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Multilayer flexible food packaging is under pressure to redesign for recyclability. Most multilayer films are not sorted and recycled with the currently available infrastructure, which is based on mechanical recycling in most countries. Up to now, multilayer flexible food packaging was highly customizable. Diverse polymers and non-polymeric layers allowed a long product shelf-life and an optimized material efficiency. The need for more recyclable solutions asks for a reduction in the choice of material. Prospectively, there is a strong tendency that multilayer flexible barrier packaging should be based on polyolefins and a few recyclable barrier layers, such as aluminium oxide (AlOx) and silicon oxide (SiOx). The use of ethylene vinyl alcohol (EVOH) and metallization could be more restricted in the future, as popular Design for Recycling Guidelines have recently reduced the maximum tolerable content of barrier materials in polyolefin packaging. The substitution of non-recyclable flexible barrier packaging is challenging because only a limited number of barriers are available. In the worst case, the restriction on material choice could result in a higher environmental burden through a shortened food shelf-life and increased packaging weights.

Rechargeable lithium-ion batteries (LIBs) have emerged as a key technology to meet the demand for electric vehicles, energy storage systems, and portable electronics. In LIBs, a permeable porous membrane (separator) is an essential component located between positive and negative electrodes to prevent physical contact between the two electrodes and transfer lithium ions. Among several types, microporous polyolefin membranes have dominated the commercial separator market for LIBs operated with liquid electrolytes, favored for their chemical and electrochemical stability, high mechanical strength, uniform pore size, and inexpensive manufacturing and materials cost. In this review, we summarize the principles and theoretical background underlying conventional manufacturing processes and newly emerging microporous polyolefin separators. Based on their mechanical and physical properties, as collected from the literature, we introduce a number of processing type-dependent characteristics and universal correlations among their properties. This will provide a macroscopic view on the subject and a guideline for the development of next-generation separators.

The effects of process conditions and their interactions on the catalyst activity in 1-hexene polymerization were studied with design of experiments by response surface methodology (RSM) using a commercial Ziegler-Natta (ZN) catalyst in the form of TiCl4/MgCl2/Di-n-butyl phthalate. The effect of different operational variables on the catalyst activity was examined by performing the primary experiments of 1-hexene polymerization. Among different operational variables, three variables including monomer concentration, polymerization temperature and cocatalyst/catalyst molar ratio (Al/Ti) were considered as the main parameters which affected the catalyst activity in the 1-hexene polymerization. The Box-Behnken model with three main parameters in three level responses for each factor was applied to analyze the parameter relationships. After demonstrating the reproducibility of the experimental results, the statistical analysis of experimental data showed that the monomer concentration and Al/Ti molar ratio affected the catalyst activity significantly. It was found that, at room temperature, by increasing the monomer concentration from 80.0 mmol to 239.9 mmol, the activity of the studied ZN catalyst increased from 75.2 to 265.1 gpoly(1-hexene)/gcat. In addition, by changing the Al/Ti ratio from 45.9 to 136.8, the catalyst activity increased from 145.2 to 265.1 gpoly(1-hexene)/gcat. The maximum activity of catalyst was obtained at the polymerization temperature around 25°C, and by increasing the temperature the activity of studied catalyst decreased. Based on the RSM, the best polymerization condition was obtained at a polymerization temperature of about 35°C, Al/Ti ratio of 136.8, and monomer concentration of 239.9 mmol, which resulted in maximum productivity of the catalyst.

The current efforts in moving closer towards a circular plastics economy puts massive pressure on recycled plastics, especially recycled polyethylene (rPE) and recycled polypropylene (rPP) to enter new markets. Their market penetration remained low so far, despite PE and PP constituting the largest share of plastic wastes. However, with the current imperative of more circularity comes a new focus on performance of recyclates. Hence, a detailed understanding of composition and structure–property relationships of post-consumer recyclates has to be developed. Five recycling companies from the Austrian and German markets were asked to supply their purest high-quality rPE and rPP grades. These were characterized by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy, and micro-imaging. Technological characterization included density measurements, determination of the melt flow rate (MFR), and Charpy impact testing. All recyclates contained diverse contaminants and inclusions ranging from legacy fillers like calcium carbonate to polymeric contaminants like polyamides or polyolefin cross-contamination. The overall amount, size, and distribution of contaminants varied significantly among suppliers. Furthermore, first structure–property relationships for polyolefin recyclates that link inorganic content and polymeric purity with density and impact performance could be derived.

