Mechanical properties of recycled LDPE/EVA/ground tyre rubber blends: Effects of EVA content and postirradiation

Thermoplastic elastomers were prepared from recycled low density polyethylene [rLDPE] and virgin low density polyethylene (LDPE), respectively, ground tyre rubber (GTR), and ethylene vinyl acetate (EVA) copolymer. The amounts of the rLDPE and GTR were fixed at 40 and 30 wt %, respectively, in the formulations, whereas the LDPE and EVA contents varied each between 0 and 30 wt %. The fresh LDPE served for reduction of the melt viscosity and EVA was used for improving the elastomeric properties. Blends of different compositions (by varying the LDPE/EVA ratio) were produced by twin-screw extrusion and pelletized. Specimens were produced by injection molding and subjected to tensile and instrumented falling weight impact (IFWI) tests. To improve the mechanical performance of the blends, the injection molded specimens were electron beam irradiated at 150 kGy absorbed dose. Static tensile and hysteresis, IFWI and dynamic mechanical thermal analysis tests were performed on the specimens and the fracture surface was inspected with a scanning electron microscope. The results indicated that better rubber-like properties were achieved with increasing EVA content. Moreover, postirradiation proved to be very beneficial, especially for blends containing relative high amounts of EVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Recycled milk pouch and virgin LDPE‐LLDPE‐based jute fiber composites

The present investigation deals with the thermo‐mechanical recycling of post consumer milk pouches (LDPE‐LLDPE blend) and its use as jute fiber composite materials for engineering applications. The mechanical, thermal, morphological, and dynamic‐mechanical properties of recycled milk pouch‐based jute fiber composites with different fiber contents were evaluated and compared with those of the virgin LDPE‐LLDPE/jute fiber composites. Effect of artificial weathering on mechanical properties of different formulated composites was determined. The recycled polymer‐based jute fiber composites showed inferior mechanical properties as well as poor thermal stability compared to those observed for virgin polymer/jute fiber composites. However, the jute‐composites made with (50:50) recycled milk pouch‐virgin LDPE‐LLDPE blend as polymer matrix indicated significantly superior properties in comparison to the recycled milk pouch/jute composites. Overall mechanical performances of the recycled and virgin polymeric composites were correlated by scanning electron microscopy (SEM). The dynamic mechanical analysis showed that storage modulus values were lower for recycled LDPE‐LLDPE/jute composites compared to virgin LDPE‐LLDPE/jute composites throughout the entire temperature range, but an increase in the storage modulus was observed for recycled‐virgin LDPE‐LLDPE/jute composites. POLYM. COMPOS. 28:78–88, 2007. © 2007 Society of Plastics Engineers     

Recycled milk pouch and virgin low‐density polyethylene/linear low‐density polyethylene based coir fiber composites

The viability of the thermomechanical recycling of postconsumer milk pouches [a 50 : 50 low‐density polyethylene/linear low‐density polyethylene (LDPE–LLDPE) blend] and their use as polymeric matrices for coir‐fiber‐reinforced composites were investigated. The mechanical, thermal, morphological, and water absorption properties of recycled milk pouch polymer/coir fiber composites with different treated and untreated fiber contents were evaluated and compared with those of virgin LDPE–LLDPE/coir fiber composites. The water absorption of the composites measured at three different temperatures (25, 45, and 75°C) was found to follow Fickian diffusion. The mechanical properties of the composites significantly deteriorated after water absorption. The recycled polymer/coir fiber composites showed inferior mechanical performances and thermooxidative stability (oxidation induction time and oxidation temperature) in comparison with those observed for virgin polymer/fiber composites. However, a small quantity of a coupling agent (2 wt %) significantly improved all the mechanical, thermal, and moisture‐resistance properties of both types of composites. The overall mechanical performances of the composites containing recycled and virgin polymer matrices were correlated by the phase morphology, as observed with scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

An investigation for the effect of recycled matrix on the properties of textile waste cotton fiber reinforced (T‐FRP) composites

