Effect of temperature on hygroscopic thickness swelling rate of composites from lignocellolusic fillers and HDPE

Effect of temperature on hygroscopic thickness swelling rate of lignocellolusic fillers/HDPE (high density polyethylene) composites was investigated. The composites were manufactured using a dry blend/hot press method. In this method, powder of plastic and dried powder of lignocellolusic material were mixed in high‐speed mixer and then the mixed powder were pressed at 190°C. Lignocellolusic fillers/HDPE composites panels were made from virgin and recycled HDPE (as plastic) and wood sawdust and flour of rice hull (as filler) at 60% by weight filler loadings. Nominal density and dimensions of the panels were 1 g/cm³ and 35 × 35 × 1 cm³, respectively. Thickness swelling rate of manufactured wood plastic composites (WPCs) were evaluated by immersing them in water at 20, 40, and 60°C for reaching a certain value where no more thickness was swelled. A swelling model developed by Shi and Gardner [Compos. A, 37 , 1276 (2006)] was used to study the thickness swelling process of WPCs, from which the parameter, swelling rate parameter, can be used to quantify the swelling rate. The results indicated that temperature has a significant effect on the swelling rate. The swelling rate increased as the temperature increased. The swelling model provided a good predictor of the hygroscopic swelling process of WPCs immersed in water at various temperatures. From the activation energy values calculated from the Arrhenius plots, the temperature had less effect on the thickness swelling rate for the composites including wood sawdust compared with the rice hull as filler and the composites including recycled compared with the virgin HDPE as plastic. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effects of the accelerated freeze‐thaw cycling on physical and mechanical properties of wood flour‐recycled thermoplastic composites

This study investigated durability performance of wood‐plastic composites (WPCs) that were exposed to accelerated cycling of water immersion followed by freeze thaw (FT). The WPCs used in this study were made of high‐density polyethylene (HDPE) or polypropylene (PP) with radiata pine (Pinus radiata) wood flour using hot‐press molding. These two types of plastics included both recycled and virgin forms in the formulation. In the experiments, surface color, flexural properties, and dimensional stability properties (water absorption and thickness swelling) were measured for the FT cycled composites and the control samples. Interface microstructures and thermal properties of the composites were also investigated. The results show that the water absorption and the thickness swelling of the composites increased with the FT weathering. In the meantime, the flexural strength and stiffness decreased. Scanning electron microscopy (SEM) images of the fractured surfaces confirmed a loss of interface bonding between the wood flour and the polymer matrix. Differential scanning calorimetry (DSC) showed a decrease in crystallization enthalpy and crystallinity of the wood flour‐plastic composites as compared with the neat PP and HDPE samples. The crystallinity of the FT cycled composites using the virgin plastics (vPP and vHDPE) increased; however, the composites with the recycled plastics decreased in comparison with corresponding control samples. In general, the properties of the composites were degraded significantly after the accelerated FT cycling. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

The physical perspective on the solid and molten states associated with the mechanical properties of eco‐friendly HDPE/Pinus taeda wood‐plastic composites

The manufacture of wood plastic composites (WPCs) by reutilizing post‐consumed polymeric materials and post‐industry wood wastes contributes to reduce the environmental impact and the consumption of virgin plastics. In this work, the influence of interfacial adhesion on the solid and molten states of high density polyethylene (HDPE) containing WPCs wood dust of recycled Pinus taeda (PT) was evaluated. The composites were prepared by extrusion in a twin screw extruder using maleic anhydride as compatibilizer. The samples were analyzed by dynamic‐mechanical analysis (DMA), tensile and impact strength measurements, oscillatory rheometry, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). DMA analysis showed increase in module and an improved interface with physical interaction between the WPCs phases. The higher molecular interactivity interface improved the mechanical properties relative to pure HDPE. Melting state analysis showed increased WPCs flow restriction, this feature being correlated with reduction in the molecular degree of freedom during flow, which consequently reduces the crystalline degree changes in microstructure as well as in processing parameters of the material. These results lead to consider the development of an eco‐friendly and economic effective technology to reuse abundant recycled solid wastes in a new market. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42887.     