In this study, one of the higher Poly α-olefins, poly1-hexene (PHex), was rationalized for possible application in in-vitro drug delivery system. In this aspect, PHex was synthesized using a conventional TiCl4/MgCl2/TEAL Ziegler-Natta catalyst. The synthesized polymer was characterized by NMR, GPC, and cellular toxicity methods. Then, the effect of triethylcitrate and glycerin plasticizers on the topography, water vapor permeation and water sorption properties of the prepared fabricates was investigated. Finally, in-vitro drug release characteristic of the gentamicin loaded PHex and PHex/TEC samples was evaluated during eight days. Obtained results highlighted the potential of PHex elastomer in developing medical devices with enhanced drug release characteristics. [ABSTRACT FROM AUTHOR]

The purpose of this study is to provide a theoretical mechanism during the degradation of polyolefin plastic waste using phytochemicals. Existing degradation (physical, chemical and biological) methods are ineffective, expensive and notably time consuming during the degradation of polyolefin plastics. During the phytochemical degradation process, initially, polyolefin plastic is oxidized and converted into the hydrophilic nature by photo-oxidation. Thereafter, phyto phenols can be used to cleave the main chains of polyolefin plastics, thereby, small molecular hydrocarbons are formed such as oligomers, monomers and dimers. During this process, primary products like all the reactive hydroperoxides and free radicals might be produced and lead to further chain cleavage via peroxide cross linkage. Besides, the consequences of plastic chain cleavage make the product apparently more susceptible to biodegradation. The phytochemical based degradation mechanism is useful for the researchers in the direction towards plastic hazards reduction and management on the earth's environment. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department 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.)

The glass transition temperature, dynamic fragilities, and flow activation energy of a series of well‐entangled poly(α‐olefin) (PαO) molecular bottlebrushes were measured as a function of side chain length (Nsc). The PαO bottlebrushes studied here have side chain lengths, Nsc, ranging from 4 (poly(1‐hexene)) to 10 (poly(1‐dodecene). A linear polyolefin (polypropylene), with Nsc = 1, was included in this study as a reference. The observed glassy dynamics behavior in the PαO bottlebrushes is opposite to that observed in linear polymers, namely, the glass transition temperature, the dynamic fragility, and the activation energy of structural relaxation are decreasing functions of the backbone rigidity. This anomalous behavior is due to a decrease in correlation between adjacent backbones, which is directly related to their cooperativity in the α‐relaxation, as Nsc and the concomitant distance between backbones increase. This change in conformation is also manifested as an increase in free volume and the consequent decrease in monomeric friction coefficient. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1293–1299 [ABSTRACT FROM AUTHOR]

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

In this study, the properties of virgin linear low-density polyethylene (LLDPE) and its blends with reclaimed plastic solid waste (PSW) are investigated by thermogravimetry, differential scanning calorimetry (DSC), infrared spectroscopy and scanning electron microscopy (SEM). The PSW constituted polyolefin (PO) polymers recycled mechanically via extrusion/blown-film and exposed to accelerated weathering tests to determine the change in their degradation behaviour. The oxidation products determined using the FTIR analysis and thermal stability studies points toward the blend constituting 25% of waste by weight as the most stable. Changes in crystallinity of the polymers were attributed to the crystal size change as a consequence of the weathering mechanism. The DSC results revealed that both oxidation induction temperature (OIT) and crystallinity were affected by the PO waste content. This points towards the impact of polymers immiscibility and polydispersity within the matrix of the blends due to chain scission reaction and oxidation with the UV exposure. [ABSTRACT FROM AUTHOR]

