nitride (BN) as thermal conductivity filler, the LLDPE/POE/BN thermal conductivity composites was prepared by melt blending hot pressing method. The influence of the process on the dispersion structure of BN was studied, and the relationship between the structure and thermal conductivity of the composites was discussed. The thermal conductivity and temperature field of the composites were predicted by finite element simulation. The results show that the composites with different BN dispersion structures are obtained by three processes. The cocontinuous structure composites formed by BN dispersed in LLDPE phase has excellent thermal conductivity. When the mass fraction of BN is 40% and 50%, the thermal conductivity of the composites is 0.72 W/(m·K) and 0.91 W/(m·K), respectively. Based on the dispersion structure of BN, the structure model of the composites was constructed, the thermal conductivity of the composites was predicted successfully, and the better heat transfer behavior of the composites was revealed. [ABSTRACT FROM AUTHOR]

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Heat‐shrinkable films commonly serve as active materials for self‐folding owing to their capability to fold all hinges upon heating. For origami‐based electronic devices, the self‐folding of the metal layer is necessary. Nevertheless, the self‐folding angle is low owing to the high bending stiffness of metal layers and the low adhesion of heat‐shrinkable films. Here, we introduce a bilayer self‐folding technique that effectively suppresses delamination of the shrink layer, thereby achieving a high folding force and angle. A polyolefin film mechanically fixed on the metal substrate serves to inhibit delamination, regardless of the adhesive properties of the shrink layer. This is achieved by applying adhesives within holes fabricated on the shrink layer. Conventional methods using an adhesive layer to fix the shrink layer lead to delamination at temperatures above 100°C, resulting in a decrease in self‐folding angles. In contrast, our novel fixing method yields a folding angle of 161° at 140°C, with a shrinkage rate of 69%. To demonstrate the versatility of our proposed technique, we self‐fold various origami structures, including Miura‐ori, scissors, cranes, and tessellation with chip LEDs. The introduced method broadens the range of substrate materials suitable for self‐folding and offers new possibilities for the development of origami devices. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The present study focuses on the effect of octylphenoxy poly(ethyleneoxy)ethanol (IGEPAL CA 630) on the environmental stress cracking resistance (ESCR) of blends of polypropylene (PP) and low-density polyethylene (LDPE) at different weight fractions without and with the addition of two compatibilizers, corresponding to styrene-ethylene-butylene-styrene (SEBS) copolymer and styrene-ethylene-butylene maleate (SEBS-g-MA). Compression molding was used after mixing the melt in a Brabender internal mixer to create the blends. ESCR of the blends was determined by exposing the blends to a solution of IGEPAL CA 630 the presence of stress. Mechanical (tensile) and thermal properties are extracted to evaluate the effect of adding the compatibilizers SEBS and SEBS-g-MA to the blend. In the environmental stress cracking (ESCR) tests, the time to failure increases with increasing PP content, despite PP's greater resistance to ESCR than LDPE. The addition of SEBS-g-MA to the blend significantly improves the flexibility and ESCR performance of PP/LDPE blends with specific weight fractions. [ABSTRACT FROM AUTHOR]

The recycling of plastic packaging wastes helps to alleviate the problems of white pollution and resource shortage. It is very necessary to develop high-value conversion technologies for plastic packaging wastes. To our knowledge, carbon materials with excellent properties have been widely used in energy storage, adsorption, water treatment, aerospace and functional packaging, and so on. Waste plastic packaging and biomass materials are excellent precursor materials of carbon materials due to their rich sources and high carbon content. Thus, the conversion from waste plastic packaging and biomass materials to carbon materials attracts much attention. However, closely related reviews are lacking up to now. In this work, the pyrolysis routes of the pyrolysis of plastic packaging wastes and biomass materials for conversion to high-value carbons and the influence factors were analyzed. Additionally, the applications of these obtained carbons were summarized. Furthermore, the limitations of the current pyrolysis technology are put forward and the research prospects are forecasted. Therefore, this review can provide a useful reference and guide for the research on the pyrolysis of plastic packaging wastes and biomass materials and the conversion to high-value carbon. [ABSTRACT FROM AUTHOR]

This work investigated the photostabilizing role of a commercially available few-layer graphene (FLG) in mixed polyolefins waste stream (MPWS), ensuring extended lifespan for outdoor applications. The investigation was conducted by analyzing carbonyl content increase, surface appearance, and the retention of mechanical properties of UV-exposed MPWS/FLG composites. Despite the likely predegraded condition of MPWS, approximately 60%, 70%, 80%, and 90% of the original ductility was retained in composites containing 1, 4, 7, and 10 wt.% FLG, respectively. Conversely, just 20% of the original ductility was retained in unfilled MPWS. Additionally, less crack density and lower carbonyl concentrations of the composites also highlighted the photoprotection effect of FLG. For prime polyolefin blends, only 0.5 wt.% or 1 wt.% FLG was sufficient to preserve the original surface finishing and protect the mechanical properties from photodegradation. Hence, it was observed that MPWS requires more FLG than prime polyolefin blends to get to comparable property retention. This could be attributed to the poor dispersion of FLG in MPWS and inevitable uncertainties such as the presence of impurities, pre-degradation, and polydispersity associated with MPWS. This study outlines a potential approach to revalorize MPWS that possess a minimal intrinsic value and would otherwise be destined for landfill disposal. [ABSTRACT FROM AUTHOR]