Impact strength improvement of wood flour–recycled polypropylene composites

In this research, the improvement of the impact strength of wood flour–recycled polypropylene (PP) composites through impact modification was studied. For this purpose, a virgin polypropylene (VPP) was thermomechanically degraded by five extrusions under controlled conditions in a twin‐screw extruder at a rotor speed of 100 rpm and a temperature of 190°C. PP (VPP and recycled PP at the second and fifth stages) and wood flour were compounded at 50 wt % wood flour loading in a counterrotating twin‐screw extruder in the presence different contents of ethylene vinyl acetate (EVA) to produce the wood flour–PP composites. From the results, the composites containing recycled PP exhibited significantly lower impact strengths. The addition of EVA up to 9 wt % increased the impact strengths of the composites made with PP recycled two and five times by about 63 and 41%, respectively. The composites containing VPP exhibited higher impact strengths than those containing recycled PP and EVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of recycled polypropylene on polypropylene/high‐density polyethylene blends

The effect of recycled PP on incompatible blends of virgin polypropylene (PP) and high‐density polyethylene (HDPE) was studied. Recycled PP from urban solid waste was extracted with methyl ethyl ketone and the compatibilizing action of the product before and after extraction was examined. The characterization of the recycled PP was performed by FTIR, NMR, and DSC analyses. Mechanical properties of the blends were evaluated. The results showed partial compatibility of the blend components, reflected in the improvement of the tensile strength and elongation. Best results were achieved by the addition of extracted recycled PP on the 50/50 PP/HDPE blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1305–1311, 2001     

废旧汽车门内饰板聚丙烯塑料同等性能再利用

以乘用车废旧门内饰板聚丙烯塑料为研究对象,通过共混改性研究其性能变化规律、机理,实现回收料的同等性能再利用。采用聚丙烯新料(VPP)、乙烯–辛烯共聚物(POE)对回收PP(RPP)进行共混改性,研究VPP和POE的添加量对复合体系力学性能的影响规律及改善机理。结果表明,VPP的加入可以显著提高RPP/VPP复合体系的拉伸性能、弯曲性能和流动性能;POE含量越高,RPP/VPP/POE复合体系的冲击强度越大;当RPP/VPP/POE=54/36/10时,复合体系的综合性能满足汽车门内饰板的性能要求,实现废旧材料的同等性能再利用。     

Recycling of commingled plastics waste containing polypropylene,polyethylene, and paper

Polymer waste recycling is a major technical problem, because large amounts of synthetic polymers are produced every day and polymeric wastes are gathered from municipal solid wastes. There are a few polyolefins, such as polyethylene (PE) and polypropylene (PP) with huge amounts of paper in the waste materials. In order to recycle the commingled plastics waste that contains paper, hydrolytic treatment is needed prior to conventional processing. In this project, the optimum conditions of hydrolytic treatment of paper and the mechanical properties and morphological state of different compositions of PP high‐density PE (HDPE) blends with paper were studied. Ethylene‐propylene‐diene copolymer (EPDM) was added to improve the mechanical properties of blends. The results show that the hydrolytic treatment of paper improves the mechanical properties, such as the tensile strength and modulus of the PP/HDPE/paper composites relative to the untreated samples, and up to 30% paper can be added to commingled PP and HDPE blends. The EPDM was used as an impact modifier. The plastics waste containing paper can be used in applications such as artificial wood. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2573–2577, 2001     

Recycled car bumpers' impact resistance investigated by wide‐angle X‐ray diffraction

The recycled polyolefinic product from discarded standard car bumpers collected from Rio de Janeiro suburb shops was characterized by mechanical and wide‐angle X‐ray scattering (WAXS) methods. We found that the recycled plastic mixture is composed mainly of polypropylene (PP), containing ethylene‐propylene‐diene (EPDM) terpolymers and a minor proportion of high‐density polyethylene (HDPE), and is highly resistant to impact. The results were compared with the corresponding data obtained from binary and ternary blends of virgin PP, EPDM, and HDPE. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 999–1004, 2000     