One of the most used carbonaceous materials by industry are carbon blacks, which have technological applications in polymeric composites, coatings and paints, electric and electrochemical devices. One drawback is that they are produced from fossil fuels. Although biochars are also carbonaceous materials some disadvantages like their larger particles size, high ash content and highly oxygenated surface must be overcome to enable their use as substitute of carbon blacks in composites. Sugarcane bagasse biochar was used to produce carbonaceous materials to substitute carbon blacks. Milling of biochar decreased particle size from several hundreds of micrometers to 100–500 nm and narrowed its size distribution. Chemical leaching reduced the inorganic compounds and ash content by almost 20%. Great advance was achieved when biochar was thermally annealed in alcohol vapor atmosphere which resulted in biochar-based material with very low oxygenated carbon species at particles surface and turned them hydrophobic. Almost no C–O/C=O and O–C=O peaks components were observed at the X-ray photoelectron spectroscopy spectrum. Reactive thermal annealing of the biochar based additive was a key procedure to obtain polyethylene composites (5% loading) with mechanical, thermal and colorimetric properties very close to the ones prepared with the carbon black from fossil fuels. [ABSTRACT FROM AUTHOR]

For design of gas phase polymerization processes for propylene copolymers, it is essential to understand how monomer solubility and diffusivity in the polymer are affected by comonomer content and polymer crystallinity. Measurements of solubilities and diffusion coefficients of ethylene in four propylene-based (ethylene and 1-butene) copolymer (cPP) samples are reported with a gravimetric method at temperatures below and above the melting point temperatures of each cPP. Diffusion coefficients were correlated with free-volume-theory adopting the free volume fraction evaluated from PVT data and the glass transition temperature of polymer. In the polymer rubbery state, solubilities and diffusion coefficients of ethylene could be predicted with the cPP crystallinities and FVT parameters obtained from molten state data. Image 1 • Solubility and diffusivity data of ethylene in four propylene copolymers. • Solubility prediction with molten state data and crystallinity. • Diffusivity prediction with free-volume theory and crystallinity. [ABSTRACT FROM AUTHOR]

The use of polyolefins in structural components requires the simultaneous improvement of stiffness and toughness of the matrix, whilst in the case of sensing components during operation, additional functions are needed such as electrical conductivity. However, providing various desired properties without impairing those intrinsic to the materials can be somewhat challenging. In this study we report the preparation of an isotactic polypropylene (iPP)/styrene-ethylene-butylene-styrene triblock copolymer (SEBS)/graphene system that combines enhanced mechanical properties with electrical conductivity. Blends were prepared by solution mixing (SoM) and solution/solid state mixing (SoM/SSM) formulation routes prior to melt processing. The nanocomposites were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and the electrical and mechanical properties were evaluated. The materials prepared via the SoM/SSM route displayed good electrical conductivity while retaining the mechanical properties of iPP, making them attractive materials for low cost and high throughput structural components with sensing capacity. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials 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.)

Introduction: Stable distal radius fractures in children are frequently treated by immobilisation with a cast and heal readily without complications. This randomised clinical trial aimed to assess patient satisfaction and casting-related clinical outcomes when using polyolefin cast, a new cast material, compared to the conventional fibreglass cast.Methods: A total of 80 patients (age range 7-16 years) with radiograph-confirmed stable distal radius fractures were recruited. They were randomised to either the fibreglass group or polyolefin group, with short arm cast immobilisation for 20-30 days. After cast removal, the incidence of skin rash, growth of hair and cast breakage was recorded along with the administration of patient satisfaction questionnaires. Mann-Whitney U test or Fisher's exact test was applied to compare results.Results: Overall, 34 patients from the fibreglass group and 31 patients from the polyolefin group were included in the final analysis. Significantly fewer patients from the polyolefin group reported itchiness during the casting period (p = 0.038). However, significantly more cast breakages were observed for the polyolefin group in the palmar bar region (p = 0.009). Patients from the polyolefin group were overall more satisfied (fibreglass group = 3.15/5 vs. polyolefin group = 3.74/5; p = 0.002).Conclusion: Polyolefin cast reduces itchiness during casting and provides higher overall patient satisfaction during the treatment of stable distal radius fractures in children in tropical climates. However, patients should be counselled regarding potential cast breakage, which did not compromise safety, and the higher costs involved. [ABSTRACT FROM AUTHOR]