Improper disposal of waste plastic has caused serious ecological and environmental pollution problems. Transforming plastics into high value-added chemicals can not only achieve efficient recycling of waste plastics, but is also an effective way to control white pollution. The catalyst selectively breaks the C–C bond of polyolefin plastic under heat treatment and converts it into liquid fuel, thus realizing sustainable recycling of plastics and has a good development prospect. This review provides a detailed overview of the current development of catalytic pyrolysis, catalytic hydrolysis, solvent decomposition, and supercritical hydrothermal liquefaction for cracking plastics to make fuel oil. The reaction mechanism, influencing factors, and promoting effects of catalysts in various degradation technologies are analyzed and summarized, and the latest proposed tandem reaction for degrading plastics is briefly introduced. Finally, some optimization paths of waste plastic pyrolysis to fuel oil technology are proposed: synergies between mixed raw materials, in-depth exploration of catalysts, design and manufacture of reactors that match the pyrolysis technology. All these are important research directions for promoting the industrialization of plastic pyrolysis to fuel oil. [ABSTRACT FROM AUTHOR]

Ultra-high molecular weight polyolefin (UHMWPO) has enormous potential applications due to their excellent mechanical properties such as tensile strength, flexural modulus, toughness and outstanding chemical resistance. But the processing of polyolefin, in particular, UHMWPO fibers cannot be processed by conventional methods due to its very high melt viscosity. In this work, we synthesized isotactic ultra-high molecular weight polypropylene (UHMWPP) resin and studied the processability of UHMWPP fibers using gel spinning and investigated physicomechanical properties. UHMWPP gel was made at various concentrations in decalin solvent at 150°C to produce consistent spinning dope solutions. The 7 wt.% concentration of UHMWPP was deemed best for fiber creation, compared to 3 wt.% and 5 wt.%. A rheological time sweep was done to ensure the gel's stability at 170°C before the spinning process. The UHMWPP's gelation and fiber formation were studied by tweaking the gel concentration and adjusting the processing temperature. The resulting UHMWPP monofilament had a measure of 220-250 denier. The hot stretched fibers were analyzed with the scanning electron microscope (SEM) to understand the surface morphology of the fibers. The crystal morphology of UHMWPP fibers was measured with wide-angle x-ray scattering (WAXS) and DSC. The X-ray measurement of hot stretched UHMWPP fibers showed crystalline peaks compared to those without stretched fibers.

Polymers show a transition from ductile-to brittle fracture behavior at decreasing temperatures. Consequently, the material toughness has to be determined across wide temperature ranges in order to determine the Ductile-Brittle Transition Temperature This usually necessitates multiple impact experiments. We present a machine-learning methodology for the prediction of DBTTs from single Instrumented Puncture Tests Our dataset consists of 7,587 IPTs that comprise 181 Polyethylene and Polypropylene compounds. Based on a combination of feature engineering and Principal Component Analysis, relevant information of instrumentation signals is extracted. The transformed data is explored by unsupervised machine learning algorithms and is used as input for Random Forest Regressors to predict DBTTs. The proposed methodology allows for fast screening of new materials. Additionally, it offers estimations of DBTTs without thermal specimen conditioning. Considering only IPTs tested at room temperature, predictions on the test set hold an average error of 5.3°C when compared to the experimentally determined DBTTs. [ABSTRACT FROM AUTHOR]

Antioxidants are essential to the polymer industry. The addition of antioxidants delays oxidation and material degradation during their processing and usage. Sustainable phenolic acids such as 4-hydroxybenzoic acid or 3,4-dihydroxybenzoic acid were selected. They were chemically modified by esterification to obtain various durable molecules, which were tested and then compared to resveratrol, a biobased antioxidant, and Irganox 1076, a well-known and very efficient fossil-based antioxidant. Different sensitive matrices were used, such as a thermoplastic polyolefin (a blend of PP and PE) and a purposely synthesized thermoplastic polyurethane. Several formulations were then produced, with the different antioxidants in varying amounts. The potential of these different systems was analyzed using various techniques and processes. In addition to antioxidant efficiency, other parameters were also evaluated, such as the evolution of the sample color. Finally, an accelerated aging protocol was set up to evaluate variations in polymer properties and estimate the evolution of the potential of different antioxidants tested over time and with aging. In conclusion, these environmentally friendly antioxidants make it possible to obtain high-performance materials with an efficiency comparable to that of the conventional ones, with variations according to the type of matrix considered. [ABSTRACT FROM AUTHOR]