The main objective of this research is to study the effect of recycled low density polyethylene (r‐LDPE) matrix on the tensile, impact, and flexural properties of the novel textile waste cotton fiber reinforced (T‐FRP) composites. For this purpose, the T‐FRP composites were manufactured by using two different matrix types; namely, virgin LPDE (v‐LDPE) and r‐LDPE, with different waste cotton fiber content. All composites were compatibilized by maleic anhydride‐LDPE (MA‐LDPE) in order to increase the interfacial adhesion between fibers and matrices. Differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic mechanical analyzer studies were performed in order to characterize the materials. The results have shown that best tensile and flexural properties have been obtained from the composites with the content of 30 wt% cotton fiber, 5 wt% maleic anhydride‐LDPE, and 65 wt% recycled LDPE matrix. However, the impact properties of the composites were decreased drastically compared to the pure LDPE matrix. POLYM. COMPOS., 38:1231–1240, 2017. © 2015 Society of Plastics Engineers     

Mechanical, electrical, and thermal properties of irradiated low-density polyethylene by electron beam

The effect of electron-beam (EB) irradiation on the mechanical, electrical, and thermal properties of low-density polyethylene (LDPE) was studied The LDPE was irradiated by using 3?MeV EB machine at doses ranging from 25 to 250?kGy in air at room temperature and analyzed for mechanical, thermal, and electrical properties. It was revealed by differential scanning calorimetry analysis that the crystallinity of the EB-radiated LDPE decreased slightly as verified by a marginal reduction in the densities, enthalpy, and melting points. Thermogravimetric analysis test showed that the thermal degradation of LDPE improved by increasing irradiation. The results obtained from both gel content and hot set tests, indicating whether the applicable LDPE has been properly cross-linked or not, showed that under the EB irradiation conditions employed, the cross-linking of the LDPE samples occur mainly in the amorphous region, and the cross-linking density at each irradiation dose depends almost on the amorphous portions of the LDPE. A significant improvement in the tensile strength of the neat LDPE samples was obtained upon EB up to 250?kGy with a concomitant decline in elongation at break. The results on the electrical properties revealed that the surface resistance, volume resistivity, and dielectric strength of the LDPE increase with irradiation dose and reaches a maximum at a 250?kGy irradiation dose. No considerable change of breakdown voltage, dielectric constant, and dielectric loss factor were observed with increasing irradiation dose. The enhancement in the heat deformation, hardness, and thermal aging properties of LDPE upon EB irradiation, suggests that irradiated LDPE is more thermally and mechanically stable than virgin LDPE.     

Degradation behavior of poly (caprolactone)–poly(ethylene glycol) block copolymer/low–density polyethylene blends

Blends of poly(carprolactone)-poly(ethylene glycol) block polymer (PCE) with low-density polyethylene (LDPE) were prepared by extrusion followed by compression molding into thin film specimens. The morphology, thermal properties, degradation, and mechanical behavior of the blends were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), water immersion, static tensile testing, and dynamic mechanical analysis (DMA). The LDPE/PCE blends were immiscible for all chemical compositions. A LDPE/PCE (75/25 wt%) blend exhibited small reductions in weight and tensile strength after immersion in a buffer solution (pH = 5.0) at 50°C for extended periods of time. However, grafting maleic anhydride onto the LDPE/PCE blends improved the compatibility between the LDPE and PCE phases. Consequently, a 75/25 wt% blend of maleated LDPE/PCE exhibited significant losses in weight and tensile strength after immersion in the buffer solution. For comparison, blends of poly(caprolactone) (PCL) with LDPE were fabricated by similar techniques. The effect of compatibilizer on the degradation of LDPE/PCE and LDPE/PCL is discussed.     

农用薄型茂金属聚乙烯棚膜的开发与应用

以mLLDPE／LDPE共混树脂为主要原料，采用有膜泡内冷装置的3层共挤复合宽幅吹膜机组和6911／B215耐老化体系生产的薄型茂金属聚乙烯棚膜具有优异的综合力学性能和耐老化性能，应用效果良好。     

Recycling of poly(ethylene terephthalate) as polymer‐polymer composites

Microfibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide‐angle X‐ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer‐polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations. The MFC dogbone samples show impressive mechanical properties—the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short‐glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers.     