This work provides evidence that ultra-stable Y zeolite (USY) and HZSM-5 zeolites were active as catalysts for the pyrolysis of urban plastic wastes, decreasing its degradation temperature. When HZSM-5 was used as the catalyst, at 450 °C and 30 min, an increase in the solid fraction and a reduction in the liquid fraction were observed. On the other hand, the best catalytic cracking performance was observed for the reaction catalyzed by USY zeolite, and a higher amount of liquid fraction was obtained. Moreover, the increase of reaction time and temperature was favorable to obtain better results in thermal pyrolysis. As to the liquid fraction composition, its components were alkylbenzenes, olefins, and naphthalenes in the thermal pyrolysis whereas alkylbenzenes were the main component in the HZSM-5-catalysed pyrolysis and that catalyzed by USY provides higher amounts of olefins.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Highlights • Prosopis juliflora was liquefied with Polyolefin waste for bio-oil production. • Hydrothermal liquefaction produced 61.23%wt of bio-oil. • Bio-oil had 88.23% purity (petro-diesel) with 78% energy recovery efficiency. • HTL wastewater had low weight acids, suggests effective reusability. Abstract In this study, co-liquefaction (HTL) of Prosopis juliflora (PJ) biomass with polyolefin waste (PO) was performed to produce bio-oil. HTL on bio-oil yield was studied at varying PJ to PO ratios (0:1, 1:0, 1:1, 2:1, 3:1, 4:1 and 5:1) and temperatures from 340 to 440 °C. Bio-oil and HTL by-products were characterized by Mass Spectroscopy (GC–MS) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Bio-oil yield was around 61.23%wt at 420 °C for 3:1 blends with 3 wt% of HCl activated bentonite catalyst at 60 min holding time. HHV value was 46 MJ/Kg with 88.23% purity (petro-diesel). Additionally gas possessed 26.28% of Hydrogen gas, 45.59% of Carbon dioxide gas, 7.1% of Carbon monoxide gas, 8.12% of Methane gas and other elements. The energy recovery (78%) and carbon recovery (94%) was higher for 3:1 blends bio-oil than PO and PJ processed bio-oils. HTL wastewater possessed higher degree of reusability nature as HTL medium. [ABSTRACT FROM AUTHOR]

Abstract Microplastics are new pollutants considered a source of concern for the oceans worldwide. This research reports the concentrations of trace metals on microplastics collected on beaches from Cartagena, an industrialized city in the Caribbean. Mercury (Hg) was quantified using a Hg analyzer and forty-seven trace elements were assessed by ICP/MS. Most abundant microplastics in beaches were those with the lower degree of surface degradation features (SDF), categorized as white-new polyethylene pellets, followed by secondary microplastics (SM). Greater Hg levels were found in SM, white-degraded (WDP) and black pellets. Trace elements concentrations were linked to the degree of SDF registered in examined pellets, with larger concentrations in WDP. Compared to white-new pellets, Ba, Cr, Rb, Sr, Ce, Zr, Ni, Pb were the most accumulated elements in WDP, as their surface enhance the sorption processes. Microplastic pollution represents a toxicological hazard because its ability to accumulate and transport toxic elements. Highlights • Trace elements in beached microplastics were evaluated in Cartagena, a Caribbean city. • Most microplastics were white-new polyethylene pellets and secondary microplastics. • Greater Hg levels found in secondary microplastics, white-degraded and black pellets. • Trace elements concentrations were linked to the degree of pellet degradation. • Barium, Cr, Rb, Sr, Ce, Zr, Ni, Pb, among others, accumulated in degraded pellets. [ABSTRACT FROM AUTHOR]