Ultra-high molecular weight polyolefin (UHMWPO) has enormous potential applications due to its excellent mechanical properties such as tensile strength, flexural modulus, toughness and outstanding chemical resistance. But the processing of polyolefin, in particular UHMWPO fibers, cannot be processed by conventional methods due to its very high melt viscosity. In this work, we synthesized isotactic ultra-high molecular weight polypropylene (UHMWPP) resin and studied the processability of UHMWPP fibers using gel spinning and investigated physicomechanical properties. UHMWPP gel was made at various concentrations in decalin solvent at 150°C to produce consistent spinning dope solutions. The 7 wt.% concentration of UHMWPP was deemed best for fiber creation, compared to 3 wt.% and 5 wt.%. A rheological time sweep was done to ensure the gel's stability at 170°C before the spinning process. The UHMWPP's gelation and fiber formation were studied by tweaking the gel concentration and adjusting the processing temperature. The resulting UHMWPP monofilament had a measure of 220-250 denier. The hot stretched fibers were analyzed with scanning electron microscopy (SEM) to understand the surface morphology of the fibers. The crystal morphology of UHMWPP fibers was measured with wide-angle X-ray diffractometry (WAXS) and DSC. The X-ray patterns of hot stretched UHMWPP fibers showed crystalline peaks compared to those without stretched fibers. [ABSTRACT FROM AUTHOR]

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

Chemical recycling enables plastics to be a part of the circular economy as it can cope with contaminated as well as mixed plastics waste. Herein, two important discoveries are reported. One innovation is the use of table salt (NaCl) to facilitate the low temperature pyrolysis of polyolefins comprised of high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), linear low‐density polyethylene (LLDPE), and polypropylene (PP) at the ratio of (4:2:2:3), respectively, thus enabling the efficient recycling of these mixed plastics. For comparative analysis, two different Pt catalysts as well as a control are investigated. Compared to the control, the use of table salt at 10 wt.% increased both the oil and gas contents by 80% and enabled 100% conversion to gas and oil without producing any undesirable wax. The second innovation is that metallized plastics are successfully pyrolyzed with table salt with excellent conversion efficiencies. The obtained oil fraction is further characterized using gas chromatography‐mass spectrometry (GC‐MS). In addition, the re‐use of salt, the effect of salt particle size and effect of the wt.% are explored. The thermal properties of the wax (solid) are characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Economic estimation revealed a 3.5‐fold increase in revenue can be generated by the novel method as compared to pyrolysis without any salt. In contrast, pyrolysis with a conventional Pt/alumina system incurs huge losses. These findings suggest that table salt can offer a transformative approach toward an inexpensive (4 cents per kg) and efficient pyrolysis methodology for the conversion of mixed plastics waste to useful hydrocarbon products. [ABSTRACT FROM AUTHOR]

The toxicity and density of smoke from 10 commonly used commercial polymer types was studied using the European railway standard EN 45545‐2. This test method was chosen because it reflects the current state‐of‐the‐art in assessing the hazards of smoke in bench‐scale test scenarios (not because of a specific link to railway applications). The study involves 72 commercially relevant formulations provided by 12 industrial companies. Polymers studied include PE, PP, PC, PA6, PA66, u‐PVC, p‐PVC, PU, PIR, and epoxy resins. Reference samples as well as samples containing halogenated and Phosphorus, Inorganic or Nitrogen based Flame Retardants (PIN FRs) were tested according to the French tubular furnace method (NF X 70‐100) to evaluate their smoke toxicity at 600°C and according to ISO 5659‐2 at 50 kW m−2 with Annex C of EN 45545‐2 to evaluate their smoke density as well as toxicity at 4 and 8 min. This study highlights that the measured toxicity and calculated Conventional Indexes of Toxicity (CITNLP, CIT4 min, CIT8 min), as well as maximum smoke density (DsMAX) show generally no significant increase in the presence of PIN FRs in comparison to the neat polymers. The use of intumescent FRs or hydroxide based FRs generally allows considerable smoke reduction with little impact on smoke toxicity. Bromine based‐FRs were found to be detrimental to both hazards in most matrices studied here. [ABSTRACT FROM AUTHOR]

This work demonstrates the potentials of a commercially available few-layer graphene (FLG) in enhancing the electro-dissipative properties, mechanical strength, and UV protection of polyolefin blend composites; interesting features of electronic packaging materials. Polyethylene (PE)/ polypropylene (PP)/ FLG blend composites were prepared following two steps. Firstly, different concentrations of FLG were mixed with either the PE or PP phases. Subsequently, in the second step, this pre-mixture was melt-blended with the other phase of the blend. FLG-filled composites were characterized in terms of electrical conductivity, morphological evolution upon shear-induced deformation, mechanical properties, and UV stability of polyolefin blend composites. Premixing of FLG with the PP phase has been observed to be a better mixing strategy to attain higher electrical conductivity in PE/PP/FLG blend composite. This observation is attributed to the influential effect of FLG migration from a thermodynamically less favourable PP phase to a favourable PE phase via the PE/PP interface. Interestingly, the addition of 4 wt.% (~2 vol.%) and 5 wt.% (~2.5 vol.%) of FLG increased an electrical conductivity of ~10 orders of magnitude in PE/PP—60/40 (1.87 × 10−5 S/cm) and PE/PP—20/80 (1.25 × 10−5 S/cm) blends, respectively. Furthermore, shear-induced deformation did not alter the electrical conductivity of the FLG-filled composite, indicating that the conductive FLG network within the composite is resilient to such deformation. In addition, 1 wt.% FLG was observed to be sufficient to retain the original mechanical properties in UV-exposed polyolefin composites. FLG exhibited pronounced UV stabilizing effects, particularly in PE-rich blends, mitigating surface cracking and preserving ductility.

