Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

Influence of Electron Beam Irradiation and Coupling Agents on the Thermal Stability of Sugar Cane Bagasse Fiber-Thermoplastics Scrape Composite

The influence of blending of sugar cane bagasse with thermoplastics scrape as well as incorporation of some coupling agents has been conducted using thermogravimetric analysis (TGA). In addition, the effect of electron beam preirradiation of low density polyethylene on the properties of the bagasse-LDPE composite was also studied. Simulation of TGA data reveals that the presence of bagasse fiber accelerates the volatilization of either polypropylene or polyvinylchloride. On the other hand, polyethylene and polystyrene were stable against the heat evolved during the pyrolysis of bagasse fibers. Also, it was found that incorporation of a mixture of pentaerithrol tetraacrylate (PETA) and dicumyl peroxide (DCP) as coupling agents improve the thermal stability of low density polyethylene whereas the role of irradiation was insignificant. Moreover, pronounced enhancement in the thermal stability was detected in polypropylene followed by polystyrene and polyvinylchloride on using PETA.     

Silane grafting and moisture crosslinking of polyethylene: The effect of molecular structure

The silane grafting and moisture crosslinking of different grades of polyethylene have been investigated. Three types of polyethylene (HDPE, LLDPE, and LDPE) with different molecular structures and similar melt flow indices were selected. The initiator was dicumyl peroxide (DCP), and the silane was vinyltrimethoxysilane. The grafting reaction was carried out in an internal mixer. The extent of grafting and the degree of crosslinking were determined, and hot‐set tests were carried out to evaluate the crosslink structure of the different polyethylenes. The LLDPE had the highest degree of grafting, while the LDPE had the least. The rate of crosslinking for LDPE was higher than that of HDPE and LLDPE. The gel content of LDPE was higher than that of HDPE and LLDPE. Hot‐set elongation and the number‐average molecular weight between crosslinks (M_c) were lower for LLDPE and LDPE than for HDPE. Increasing the silane/DCP percentage led to peroxide crosslinking, thereby decreasing the M_c and hot‐set elongation. The number‐average molecular weight (M_n), molecular weight distribution, and number of chain branches were the most important parameters affecting the silane grafting and moisture crosslinking. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

几种热塑性塑料的燃烧行为研究

应用锥形量热仪研究了几种常见热塑性塑料在燃烧过程中的燃烧行为，定量得到聚乙烯（HDPE、LDPE）、聚丙烯、高抗冲聚苯乙烯和聚氯乙烯等在不同入射热流强度（25kW/m^2、50kW/m^2、75kW/m^2）下的热释放速率、质量损失速率、有效燃烧热和总释放热等燃烧性能参数；分析比较了各热塑性塑料的燃烧行为特性，为火灾预防和材料设计提供了文献资料。     

Compatibilizers for recycling of the plastic mixture wastes. II. The effect of a compatibilizer for binary blends on the properties of ternary blends

In this article, we discuss the effect of a compatibilizer for binary blends on the properties of ternary blends composed of high‐density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS) and poly(vinyl chloride) (PVC) virgin polymers with a simulated waste plastics fraction. Chlorinated polyethylene (CPE), ethylene–propylene rubber (EPR), and their 1/1 (w/w) mixture were tested as compatibilizers for the HDPE/PP/PVC ternary blend. CPE, styrene‐ethylene‐propylene block copolymer (SEP), or their 1/1 (w/w) mixture were tested as compatibilizers for the HDPE/PS/PVC ternary blend. The composition of the ternary blends were fixed at 8/1/1 by weight ratio. The amount of the compatibilizer was 3 phr. Rheological, mechanical, and thermal properties were measured. For the 8/1/1 HDPE/PP/PVC ternary blends, the tensile strength was slightly decreased, but the impact strength was significantly increased by adding EPR, CPE, or their mixture. EPR exhibited the most significant impact modification effect for the ternary blends. In a similar way, for 8/1/1 HDPE/PS/PVC ternary blends, on adding SEP, CPE, or their mixture, the tensile strength was slightly decreased, but the impact strength was noticeably increased. It was found that the SEP worked much better as an impact modifier for the ternary blends than CPE or the SEP/CPE mixture did. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1048–1053, 2000     

Mitteilungen/Announcements

Mechanical recycling of thermoplastics for high value applications is directly associated with restabilization. The state of the art of processing-, long term heat- and light stabilization of recyclates in different polymers (e.g. PP, PP/EPDM, HDPE, LDPE, PS, PVC and various blends) with examples from packaging, distribution, automotive and construction industry is shown. Because of predamage and impurities, recyclates degrade faster and differently compared with virgin polymers and, therefore, specially designed stabilizer systems are required according to the previous damage, subsequent application and type of polymer. Recommendations for restabilization include combinations of phenolic antioxidants and phosphites as well as HALS compounds or “Recyclostab” stabilizer systems.     