Abstract Waste polyethylene (PE) was pyrolyzed in a continuous two-stage pyrolysis process having auger and fluidized bed reactors. The main aim of the study was to produce a pyrolysis gas containing high contents of olefins along with a clean pyrolysis oil at moderate reaction conditions. In the experiment, the temperatures of the auger and fluidized bed reactors were varied from 30 to 300 °C and from 653 to 736 °C, and a CaO hot filter was used to capture HCl liberated during pyrolysis. At elevated auger reactor temperatures, the PE molecules in the reactor shifted to higher vibrational energy states, resulting in the weakening of the C C bond of PE molecule. The PE melt leaving the auger reactor could finally be decomposed into short chains in the fluidized bed reactor. The total yield of ethene, propene, and 1,3-butadiene was 30–53 wt.%. The olefin yield increased with increasing auger reactor temperature. The highest gas (74.6 wt.%) and ethene (34.5 wt.%) yields were obtained when N 2 was used as the fluidizing medium. Pyrolysis oil, whose yield was 15–38 wt.%, was mostly composed of aromatic hydrocarbons. The CaO hot filter could reduce the chlorine content in the pyrolysis oil to 66.5 ppm. Highlights • A continuous two-stage pyrolysis of waste PE was successfully conducted. • The two-stage pyrolysis process revealed different characteristics than one-stage. • Pyrolysis gas increased olefin yield at higher temperature of auger reactor. • The total yield of ethene, propene, and 1,3-butadienes was maximized at 53 wt.%. • A pyrolysis oil having 66.5 ppm chlorine could be obtained with a CaO hot filter. [ABSTRACT FROM AUTHOR]

Olefin polymerization catalysts employing late transition metals, such as Ni, Pd, Fe and Co, have been heavily investigated since their discovery in the mid‐1990s. Despite the advantages and appeal these catalysts have displayed in academic research, their implementation in industry has remained restricted due to a variety of limitations and drawbacks. One specific limitation is the relative thermal instability of most late transition metal olefin polymerization catalysts at the temperatures commonly utilized for industrial polymerizations. This review focuses on the development of Ni‐, Pd‐, Fe‐ and Co‐based olefin polymerization catalysts that display increased thermal stability at super‐ambient reaction temperatures. These advances in thermal stability have been realized using a variety of ligand modifications, and their polymerization activities and thermal stability are summarized herein. Lastly, a brief outlook on the future of thermally stable, late transition metal olefin polymerization catalysts is provided. © 2018 Society of Chemical Industry This review focuses on the development of Ni‐, Pd‐, Fe‐ and Co‐based olefin polymerization catalysts that display enhanced thermal stability at super‐ambient reaction temperatures. [ABSTRACT FROM AUTHOR]

The behaviors of three different catalyst systems, TiCl4/MgCl2, Cp2ZrCl2 and Cp2HfCl2, were investigated in ethylene/1,5‐hexadiene copolymerization. In the Fourier transform infrared spectra of the copolymers, cyclization and branching were detected for 1,5‐hexadiene insertion in the metallocene and Ziegler–Natta systems, respectively. DSC and viscometry analyses results revealed that copolymers with lower Tm and crystallinity and higher molecular weight were obtained with metallocene catalysts. The sequence length distribution of the copolymers was investigated by using the successive self‐nucleation and annealing thermal fractionation technique. The continuous melting endotherms obtained from successive self‐nucleation and annealing analysis were employed to get information about short‐chain branching, the branching dispersity index, comonomer content and lamella thickness in the synthesized copolymers. The results established that metallocene catalysts were much more effective than Ziegler–Natta catalysts in the incorporation of 1,5‐hexadiene in the polyethylene structure. Metallocene‐based copolymers had higher short‐chain branching and comonomer content, narrower branching dispersity index and thinner lamellae. Finally, the tendency of the employed catalysts in the 1,5‐hexadiene incorporation and cyclization reaction was explored via molecular simulation. The energy results demonstrated that, in comparison to Ziegler–Natta, metallocene catalysts have a much higher tendency to 1,5‐hexadiene incorporation and cyclization. © 2018 Society of Chemical Industry Ethylene/1,5‐hexadiene were copolymerized using conventional Ziegler–Natta, zirconocene and hafnocene catalysts. Analyses of the products revealed that metallocene‐based copolymers contain a higher comonomer amount in C5‐ring form while branching was the dominant mechanism in the Ziegler–Natta case. The capability of the studied catalysts in the 1,5‐hexadiene incorporation and cyclization reaction was compared quantitatively by molecular simulation which confirmed the experimental data. [ABSTRACT FROM AUTHOR]