This review considers the recent investigations in the scope of biodegradability of synthetic polymers, spanning polyethylene (PE), polypropylene (PP), and their corresponding composites, with a focus on the influence of oxo-additives (mostly transition metal salts). The types of oxo-additives and the mechanisms of oxidation acceleration are discussed. Furthermore, the influence of oxo-additives on both physicochemical and biological stages of degradation is evaluated (laboratory and field experiments with microorganisms/fungi action) with recent standards suggested for degradation estimation. Comparisons of the metal salts are given with respect to catalysis, as well as the synergetic influence of additives. The additives presented on the commercial market are also discussed.

Polymers show a transition from ductile-to brittle fracture behavior at decreasing temperatures. Consequently, the material toughness has to be determined across wide temperature ranges in order to determine the Ductile-Brittle Transition Temperature This usually necessitates multiple impact experiments. We present a machine-learning methodology for the prediction of DBTTs from single Instrumented Puncture Tests Our dataset consists of 7,587 IPTs that comprise 181 Polyethylene and Polypropylene compounds. Based on a combination of feature engineering and Principal Component Analysis, relevant information of instrumentation signals is extracted. The transformed data is explored by unsupervised machine learning algorithms and is used as input for Random Forest Regressors to predict DBTTs. The proposed methodology allows for fast screening of new materials. Additionally, it offers estimations of DBTTs without thermal specimen conditioning. Considering only IPTs tested at room temperature, predictions on the test set hold an average error of 5.3°C when compared to the experimentally determined DBTTs.

This study features comprehensive physical and electrochemical properties of different polyolefin and non-polyolefin separators. These separators include polypropylene-polyethylene-polypropylene (PEP), polyethylene (PE), Al2O3-coated polypropylene (C-PP), polyethylene terephthalate (PET), and Silicon carbide mat (SiCmat). The interaction of the different separators and the electrolyte was investigated in terms of ionic conductivity, contact angle test, electrolyte uptake, and electrolyte oxidation. The full cells fabricated using the different separators were also studied for charge–discharge performance, cycle performance, and internal resistance. Results showed that the different separators demonstrated different physical and electrochemical behavior. The non-polyolefin separators registered a small electrolyte contact angle due to their high porosity and structural compatibility with the electrolyte. At 10 C-Rate, the specific capacity is in the order of PET > SiCmat > C-PP > PE > PEP corresponding to 90 mAh/g, 85 mAh/g, 70 mAh/g, 60 mAh/g and 40 mAh/g respectively. After 100 cycles at 1.0 C-rate, the cycle performance is in the order of PE > PET > C-PP > SiCmat > PEP corresponding to 70 %, 65 %, 61 %, 51 % and 49 % respectively. Thermally, PET, C-PP and SiCmat showed better thermal stability compared to the other separators. Therefore, Industrial production that requires high thermal stability may rely on C-PP, PET, or SiCmat, while PET and SiCmat offer better cycle performance and may replace commercially available PE and PEP.

Fast scanning calorimetry (FSC) enables rapid sample cooling from the melt at rates of several thousand Kelvin per second. A perfect amorphous state for polypropylene (PP) can be achieved by fast cooling at rates of 5000 K s-1. In comparison, polyethylene (PE) crystallizes during cooling, even at cooling rates accessible with FSC. Thus, in this study, a novel method was proposed for determining the PP/PE mixing ratio with a standard deviation of 1.4 mass% that combines FSC and differential scanning calorimetry. The proposed method considers the above thermal behavior of the components of polyolefin blends. In addition, the proposed method is expected to provide a convenient way to analyze the composition of recycled polyolefins from the market or industrial processes without the need for high-temperature solvents that are typically used in nuclear magnetic resonance or for calibration curves in Fourier transform infrared spectrophotometry. [ABSTRACT FROM AUTHOR]

Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR‐b‐PE diblock copolymers were synthesized using the {Me2Si(C13H8)2Nd(BH4)2Li(THF)}2 complex in combination with n‐butyl,n‐octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi‐crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl‐1,5‐di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization‐driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers. [ABSTRACT FROM AUTHOR]

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Additive manufacturing (AM) nowadays has become a supportive method of traditional manufacturing. In particular, the medical and healthcare industry can profit from these developments in terms of personalized design and batches ranging from one to five specimens overall. In terms of polymers, polyolefins are always an interesting topic due to their low prices, inert chemistry, and crystalline structure resulting in preferable mechanical properties. Their semi-crystalline nature has some advantages but are challenging for AM due to their shrinkage and warping, resulting in geometrical inaccuracies or even layer detaching during the process. To tackle these issues, process parameter optimization is vital, with one important parameter to be studied more in detail, the print envelope temperature. It is well known that higher print envelope temperatures lead to better layer adhesion overall, but this investigation focuses on the mechanical properties and resulting morphology of a semi-crystalline thermoplastic polyolefin. Further, two different AM technologies, namely material jetting (ARBURG plastic freeforming—APF) and filament-based material extrusion, were studied and compared in detail. It was shown that higher print envelope temperatures lead to more isotropic behavior based on an evenly distributed morphology but results in geometrical inaccuracies since the material is kept in a molten state during printing. This phenomenon especially could be seen in the stress and strain values at break at high elongations. Furthermore, a different crystal structure can be achieved by setting a specific temperature and printing time, also resulting in peak values of certain mechanical properties. In comparison, better results could be archived by the APF technology in terms of mechanical properties and homogeneous morphology. Nevertheless, real isotropic part behavior could not be managed which was shown by the specimen printed vertically. Hence, a sweet spot between geometrical and mechanical properties still has to be found. [ABSTRACT FROM AUTHOR]