Thermal and mechanical properties of silane‐grafted water crosslinked polyethylene

The effects of linear low density polyethylene (LLDPE) grafting with vinyltrimethoxysilane by different types and contents of peroxide were studied. When grafting silane onto LLDPE, with 0.10 phr of Dicumyl peroxide (DCP) or 0.05 phr content of 2,5‐Dimethyl‐2,5‐di (tert‐butyl‐peroxy)‐hexane (DHBP), it was found that the grafting effect was improved; however, as Di(2‐tert‐butylperoxypropyl ‐(2))‐benzene (DIPP) or excess DHBP was used, LLDPE was supposed to cause self‐crosslinking, which reduced the grafting effect of silane and was invalid in the processing of extrusion. In this study, vinyl trimethoxysilane (VTMS) was grafted onto various polyethylenes (HDPE, LLDPE, and LDPE) using DCP as an initiator in a twin screw extruder. The grafted polyethylenes were able to crosslink utilizing water as the crosslinking agent. The effects of varied crosslinking time on the mechanical properties of the crosslinked polyethylenes were studied. It was found that the HDPE and LLDPE were apt to crosslink during the grafting process and thus decreased the grafting ratio. Multiple melting behavior was observed for crosslinked LDPE and LLDPE. Mechanical and thermal properties of the crosslinked PE are much better than that of uncrosslinked PE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2383–2391, 2005     

Modification of Ethylene Propylene Diene Terpolymer Rubber by Some Thermoplastic Polymers

Abstract

Blends of ethylene propylene diene terpolymer (EPDM) rubber with thermoplastic polyolefins such as low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), high molecular weight polypropylene (PP), and polypropylene random copolymer grade (PP‐R) were prepared by melt mixing. The physico‐mechanical properties, equilibrium swelling in benzene, and aging properties of the binary blends were investigated, analyzing the effect of the rubber/thermoplastics ratio and the type of the thermoplastic material on these properties. The data obtained indicate that EPDM/PP‐R blend in 20/80 w/w% shows the highest physico‐mechanical properties with improved retained tensile strength at 90°C for 7 days. This blend ratio also gives excellent retained equilibrium swelling in benzene at room temperature for 7 days, although EPDM/LDPE blend in 80/20 w/w% imparts the highest retained elongation at break at 90°C for 7 days.     

Processing and Characterization of Jute Fiber Reinforced Thermoplastic Polymers

Jute fibers were investigated to verify their possible application in reinforcement of thermoplastics. A laboratory press was modified and laminates were produced using polymer films of LDPE, HDPE, PE copolymer, and PP as interlayers. Variations of the processing parameters were carried out in order to find optimal adjustment. High molding temperature leads to a decrease of mechanical properties and water absorption ability of the composites. The effect of water treatment on mechanical properties was also studied.     

Flame retardancy,antifungal efficacies,and physical–mechanical properties for wood/polymer composites containing zinc borate

This work aimed to examine flame retardancy, antifungal performance and physical–mechanical properties for silane‐treated wood–polymer composites (WPCs) containing zinc borate (ZnB). ZnB with content from 0.0 to 7.0 wt% was added to WPCs, and silane‐treated wood contents were varied. The polymers used were poly(vinyl chloride) (PVC) and high‐density polyethylene (HDPE). The decay test was performed according to the European standard EN 113. Loweporus sp., a white‐rot fungus, was used for antifungal performance evaluation. Antifungal performance was observed to decrease with wood content. Incorporation of ZnB at 1.0 wt% significantly increased the antifungal performance of WPCs. ZnB content of greater than 1.0 wt% lowered the antifungal properties of WPCs. The results suggested that the wood/PVC composite exhibited better antifungal performance than the wood/HDPE composite. The addition of wood flour to PVC and HDPE decreased flame retardancy, whereas the incorporation of ZnB retained the flame retardancy. ZnB was found to be more appropriate for wood/PVC than wood/HDPE as a result of hydrogen chloride generated from the dehydrochlorination reaction of PVC. The results indicated that the addition of ZnB did not affect the physical‐mechanical properties of neat polymers and the composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Phase dispersion–crosslinking synergism in binary blends of poly(vinyl chloride) with low‐density polyethylene: Entrapping phenomenon in PVC/LDPE/DCP blend