Mechanical,morphological, and thermal properties of poly(vinyl chloride)/low‐density polyethylene composites filled with date palm leaf fiber

This article investigates the mechanical, morphological, and thermal properties of poly(vinyl chloride) (PVC) and low‐density polyethylene (LDPE) blends, at three different concentrations: 20, 50, and 80 wt% of LDPE. Besides, composite samples that were prepared from PVC/LDPE blend reinforced with different date palm leaf fiber (DPLF) content, 10, 20, and 30 wt%, were also studied. The sample in which PVC/LDPE (20 wt%/80 wt%) had the greatest tensile strength, elongation at break, and modulus. The good thermal stability of this sample can be seen that T_10% and T_20% occurred at higher temperatures compared to others blends. DPLF slightly improved the tensile strength of the polymer blend matrix at 10 wt% (C10). The modulus of the composites increased significantly with increasing filler content. Ageing conditions at 80°C for 168 h slightly improved the mechanical properties of composites. Scanning electron microscopic micrographs showed that morphological properties of tensile fracture surface are in accordance with the tensile properties of these blends and composites. Thermogravimetric analysis and derivative thermogravimetry show that the thermal degradation of PVC/LDPE (20 wt%/80 wt%) blend and PVC/LDPE/DPLF (10 and 30 wt%) composites took place in two steps: in the first step, the blend was more stable than the composites. In the second step, the composites showed a slightly better stability than the PVC/LDPE (20 wt%/80 wt%) blend. Based on the above investigation, these new green composites (PVC/LDPE/DPLF) can be used in several applications. J. VINYL ADDIT. TECHNOL., 25:E88–E93, 2019. © 2018 Society of Plastics Engineers     

Effects of dynamic elongational flow on the dispersion and mechanical properties of low‐density polyethylene/nanoprecipitated calcium carbonate composites

Low‐density polyethylene (LDPE)/nanoprecipitated calcium carbonate (NPCC) nanocomposites were prepared with a self‐made vane extruder (VE) that generates global dynamic elongational flow and with a single‐screw extruder (SSE) that generates low shear flow. The mechanical properties, dispersed phase morphology, and thermal behavior of the nanocomposites were investigated to compare the different processing techniques. Scanning electron micrograph and transmission electron micrograph show that the elongational flow in the VE improves the dispersion of NPCC (5 wt%) particles in the LDPE matrix. The dimensional distribution of NPCC particles in the VE is significantly lower than that of the SSE. Differential scanning calorimetric curves indicate that dynamic elongational flow can enhance the crystallization ability of the LDPE/NPCC nanocomposites. The mechanical properties of the VE‐extruded samples are superior to those of the SSE‐extruded samples. When compared with that of SSE, morphology of tensile fracture surfaces suggests that the uniform and fine dispersion of NPCC particles in the LDPE matrix can successfully improve modulus and toughness of the LDPE/NPCC nanocomposites based on the novel VE. POLYM. COMPOS., 35:884–891, 2014. © 2013 Society of Plastics Engineers     

木质素填充LDPE、EVA对复合物性能的影响

以木质素为填充剂分别与低密度聚乙烯(LDPE)、乙烯-乙酸乙烯酯共聚物(EVA)共混,经双螺杆造粒机共混挤出造粒,再经吹塑成膜。研究了木质素/LDPE、木质素/EVA共混物薄膜的表面形貌、力学性能、热性能和红外光谱。热分析表明木质素与EVA共混物的热稳定性比木质素与LDPE的共混物热稳定性好;红外光谱分析表明木质素与EVA分子间产生了强烈的相互作用,扫描电镜分析表明木质素与EVA共混的相容性较好,力学性能分析表明低于30%的木质素与LDPE、EVA共混力学性能较好。     

Mechanical properties of foams comprising virgin and waste polyethylene

Summary This paper addresses the use of waste polyethylene (p-PE) in low-density polyethylene (LDPE) foams with azodicarbonamide as the blowing agent. The amount of blowing agent was fixed at 5% for all mixtures, with 0.5% cross-linking agent, 1.7% zinc oxide and 1.7% stearic acid, by weight. Proportions of LDPE/p-PE (% wt) tested in foams were: 100/0, 85/15, 70/30, 60/40, 50/50 and 30/70. The components used to obtain the foams were processed in a Banbury mixer at 120 °C. The pre-form (non expanded material) was placed in a mold and the foaming was carried out in a hot press at 190 °C. The apparent densities of the foams obtained were 60–65 kg.m^-3. The mechanical properties (compression set under constant deflection, compressive strength and tear resistance) of LDPE foams containing different proportions of p-PE were compared with the LDPE foam obtained from virgin material only. The mechanical properties of foams with p-PE in their formulation were superior in relation to foams made from LDPE, because p-PE contains high-density polyethylene (HDPE), which is more rigid than LDPE.     