The crystallization properties of polypropylene (PP), a widely used polymer in industry, can be modified to overcome its mechanical limitations. In the current work, we investigated the effect of ethylene octene copolymer (EOC), blend morphology, nanoclay loading, nano‐localization, and component ratios on PP/EOC crystallization behavior in various aspects, including crystallization rate, degree of crystallinity, nucleation state, and crystalline phases. The results revealed that adding EOC with varying ratios can decrease PP crystallinity both in degree and rate due to the partial miscibility of components through grafting. Furthermore, it was found that the effect of the nanoclay on the crystallization behavior of PP is dependent on the nanoclay loading and its localization in the blend. The nanoclay, therefore, served as a nucleation agent at low nanoparticle contents, accelerating the crystallization rate regardless of the blend's microstructure. However, the crystallization rate of the blend samples at high nanoclay contents (above the rheological percolation threshold) was strongly influenced by the type of morphology. Accordingly, high nanoclay concentrations in blends with matrix‐dispersed morphologies reduced crystallization rates (increasing half‐time from 164 to 216 and 186 s), primarily because PP chains slowed down due to their interactions with nanoparticles and nanoclay hindrance. In contrast, in a blend with a co‐continues‐type morphology, the crystallization rates increased (decreasing half‐time from 624 to 270 and 236 s) due to nano‐localization at the interface and morphology transformation to the matrix‐dispersed one. The blends and nanocomposites based on PP/EOC were also investigated to determine the relationship between the crystallization behavior and mechanical properties. [ABSTRACT FROM AUTHOR]

This review considers the recent investigations in the scope of biodegradability of synthetic polymers, spanning polyethylene (PE), polypropylene (PP), and their corresponding composites, with a focus on the influence of oxo-additives (mostly transition metal salts). The types of oxo-additives and the mechanisms of oxidation acceleration are discussed. Furthermore, the influence of oxo-additives on both physicochemical and biological stages of degradation is evaluated (laboratory and field experiments with microorganisms/fungi action) with recent standards suggested for degradation estimation. Comparisons of the metal salts are given with respect to catalysis, as well as the synergetic influence of additives. The additives presented on the commercial market are also discussed. [ABSTRACT FROM AUTHOR]

The recycling of plastic packaging wastes helps to alleviate the problems of white pollution and resource shortage. It is very necessary to develop high-value conversion technologies for plastic packaging wastes. To our knowledge, carbon materials with excellent properties have been widely used in energy storage, adsorption, water treatment, aerospace and functional packaging, and so on. Waste plastic packaging and biomass materials are excellent precursor materials of carbon materials due to their rich sources and high carbon content. Thus, the conversion from waste plastic packaging and biomass materials to carbon materials attracts much attention. However, closely related reviews are lacking up to now. In this work, the pyrolysis routes of the pyrolysis of plastic packaging wastes and biomass materials for conversion to high-value carbons and the influence factors were analyzed. Additionally, the applications of these obtained carbons were summarized. Furthermore, the limitations of the current pyrolysis technology are put forward and the research prospects are forecasted. Therefore, this review can provide a useful reference and guide for the research on the pyrolysis of plastic packaging wastes and biomass materials and the conversion to high-value carbon.

This work investigated the photostabilizing role of a commercially available few-layer graphene (FLG) in mixed polyolefins waste stream (MPWS), ensuring extended lifespan for outdoor applications. The investigation was conducted by analyzing carbonyl content increase, surface appearance, and the retention of mechanical properties of UV-exposed MPWS/FLG composites. Despite the likely predegraded condition of MPWS, approximately 60%, 70%, 80%, and 90% of the original ductility was retained in composites containing 1, 4, 7, and 10 wt.% FLG, respectively. Conversely, just 20% of the original ductility was retained in unfilled MPWS. Additionally, less crack density and lower carbonyl concentrations of the composites also highlighted the photoprotection effect of FLG. For prime polyolefin blends, only 0.5 wt.% or 1 wt.% FLG was sufficient to preserve the original surface finishing and protect the mechanical properties from photodegradation. Hence, it was observed that MPWS requires more FLG than prime polyolefin blends to get to comparable property retention. This could be attributed to the poor dispersion of FLG in MPWS and inevitable uncertainties such as the presence of impurities, pre-degradation, and polydispersity associated with MPWS. This study outlines a potential approach to revalorize MPWS that possess a minimal intrinsic value and would otherwise be destined for landfill disposal.