The co‐crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/low density polyethylene/dicumyl peroxide (PVC/LDPE/DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co‐crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid‐phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/LDPE blends. Meanwhile, the improvement of the tensile properties is dependent mainly on the properties of the LDPE networks. Finally, the mechanism of phase dispersion–crosslinking synergism is presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1296–1303, 2003     

Wood‐thermoplastic composites from wood flour and high‐density polyethylene

High‐density polyethylene/wood flour (HDPE/WF) composites were prepared by a twin‐screw extruder. The effects of WF, silane coupling agents, polymer compatibilizers, and their content on the comprehensive properties of the WF/HDPE composites have been studied in detail, including the mechanical, thermal, and rheological properties and microstructure. The results showed that both silane coupling agents and polymer compatibilizers could improve the interfacial adhesion between WF and HDPE, and further improve the properties of WF/HDPE composites, especially with AX8900 as a compatibilizer giving higher impact strength, and with HDPE‐g‐MAH as a compatibilizer giving the best tensile and flexural properties. The resultant composite has higher strength (tensile strength = 51.03 MPa) and better heat deflection temperature (63.1°C). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical Properties of Polymers Filled with Iron Powder

Mechanical properties of metal-polymer matrix composites were investigated experimentally. High density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS) were used as the polymer matrix and Fe powder in 5, 10, and 15 vol% was used as the metal. The modulus of elasticity, yield and tensile strength, % elongation, Izod notched impact strength, Shore D hardness, and fracture surfaces of the composites were determined. It was found that vol% Fe reduced the Izod impact strength of HDPE much more than that of PP and PS, while Fe powder increased the hardness of HDPE more than that of PP and PS. Among the composites, PS-Fe composites had higher yield, tensile strength and modulus of elasticity than HDPE-Fe and PP-Fe composites. However, % elongation of PS-Fe composites was lower than that of the other composites. In addition, HDPE- and PP-based composites exhibited ductile type fracture, while PS-Fe composites exhibited brittle type fracture.     

Effects of silane and MAPE coupling agents on the properties and interfacial adhesion of wood-filled PVC/LDPE blend

Composite samples were prepared from Poly(vinyl chloride)/low-density polyethylene (PVC/LDPE) blend, compatibilized by PA20 (methyl methacrylate-co-butyl acrylate copolymer), and reinforced by different levels of rubber-wood sawdust. To improve the mechanical properties of the composites, Silane A-137 (Octyltriethoxy silane), Silane A-1100 (γ-aminopropyltriethoxy silane), or MAPE (maleic anhydride-grafted-polyethylene) were introduced. It was found that the additions of Silane A-137, Silane A-1100, and MAPE could improve tensile and impact properties of the composites, regardless of the sawdust contents. Physical or chemical interactions for all coupling agents with the wood-PVC/LDPE composites used were proposed in this work. Silane A-137 or MAPE tended to give better improvement in the mechanical properties of the composites than Silane A-1100, because of the presence of the nonpolar chain ends of Silane A-137 or MAPE molecules. Besides, the addition of either Silane A-137 and MAPE or Silane A-1100 and MAPE at different ratios into the wood-PVC/LDPE composites was also studied. The experimental results suggested that the optimum mechanical properties could be obtained using Silane A-137 : MAPE of 1% : 2% wt sawdust. The morphological and thermal properties of the composites were also examined using SEM and DMA techniques, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

硅烷偶联剂对玻纤/聚丙烯复合材料的影响

分别选用KH550、KH570两种硅烷偶联剂处理无碱无捻粗纱,采用挤出、注塑成型技术制备玻纤增强聚丙烯复合材料,对复合材料进行了分析和研究。结果表明：硅烷偶联剂具有提高GF/PP复合材料性能的作用。SEM显示KH570处理GF与PP基体之间形成了良好的界面,界面层起到很好的应力传递作用,达到良好的增强效果。     