The preparation of multilayered structures has been thought as a complicated process until our recent study illustrating an effective method through high speed thin wall injection molding (HSTWIM) of polypropylene (PP) and polyethylene (PE) based blends. Current study investigates the effect of blends composition as well as the addition of carbon nanotubes (CNT) on the structure and properties of these blends. It is observed that a close ratio of high density polyethylene (HDPE) and impact copolymer polypropylene (ICP) triggers the formation of a multilayered structure. Meanwhile, PE is migrated into the rubber phase in ICP, leading to the distribution of some rubber phase on the interface between PP and PE, which is thought as beneficial for the interfacial interaction. Meanwhile, epitaxial growth of PE crystals on PP substrate is also observed. The presence of rubber phase on the interface, multilayered structure and epitaxial growth of PE crystals on PP are thought to be responsible for the observed mechanical enhancement in tensile strength as well as strain at break. Furthermore, the addition of CNTs leads to enhanced strength, reduced strain at break and anisotropic conductive network. [ABSTRACT FROM AUTHOR]

Lignosulfonate is a cheap material available in large quantities obtained as a byproduct of paper and cellulose. In this work, blends of polypropylene (PP) and sodium lignosulfonate (LGNa) were developed to evaluate the potential use of lignosulfonate as a lightweight, thermal insulation and flame retardant material. The blends were obtained by mixing in a torque rheometer and molded after compression. The blend proprieties were evaluated by physical, morphological, thermal, thermal conductivity, and flammability tests. The measured values were compared with theoretical models. The results indicated that a heterogeneous blend with a higher number of separated domains is formed when the LGNa content increases from 10 to 40 wt%. In addition, the density and thermal conductivity coefficient of the blends studied are not affected by the addition of LGNa. However, when the LGNa content in the blend exceeds 20 wt% the thermal stability and flame retardant proprieties are considerably reduced. The theoretical models based on the rule of mixtures showed a good agreement with the experimental values obtained from blend density, thermal conductivity, and thermal stability. In general, lignosulfonate tested in this work shows potential to be used as a reactive component in polymer blends.

High pressure phase behavior measurements were done for thirty-two polyolefins in 2-methylpentane, n -pentane, and n -hexane to systematically map out the liquid-liquid equilibrium (LLE) boundaries for commercial polyolefins in hydrocarbon solvents. The samples cover two decades of molecular weight range, and contain varying levels of propylene, 1-butene, 1-hexene, and 1-octene. All samples had M w / M n < 1.30. Samples with adequate crystallinity were confirmed to have unimodal chemical composition distributions by TREF. The data were fit to SAFT-HR, SAFT-1, and PC-SAFT using temperature independent polyethylene-solvent and side branch-solvent interaction parameters. SAFT-HR and SAFT-1 adequately fit the data after modifying the literature polyethylene SAFT parameters. PC-SAFT fits the data less well because it predicts an excessively steep slope in the pressure-temperature LLE boundaries. [Display omitted] • Lower critical solution temperature of polyolefins in hydrocarbon solvents. • Lower critical solution temperature of polyolefins in 2-methylpentane. • SAFT, SAFT-1, and PC-SAFT modeling of polyolefins in hydrocarbon solvents. • Liquid-liquid equilibrium of polyolefins in hydrocarbon solvents. • Molecular weight and composition distribution effects on the lower critical solution temperature. [ABSTRACT FROM AUTHOR]

The huge scale of plastic waste generation and its environmental consequences drive the demands for catalytic plastic upcycling processes. Here, we report efficient polypropylene (PP) hydro-conversion over Ru and Ni supported on a sol-gel anatase TiO 2 (TiO 2 -A-SG). A small number of Brønsted acid sites on TiO 2 -A-SG enables hydrocracking, improving efficiency, steering the selectivity towards high-valued C 4–20 , and allowing more isomerization, compared to Ru-based monofunctional hydrogenolysis catalysts. The relative contribution of hydrocracking increases with lower hydrogen partial pressure, more branched substrates, and lower Ru loading. Ni/TiO 2 -A-SG exhibits superior hydrocracking activity and selectivity to Ni on conventional Brønsted-acidic supports, particularly zeolites. Mechanistic studies shows fast isomerization and sequential β -scissions caused by strong polymer-catalyst interaction and fast cracking with abundant 3C. This favors C 4–12 formation and prevents secondary reactions. This work demonstrated a novel, highly efficient noble-metal-free catalyst for plastic waste upcycling, while advancing the mechanistic understanding of polyolefin hydro-conversion. [Display omitted] • Low-population Brønsted-acid sites on M/TiO 2 -A-SG catalyzing PO hydrocracking. • Hydrocracking improving efficiency and selectivity over Ru-catalyzed hydrogenolysis. • High P H2 and substrate branching level favoring hydrocracking over hydrogenolysis. • TiO 2 -A-SG more efficient in PO hydrocracking than SiO 2 -Al 2 O 3 -based supports. • Strong adhesion of polymers affecting the product selectivity and mechanisms. [ABSTRACT FROM AUTHOR]