Improper disposal of waste plastic has caused serious ecological and environmental pollution problems. Transforming plastics into high value-added chemicals can not only achieve efficient recycling of waste plastics, but is also an effective way to control white pollution. The catalyst selectively breaks the C–C bond of polyolefin plastic under heat treatment and converts it into liquid fuel, thus realizing sustainable recycling of plastics and has a good development prospect. This review provides a detailed overview of the current development of catalytic pyrolysis, catalytic hydrolysis, solvent decomposition, and supercritical hydrothermal liquefaction for cracking plastics to make fuel oil. The reaction mechanism, influencing factors, and promoting effects of catalysts in various degradation technologies are analyzed and summarized, and the latest proposed tandem reaction for degrading plastics is briefly introduced. Finally, some optimization paths of waste plastic pyrolysis to fuel oil technology are proposed: synergies between mixed raw materials, in-depth exploration of catalysts, design and manufacture of reactors that match the pyrolysis technology. All these are important research directions for promoting the industrialization of plastic pyrolysis to fuel oil.

Management of the plastic industry is a momentous challenge, one that pits enormous societal benefits against an accumulating reservoir of nearly indestructible waste. A promising strategy for recycling polyethylene (PE) and isotactic polypropylene (iPP), constituting roughly half the plastic produced annually worldwide, is melt blending for reformulation into useful products. Unfortunately, such blends are generally brittle and useless due to phase separation and mechanically weak domain interfaces. Recent studies have shown that addition of small amounts of semicrystalline PE-iPP block copolymers (ca. 1 wt%) to mixtures of these polyolefins results in ductility comparable to the pure materials. However, current methods for producing such additives rely on expensive reagents, prohibitively impacting the cost of recycling these inexpensive commodity plastics. Here, we describe an alternative strategy that exploits anionic polymerization of butadiene into block copolymers, with subsequent catalytic hydrogenation, yielding E and X blocks that are individually melt miscible with PE and iPP, where E and X are poly(ethylene-ran-ethylethylene) random copolymers with 6 wt% and 90 wt% ethylethylene repeat units, respectively. Cooling melt blended mixtures of PE and iPP containing 1 wt% of the triblock copolymer EXE of appropriate molecular weight, results in mechanical properties competitive with the component plastics. Blend toughness is obtained through interfacial topological entanglements of the amorphous X polymer and semicrystalline iPP, along with anchoring of the E blocks through cocrystallization with the PE homopolymer. Significantly, EXE can be inexpensively produced using currently practiced industrial scale polymerization methods, offering a practical approach to recycling the world's top two plastics. [ABSTRACT FROM AUTHOR]

The (stereoselective) living coordinative copolymerization of 1‐alkenes with 4‐aryl‐1,6‐heptadienes, in both the absence and presence of multiple equivalents of a reversible chain transfer agent, is established as a highly versatile strategy for production of multivariate hyperdimensional functionalized semi‐crystalline or amorphous polyolefins that optionally possess either mono‐ or difunctionalized (telechelic) end‐groups in combination with a programmable level of incorporation of orthogonal functional groups within the main‐chain. The non‐conjugated diene comonomers are readily obtained from a diverse range of aryl carboxaldehyde precursors through a one‐step bis‐allylation process. These results serve to provide a new platform for exploring the science and technology of a vast new landscape of functionalized classes of polyolefins that are now accessible in practical and scalable quantities. [ABSTRACT FROM AUTHOR]

The exceptional low permeability to oxygen and water of PVDC and the retention of barrier properties to oxygen even in humid conditions explain its success for packaging in food industry as barrier layer in Polyolefins (PO) multilayer films, whose contribution to the reduction of food waste is largely recognized. Several chemical recycling technologies have emerged in the recent years that, together with methodologies based on separation of layers by the use of solvents, will strongly increase in a near future the extent of recycling of multilayer films, including the PVDC-containing ones. At the same time, it is generally accepted that for several years these technologies will be complemented by the now dominating mechanical recycling. A lack of detailed study in the literature and a general confusion between very different PVDC grades, with and without internal stabilization, led to the idea that the dehydrochlorination of PVDC would cause a low quality of the recyclate obtained by mechanical recycling of PO in presence of PVDC and a corrosion risk for the equipment. In this study, the effect of a stabilized PVDC grade developed for coextrusion, at concentration typical of real life PO mix for mechanical recycling and in suitable condition, has been investigated in a pilot scale extruder and corrosion tests were performed. In conclusion, quantities of PVDC to be found in PO streams for mechanical recycling are compatible with a PO recyclate of excellent characteristics, even at extrusion temperatures as high as 220°C, with no damage to the PO structure, with only minimum discoloration, that can be mitigated by relatively low quantities of additives of general use in PO extrusion, and with no risk of corrosion of the equipment. [ABSTRACT FROM AUTHOR]