偶联剂对聚乳酸/蔗渣纤维复合材料力学性能的影响

采用了4种硅烷偶联剂处理甘蔗渣,研究了偶联剂品种和含量对聚乳酸/甘蔗渣复合材料力学性能的影响,并运用扫描电子显微镜对复合材料的冲击断面进行了观察。结果表明,甘蔗渣经过硅烷偶联剂表面处理后,聚乳酸/甘蔗渣复合材料的力学性能较未处理体系有不同程度的提升,其中Z-6032的处理效果最佳。聚乳酸/甘蔗渣复合材料的力学强度受甘蔗渣粒径和含量的影响;甘蔗渣的粒径越小,复合材料的冲击强度越大;随着甘蔗渣含量的增大,复合材料的冲击强度和拉伸强度均呈下降趋势。     

Adhesion between ethylene-propylene-diene monomer and thermoplastics in two-component injection molding: Effect of dicumylperoxide as curing agent

Strong adhesion at the interface is an important aspect in two-component (2K) injection molding. It was therefore investigated whether dicumylperoxide (DCP) as curing agent in ethylene-propylene-diene monomer (EPDM) could stimulate interdiffusion and/or induce chemical bonding with thermoplastics. EPDM mixtures containing DCP concentrations between 2 to 8 parts per hundred rubber (phr) were combined with polar and non-polar thermoplastics. Changes in EPDM physico-mechanical bulk properties were analyzed, and the adhesion was evaluated by high temperature contact angle measurements and tensile testing. Results showed that DCP concentration did not influence EPDM-thermoplastic compatibility. However, EPDM adhesion with polyethylene (PE) did improve when using up to 6 phr DCP (57% adhesion) as crosslinking is promoted. While with polypropylene (PP), adhesion linearly decreased (from 55% to 35% adhesion) with higher DCP concentrations due to prevailing scission reactions. Adhesion through chemical bonding with acrylonitrile-butadiene-styrene (ABS) caused better adhesion at 4 phr (43% adhesion) compared to polycarbonate (PC) at 4 phr (13% adhesion) where only limited interdiffusion occurs. Thus, selecting the optimal DCP concentration is highly important to boost adhesion between EPDM and thermoplastics. Furthermore, at these optimal DCP concentrations, physico-mechanical properties require consideration as these properties were significantly affected.     

Laser‐induced plasma spectroscopy for plastic identification

The goal of this work was instant identification of post‐consumer plastics by laser induced plasma spectrometry (LIPS). LIP spectra from plastics in a 200–800 nm spectral window were compared with reference spectral libraries stored in a computer. The libraries consisted of representative spectra from different groups of recycled plastic samples. The plasma emission spectra of polyethylene terephthalate (PET), high density polyethylene (HDPE), polyvinyl chloride (PVC), low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were studied. Simple statistical correlation methods including linear and rank correlations were used. The probabilities of correct identification ranged from 0.8 to 1 with values close to unity for most of the polymers studied.     

Physical properties of straw lignin-based polymer blends

Lignin powder, obtained from an abundant and low cost source, straw, through a low environmental impact process, the steam explosion, is used for the preparation of blends with low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and atactic polystyrene (PS).The obtained blends are processable through the conventional techniques used for thermoplastics; the modulus slightly increases for most lignin-polymer blends, while the tensile stress and elongation reduce. Moreover, lignin acts as a stabilzer against the UV radiation for PS, LDPE and LLDPE.     

Crosslinkable polypropylene composites made by the introduction of silane moieties

Silane‐crosslinkable polypropylene (PP) composites containing calcium carbonate (CaCO₃) as a filler have been investigated. The melt grafting of vinyl trimethoxysilane to PP with dicumyl peroxide (DCP) as a radical initiator is demonstrated. The thermal and mechanical properties of the crosslinkable products are also discussed. The results show that two reactions, that is, silane grafting and PP degradation, take place in parallel. The extents of silane grafting and PP degradation strongly depend on the reaction temperature, grafting formulation, and amount of the filler in the systems. Increasing the DCP concentration (up to 0.05 wt %) leads to an increase in the grafting degree. However, when the concentration of radicals is over a certain degree, the dominant reaction is PP chain scission. This results in a drastic decrease in the polymer viscosity. In systems containing both silane and CaCO₃, the viscosity of the polymer is higher than that of a grafted sample without CaCO₃ addition; in other words, the effect of the filler on the polymer viscosity compensates for the effect caused by PP degradation. Differential scanning calorimetry results show that the crystallization starts earlier for grafted samples. The percentage of the crystallinity of grafted PP is higher than that of the pure polymer. The incorporated silane does not have a strong effect on the mobility of the PP chains, as revealed by dynamic mechanical analysis. In comparison with ungrafted composites, the silane‐crosslinkable products show higher tensile stress and modulus. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1476–1483, 2005