Properties of silanized nypa fruticans filled polylactic acid/recycled low density polyethylene biocomposites

The biocomposites of Nypa Fruticans (NF) and Polylactic acid (PLA)/recycled low density polyethylene (rLDPE) were prepared using Brabender EC PLUS. The effect of NF content and silane coupling agent on mechanical, thermal, and morphological properties were studied. The results show that addition of NF in PLA/rLDPE biocomposites have decreased the tensile strength, elongation at break, and crystallinity of biocomposites. The Young's modulus of biocomposites and thermal stability increased with the increasing NF content. The surface of NF fillers were silanized to improved the interfacial adhesion between the NF filler and PLA/rLDPE matrix. It was found that the tensile strength, Young's modulus, crystallinity of PLA, and thermal stability of silanized biocomposites higher as compared to untreated biocomposites. The enhancement of the properties of biocomposites with silane treatment was proven by SEM studied. The silanized biocomposites showed better interfacial interaction and adhesion between NF and PLA/rLDPE matrix. POLYM. ENG. SCI., 55:1733–1740, 2015. © 2014 Society of Plastics Engineers     

分子量分布对低密度聚乙烯光氧老化特性的影响

采用衰减全反射红外光谱技术（ATR-FTIR）、热重分析法（TG）、凝胶渗透色谱（GPC）、扫描电子显微镜（SEM）和力学试验比较研究了不同分子量分布指数低密度聚乙烯（LDPE）的光氧老化特性,分析了分子量分布对LDPE化学结构、热稳定性、平均分子量、表面微观形貌和力学性能的影响规律。结果表明分子量分布越宽,LDPE不饱和度增长越剧烈,支化作用增长越显著;分子量分布越窄,羰基指数增长越快;分子量分布对于分子结构的断链行为并无影响。分子量分布指数越大,LDPE起始热分解温度和失重5%对应温度下降更快,热稳定性更容易变差,平均分子量下降更多,表面微观形貌老化现象越严重;弯曲强度和冲击强度受影响更显著,指数为6.0的LDPE老化24 d冲击强度就已丧失。分析认为,分子量越大、分布越窄表明分子链越长、短分子链越少,与氧接触而产生自由基的概率也越小,因此聚乙烯分子量分布越宽,材料越容易老化。     

Natural and artificial weathering of low-density polyethylene (LDPE): Calorimetric analysis

Studies of the thermal and photodegradation of two commercial polymers, stabilized and unstabilized low-density polyethylene (LDPE), show the effects of weathering in differential scanning calorimetry (DSC) curves. The shape and the size of the melting peak vary significantly in thermal aging and in accelerated photoirradiation, but no change was observed in natural weathering implying that the crystallinity remains steady in outdoor exposures. The melting temperatures remain steady for all exposure tests. The fall of mechanical properties and the evolution of chemical structure, followed by IR spectroscopy especially near the carbonyl regions, was also performed. The resistance to UV light irradiation as probed by deformation at break was superior in stabilized LDPE compared to unstabilized LDPE. Simple correlations were not observed between the fall of mechanical properties, the rate of oxidation, and the morphology.     

Approach in Macadamia integrifolia residue based low-density polyethylene composites on mechanical and thermal performance

Macadamia nutshell residues are generated in large quantities, around 70%–77% for each ton produced, and it is a waste material with high techno-economic potential. This work purpose a sustainable alternative to valorize macadamia nutshell residues (MN) as reinforcing in low-density polyethylene (LDPE) composites through melt mixing, using different fiber contents (0, 5, 10, and 20 wt%), and investigate the influence of fibers (residues) in composites by mechanical tests and thermal analysis. The fibers addition has significantly increased the composites' stiffness compared with neat LDPE, causing a reduction of toughness and resilience, leading to lower impact energy absorption. The LPDE/MN20% composite obtained the best tensile and flexural mechanical performance, resulting in a maximum modulus, which implies an increase of 36.9% and 77.6% compared with the neat LDPE. The addition of macadamia fibers on the composites acted as nucleation points of spherulites, which promoted an increase in the crystallization degree. Consequently, better performance of mechanical properties was observed in the green composites. Thus, the macadamia nutshell residues present a promising future as filler in LDPE for enhancing composites' thermal and mechanical properties.     