Polyolefins with periodic unsaturation in the backbone chain are sought after for synthesizing chemically recyclable polymers or telechelic polyolefin macromonomers. Here we introduce a bottom‐up synthesis of unsaturated high‐density polyethylene (HDPE) via copolymerization of ethylene with dimethyl 7‐oxabicyclo[2.2.1]hepta‐2,5‐diene‐3,5‐dicarboxylate followed by post‐polymerization retro‐Diels–Alder to unveil hidden double bonds in the polymer backbone. The incorporation of this "Trojan Horse" comonomer was varied and a series of unsaturated HDPE polymers with block lengths of 1.2, 1.9, and 3.5 kDa between double bonds was synthesized. Cross metathesis of unsaturated HDPE samples with 2‐hydroxyethyl acrylate yielded telechelic ester terminated PE macromonomers suitable for the preparation of ester‐linked PE. These materials were depolymerized and repolymerized, making them suitable candidates for chemical recycling. The ester‐linked PE displayed thermal and mechanical properties comparable to commercial HDPE. [ABSTRACT FROM AUTHOR]

Disulfide bonds are dynamic covalent bonds, which are easy to cleave and reform upon chemical stimulus. Various methods including the oxidative coupling of thiols and polymerization of disulfide-containing monomers have been developed for the synthesis of poly(disulfide)s. However, installing small amounts of disulfide units in the main chain of polyolefins has received much less attention. Herein, we report a novel strategy for incorporating cleavable disulfide units into the backbone of polyolefins using commercially available diallyl disulfide (DADS) as a comonomer via metathesis copolymerization. The copolymerization of diallyl disulfide with cyclooctene occurred using the second-generation Grubbs catalyst under mild conditions, allowing for the synthesis of copolymers with adjustable disulfide content ranging from 0.7 to 8.5 mol%, and the molecular weight of the obtained copolymers ranged from 5.8 kg·mol−1 to 42.8 kg·mol−1. The resulting polyolefins with disulfide insertion retained excellent thermal processability and exhibited degradability. Treatment of the copolymer (8.5 mol% disulfide content) with tri-n-butylphosphine resulted in a significant reduction in molecular weight from 5.8 kg·mol−1 to 1.6 kg·mol−1. Successful copolymerization with diallyl disulfide provides a convenient and effective method for obtaining degradable polyolefins. [ABSTRACT FROM AUTHOR]

The functionalization of poly (1‐hexene) with maleic anhydride (MA) in the presence of benzoyl peroxide as initiator was investigated and the effect of reaction parameters such as initiator content, maleic anhydride concentrations, reaction temperature and reaction time were studied. Furthermore, changing the catalyst system from a commercial Ziegler‐Natta (TiCl4/MgCl2/Internal donor) to α‐diimine Nickel catalyst led to a higher degree of functionalization (DOF) thanks to higher unsaturation content of polymer chains made by the Nickel catalyst system. The obtained polymer moreover was contacted with polyethylene glycol methyl ether to ensure the attachment of the functionalizing agent on the poly (1‐hexene) chains. Different analyses were used to support the observations. For instance, thermogravimetric analysis (TGA) exhibited no weight loss at 210 °C for the sample confirming, the complete reaction of maleic anhydride, or FTIR analysis, where the presence of ester group bands was evidence for the reaction. [ABSTRACT FROM AUTHOR]

The degradation of plastics has attracted much attention from the global community. Polyethylenes (PEs), as the most abundant synthetic plastics, are most frequently studied. PE is non-degradable and non-polar because of the sole presence of the pure hydrocarbon components. Concurrent incorporation of both in-chain cleavable and functional groups into the PE chain is an effective pathway to overcome the non-degradable and non-polar issue; however, the method for achieving this pathway remains elusive. Here, we report a strictly non-alternating (>99%) terpolymerization of ethylene with CO and fundamental polar monomers via a coordination–insertion mechanism using late transition metal catalysts, which effectively prevents the formation of undesired chelates originating from both co-monomers under a low CO concentration. High-molecular-weight linear PEs with both in-chain isolated keto (>99%) and main-chain functional groups are prepared. The incorporation of key low-content isolated keto groups makes PEs photodegradable while retaining their desirable bulk material properties, and the introduction of polar functional groups considerably improves their surface properties. [ABSTRACT FROM AUTHOR]

Over the past three years, many unprecedented events have happened which have significantly influenced the whole world. This paper deals with several topical issues, such as the impact of the coronavirus pandemic on Brent's oil prices, on the price of plastics, specifically polyolefins, i.e., polyethene and polypropylene, price trends of petroleum products, in different crisis periods from 2006 to the present and predicts the price trend of petroleum products (polyolefins) using artificial intelligence. In the application part of the research, the following research methods were used: time series regression using neural networks and correlation and regression analysis. Neural networks confirmed a significant effect of the coronavirus pandemic on Brent's oil price. Correlation analysis showed a long-term comparable trend in the development of Brent oil and polyolefin prices, which is a confirmation of the significant impact of COVID-19 on the price of polyethene and polypropylene. The greatest benefit of this research for the application sphere is the prediction of the price development of polyolefins. All generated variants of the ANS neural network module predict a decreasing trend of polypropylene and polyethene prices until the end of 2023. The conducted research on the prices of polyolefins is a unique study with practical benefits for companies producing the most in-demand material in the world - plastic. Analysing and predicting the price development of the commodities under study can be useful for entities in their strategic assessment and subsequent investment decisions. A limitation of the research is the ongoing war conflict in Ukraine, as the oil market is sensitive to political conflicts and becomes difficult to control and predict. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to detect the effects of different polyolefin mixtures (polypropylene(PP): polyethylene(PE)) on the viscosity and temperature susceptibility of pure bitumen and was also aimed to comparatively evaluate with SBS (styrene-butadienestyrene) modified bitumens. For this purpose, bitumen was modified with different polyolefin mixtures (PP:PE) and was also modified with 2%SBS, 4%SBS and 4%PP. To evaluate the effects of polymers on pure bitumen, viscosity, softening point, penetration, temperature susceptibility and mixing-compaction temperature values of all bituminous binders were detected. The test results at 135°C showed that, the viscosities of 3:1 PP:PE and 1:3 PP:PE modified bitumens were higher than the viscosities of 2%SBS and 4%PP modified bitumens. It was seen that, 4%SBS modified bitumen was the binder with the lowest temperature sensitivity and the highest viscosity at 135°C. It was detected that the viscosities of all binders at 135°C did not exceed the 3 Pa s specification criterion. It was determined that, 3:1 PP:PE modified bitumen was a binder with a lower temperature sensitivity than other polyolefin modified bitumens and 2%SBS modified bitumen. Results showed that 2%SBS modified bitumen was the binder with the lowest mixing-compaction temperatures among all of the polymer modified binders. [ABSTRACT FROM AUTHOR]