This paper investigated the structure, microwave dielectric properties and thermal properties of xZn 0.15 Nb 0.3 Ti 0.55 O 2 @VTMS/polyolefin composites in the range of x = 83–91 wt%. Zn 0.15 Nb 0.3 Ti 0.55 O 2 (ZNT) powder underwent conventional sintering process before being laminated with 1,2-PB/EPDM/SBS through hot-press process after being modified by Vinyltrimethoxysilane (VTMS). In this study, we analyzed the surface character, microstructure, microwave dielectric properties and thermal performances of the composite material. The findings indicate that a core-shell structure was formed to enhance the compatibility between ceramic particles and polyolefin matrix. Furthermore, the modified ceramic formed an interfacial layer with resin matrix that limited the movement of resin chain segments and improved the thermal stability of the composites. However, further increase of ceramic content more ceramic agglomerates and pores introduced more ceramic agglomerates and pores resulting in reduced cross-linking density of the resin. Consequently, a high-D k composite was obtained when x = 89 wt% at 10 GHz: D k = 16.79, D f = 0.0023 and τ ε = −120 ppm/℃, which is promising for microwave applications. • Zn 0.15 Nb 0.3 Ti 0.55 O 2 was coated by VTMS and laminated with polyolefin (1,2-PB/EPDM/SBS) by hot-press process. • The composite exhibits a high D k of 16.79, small D f of 0.0023 and low τ ε of − 120 ppm/℃. • Ceramic fillers hinder the movement of resin chain segments and improved the thermal stability of the composites. • Introducing ceramic fillers reduces cross-link density of the composite. [ABSTRACT FROM AUTHOR]

Due to easy availability of cheaper raw material and increase in new applications, the use of polyolefins in various industries is becoming a major priority. The Middle East region, on account of its vast oil and gas reserves has, in the last decade or so, been developing many new petrochemical complexes with their expansion into colossal polyolefin production capacities. The predictions are that by 2020 the Middle East region will dominate the polyolefin industry as a whole. Furthermore, with proven oil reserves of about 21.7 thousand million tons (4th world ranking) and natural gas of 34.0 trillion cubic meters (1st world ranking), Iran’s petrochemical industry is supported by diverse and abundant feedstock reserves. In line with other polyolefin producers’ developments in the Middle East, Iran's National Petrochemical Company (NPC) has undergone massive structural and technological transformations in the last two decades in order to set up ambitious plans for further capacity increase and native technology developments. This article mainly focuses on Iran today’s position and its future plans in the polyolefins industry.

The key to the preparation of polymer nanocomposites with new or improved properties resides in the homogeneous dispersion of the filler and in the efficient load transfer between components through strong filler/polymer interfacial interactions. This paper reports on the preparation of a series of nanocomposites of graphene and a polyolefin using different experimental approaches, with the final goal of obtaining multifunctional materials. A high-density polyethylene (HDPE) is employed as the matrix, while unmodified and chemically modified graphene fillers are used. By selecting the correct combination as well as the adequate preparation process, the nanocomposites display optimized thermal and mechanical properties, while also conferring good gas barrier properties and significant levels of electrical conductivity.