The Effect of NCO-Polyol on the Properties of Low-Density Polyethylene/Water Hyacinth Fiber (Eichhornia crassiper) Composites

Low density polyethylene (LDPE)/modified water hyacinth fiber (WHF) composites have been prepared by melt blending. All the composites were characterized by tensile test, differential scanning calorimetry (DSC), water absorption behaviour, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicated that LDPE/WHF composites with NCO-polyol as a coupling agent show higher values of tensile strength, Young's modulus and water absorption resistance but lower elongation at break than LDPE/WHF composites without NCO-polyol. The micrographs of SEM showed that the WHF were more widely dispersed in the LDPE matrix with the addition of the NCO-polyol as a coupling agent. It was also found that the modified WHF offers better thermal stability in the LDPE/WHF composites than unmodified WHF.     

Compatibilization of regenerated low density polyethylene/poly(vinyl chloride) blends

The aim of this work is to study the valorization of regenerated low density polyethylene (rLDPE) by blending with PVC in the presence of chlorinated polyethylene (CPE) as compatibilizer. For this purpose, four rLDPE samples coming from neat or dirty wastes were used. They were obtained after milling, washing, and extrusion in a conventional recycling plant. They were first characterized in terms of physicochemical (density, melt flow index, water absorption, and level of oxidation by Fourier transform infrared spectroscopy) and mechanical (tensile and shore D hardness) properties. The effect of the ratio of PVC on these physical and mechanical properties was then investigated. These binary blends exhibited lower properties than those of the separated polymers. The addition of CPE to the binary blend with weight proportion of 50/50 leads to a substantial improvement of the considered properties which is due to a better interfacial adhesion between rLDPE and PVC as evidenced by the analysis of the morphology of the blends by scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

利用回收LDPE/PVDC复合薄膜制备共混材料的研究

以回收低密度聚乙烯/聚偏氯乙烯(LDPE/PVDC)复合薄膜为基体材料,低密度聚乙烯接枝丙烯酸(LDPE-g-AA)为相容剂,线型低密度聚乙烯(LLDPE)为改性剂,再加入液体钙-锌(Ca-Zn)热稳定剂,通过混合、挤出、注塑工艺制备共混材料。采用刚果红法分析了Ca-Zn稳定剂对复合薄膜中PVDC热稳定性能的影响,并对共混材料的力学性能、阻隔性能和微观形态进行了测试与分析。结果表明:加入1.2份Ca-Zn稳定剂后,共混材料的刚果红试纸起始变色时间和完全变色时间分别延长了67 s和354 s,起始变色温度和完全变色温度分别提高了8℃和11℃;含3%LDPE-g-AA的共混材料,PVDC嵌入LDPE材料中,相容性明显改善,其缺口冲击强度和断裂伸长率提高,吸油率下降;含20%LLDPE及3%LDPE-g-AA的共混材料,其拉伸强度为14.43 MPa、断裂伸长率为389.11%、缺口冲击强度为29.51 kJ/m2、吸油率为14.40%,力学性能和阻隔性能优良。     

紫外线吸收剂在PLA/PBAT生物降解薄膜中的应用

通过挤出共混造粒、吹塑成型工艺制备出了聚乳酸(PLA)/聚对苯二甲酸-己二酸丁二醇酯(PBAT)完全生物降解薄膜。研究了一种二苯甲酮类紫外线吸收剂对PLA/PBAT薄膜抗紫外老化的作用。采用万能拉力试验机、紫外-可见吸光光谱仪、差示扫描量热法(DSC)对PLA/PBAT薄膜在紫外老化过程中的性能进行了测试和表征。结果表明,选择的紫外线吸收剂能有效减缓PLA/PBAT薄膜在老化过程中力学性能的下降。紫外老化更易发生在薄膜的无定型区,该紫外线吸收剂能明显降低薄膜在老化过程中结晶度的变化。同时,添加该紫外线吸收剂能大幅度降低薄膜在紫外老化过程中产生的凝胶含量。