The total mass of individual synthetic polymers present as microplastic (MP < 2 mm) pollutants in the sediments of interconnected aquatic environments was determined adopting the Polymer Identification and Specific Analysis (PISA) procedure. The investigated area includes a coastal lakebed (Massaciuccoli), a coastal seabed (Serchio River estuarine), and a sandy beach (Lecciona), all within a natural park area in Tuscany (Italy). Polyolefins, poly(styrene) (PS), poly(vinyl chloride) (PVC), polycarbonate (PC), poly(ethylene terephthalate) (PET), and the polyamides poly(caprolactame) (Nylon 6) and poly(hexamethylene adipamide) (Nylon 6,6) were fractionated and quantified through a sequence of selective solvent extractions followed by either analytical pyrolysis or reversed-phase HPLC analysis of the products of hydrolytic depolymerizations under acidic and alkaline conditions. The highest concentrations of polyolefins (highly degraded, up to 864 µg/kg of dry sediment) and PS (up to 1138 µg/kg) MPs were found in the beach dune sector, where larger plastic debris are not removed by the cyclic swash action and are thus prone to further aging and fragmentation. Surprisingly, low concentrations of less degraded polyolefins (around 30 µg/kg) were found throughout the transect zones of the beach. Positive correlation was found between polar polymers (PVC, PC) and phthalates, most likely absorbed from polluted environments. PET and nylons above their respective LOQ values were found in the lakebed and estuarine seabed hot spots. The pollution levels suggest a significant contribution from riverine and canalized surface waters collecting urban (treated) wastewaters and waters from Serchio River and the much larger Arno River aquifers, characterized by a high anthropogenic pressure. [ABSTRACT FROM AUTHOR]

While surface segregation has been intensively studied in thin films, relatively little has been investigated in filament geometries. In contrast to thin films, the filament surface forms a continuum, with interactions both at the free air and internal filament interface, which makes it difficult to achieve an equilibrium configuration. This asymmetry has become particularly apparent with the increasing use of additive manufacturing where entire structures are constructed via layered deposition of filamentous layers from a moving thermal nozzle. In addition, this process is highly non-equilibrated with poor thermal retention and is responsible for insufficient filament–filament interfacial fusion and internal pore formation along the printing direction. These features all contribute to poor mechanical and structural properties, which are exacerbated in semi-crystalline polymers, such as Polylactic Acid (PLA), where the melting point, Tm, is much higher than the glass transition, Tg. Even though system is liquid the molecules become ordered within the crystal structure and this ordering interferes with interdiffusion, which in turn prevents proper interfacial fusion. Capitalizing on the differential in surface tension, we show that addition of less than 1%, or trace amounts, of longer chain polymers, an oriented core shell structure, will be formed with a self-limiting thickness of three time the radius of gyration, Rg, of the tracer chains. The lower Tg of the tracers and their orientation makes them poised for interdiffusion when subsequent layers are deposited producing structures with significant improvement of the mechanical properties and internal structural integrity.

Objectives: This work aimed to evaluate and compare the surface roughness, contact angle, and C. albicans adhesion in three materials for removable denture bases: polymethylmethacrylate and the thermoplastic resins polypropylene and polyolefin. Methods: Nine samples were manufactured, three of each material (n=3): polypropylene, polyolefin, and polymethylmethacrylate (control group). The thermoplastic resins were fabricated by injection technique and the polymethylmethacrylate by compression technique. After laboratory polishing, the surface roughness (Ra and Rz) was assessed with the 3D optical roughness meter NPFLEX, and the contact angle was measured with the optical tensiometer Contact angle system OCA15. C. albicans adhesion was assessed through colony- forming unit assays (n=9). ANOVA and Kruskal-Wallis tests were done to compare groups, considering a significance level of 0.05. Results: All values obtained for the control group were lower than those obtained for the thermoplastic resins. Statistically significant differences were found: for Ra between polypropylene (0.15±0.072 μm) and polymethylmethacrylate (0.03±0.006 μm) (p=0.045); for the contact angle between the three groups (p