Polyolefin geosynthetics are susceptible to oxidative degradation, which in turn leads to diminished mechanical properties in geotechnical constructions. When using these materials, it is extremely important to determine their durability over time in particularly aggressive conditions. In order to prolong the life of a geosynthetic material, antioxidants are added during the manufacturing process. The function of antioxidants is to prevent polymer oxidation reaction in time. As the antioxidant content is depleted, the polymer becomes less protected towards oxidative attacks. This article describes the aging process of uniaxial (high density polyethylene) HDPE geogrids under the influence of chemical and environmental factors. Evaluations of accelerated aging test of the uniaxial HDPE geogrids were incubated in simulated landfill conditions for a period of 12 months. Three temperatures (25 °C, 45 °C, and 75 °C) were selected for carrying out the aging experiments in aqueous solutions mimicking landfill conditions. The changes observed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and melt flow index (MFI) correlate with the mechanical properties of the aged geogrid. No significant changes in the FTIR and MFI were observed over the 12 months of accelerated aging tests at none of the three different temperatures. The oxidation induction time (OIT) test showed no antioxidant remaining in the geogrid following eight months of aging test at 75 °C. No significant changes in the influence of accelerated aging tests on the average relative elongation at 25 °C and 45 °C of the tested material were observed. Accelerated aging tests at 75 °C showed that the mean elongation of 12.12% for the sample not subjected to accelerated aging tests (new sample) increased to 19.32% (after 12 months of incubation).

The pyridylamido hafnium complex (I) discovered at Dow is a flagship catalyst among postmetallocenes, which are used in the polyolefin industry for PO-chain growth from a chain transfer agent, dialkylzinc. In the present work, with the aim to block a possible deactivation process in prototype compound I, the corresponding derivatives were prepared. A series of pyridylamido Hf complexes were prepared by replacing the 2,6-diisopropylphenylamido part in I with various 2,6-R2C6H3N-moieties (R = cycloheptyl, cyclohexyl, cyclopentyl, 3-pentyl, ethyl, or Ph) or by replacing 2-iPrC6H4C(H)- in I with the simple PhC(H)-moiety. The isopropyl substituent in the 2-iPrC6H4C(H)-moiety influences not only the geometry of the structures (revealed by X-ray crystallography), but also catalytic performance. In the complexes bearing the 2-iPrC6H4C(H)-moiety, the chelation framework forms a plane; however, this framework is distorted in the complexes containing the PhC(H)-moiety. The ability to incorporate α-olefin decreased upon replacing 2-iPrC6H4C(H)-with the PhC(H)-moiety. The complexes carrying the 2,6-di(cycloheptyl)phenylamido or 2,6-di(cyclohexyl)phenylamido moiety (replacing the 2,6-diisopropylphenylamido part in I) showed somewhat higher activity with greater longevity than did prototype catalyst I.

Polyolefins (POs) are the most abundant polymers. However, synthesis of PO-based block copolymers has only rarely been achieved. We aimed to synthesize various PO-based block copolymers by coordinative chain transfer polymerization (CCTP) followed by anionic polymerization in one-pot via conversion of the CCTP product (polyolefinyl)2Zn to polyolefinyl-Li. The addition of 2 equiv t-BuLi to (1-octyl)2Zn (a model compound of (polyolefinyl)2Zn) and selective removal or decomposition of (tBu)2Zn by evacuation or heating at 130 °C afforded 1-octyl-Li. Attempts to convert (polyolefinyl)2Zn to polyolefinyl-Li were unsuccessful. However, polystyrene (PS) chains were efficiently grown from (polyolefinyl)2Zn; the addition of styrene monomers after treatment with t-BuLi and pentamethyldiethylenetriamine (PMDTA) in the presence of residual olefin monomers afforded PO-block-PSs. Organolithium species that might be generated in the pot of t-BuLi, PMDTA, and olefin monomers, i.e., [Me2NCH2CH2N(Me)CH2CH2N(Me)CH2Li, Me2NCH2CH2N(Me)Li·(PMDTA), pentylallyl-Li⋅(PMDTA)], as well as PhLi⋅(PMDTA), were screened as initiators to grow PS chains from (1-hexyl)2Zn, as well as from (polyolefinyl)2Zn. Pentylallyl-Li⋅(PMDTA) was the best initiator. The Mn values increased substantially after the styrene polymerization with some generation of homo-PSs (27−29%). The Mn values of the extracted homo-PS suggested that PS chains were grown mainly from polyolefinyl groups in [(polyolefinyl)2(pentylallyl)Zn]−[Li⋅(PMDTA)]+ formed by pentylallyl-Li⋅(PMDTA) acting onto (polyolefinyl)2Zn.