加工助剂TKM80在木塑复合材料中的应用研究

研究了加工助剂60NSF,TKM80,WB16对聚丙烯(PP)基木塑复合材料机械性能和流变性能的影响。结果表明,60NSF,TKM80,WB16这3种助剂中TKM80对木塑复合材料机械性能的提高最大,与未加TKM80比较,当TKM80用量为7.5份时,木塑复合材料的拉伸强度提高20.9%,冲击强度提高55.6%,加工流变性得到很大的提高;从试样的冲击断裂面的扫描电镜照片,可以看出TKM80能够提高木粉在PP基体中的分散性,并改善PP与木粉之间的相容性。     

Compatibility of HDPE/postconsumer HDPE blends using compatibilizing agents

Mechanical properties, molecular weight, X‐ray diffraction, and differential scanning calorimetry (DSC) characterization of blends of virgin high‐density polyethylene (HDPE) with two types of recycled material were investigated. The recycled came from urban plastic waste; one kind was only washed and grounded and the other was extruded and pelletized to remove most of contaminant particles. Starting with the 30/70 virgin/grounded recycled and 50/50 virgin/pelletized recycled blends the recycled content was increased in both blends and compatibilizing agents were used to increase the blend performance. A mixture of phenolic antioxidants and phosphite costabilizers under the name of Recycloblend?, ethylene vinyl acetate (EVA) copolymer, low‐density polyethylene (LDPE), and linear low density polyethylene (LLDPE) were used as compatibilizers. The effect of these additives and the recycled content on the performance of extrusion blow‐molded bottles was determined. The results suggest that blends of virgin/grounded recycled and virgin/pelletized recycled HDPE, in general, were not significantly different among each other and both had a quite similar behavior than the virgin HDPE when compatibilizing agents were used. The addition of compatibilizing agents yielded a material with properties similar to those for the virgin HDPE, helping to reduce the effect of polymers degradation on the rheological and mechanical behavior, with Recycloblend and LLDPE being the most effective for the blends with grounded recycled material, and LLDPE y EVA, for the blends with pelletized recycled. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3696–3706, 2006     

Rheological and mechanical properties of composites made from wood flour and recycled LDPE/HDPE blend

The effect of compounding method is studied with respect to the rheological behavior and mechanical properties of composites made of wood flour and a blend of two main components of plastics waste in municipal solid waste, low-density polyethylene (LDPE) and high-density polyethylene (HDPE). The effects of recycling process on the rheological behavior of LDPE and HDPE blends were investigated. Initially, samples of virgin LDPE and HDPE were thermo-mechanically degraded twice under controlled conditions in an extruder. The recycled materials and wood flour were then compounded by two different mixing methods: simultaneous mixing of all components and pre-mixing, including the blending of polymers in molten state, grinding and subsequent compounding with wood flour. The rheological and mechanical properties of the LDPE/HDPE blend and resultant composites were determined. The results showed that recycling increased the complex viscosity of the LDPE/HDPE blend and it exhibited miscible behavior in a molten state. Rheological testing indicated that the complex viscosity and storage modulus of the composites made by pre-mixing method were higher than that made by the simultaneous method. The results also showed that melt pre-mixing of the polymeric matrix (recycled LDPE and HDPE) improved the mechanical properties of the wood–plastic composites.     

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     

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.     

Recycling of commingled plastics by cellulosic reinforcement

In this article, a model study was conducted on the effect of combining cellulose on the properties of virgin and/or recycled commingled plastics with a simulated waste‐plastics fraction composed of high‐density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(vinyl chloride) (PVC) (PE/PP/PS/PVC = 7/1/1/1 by weight ratio). The compatibilizing effect of maleic anhydride‐grafted styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MAH) for the cellulose‐reinforced commingled blends was also investigated. Commingled blends were prepared in a table kneader internal mixer. Mechanical properties were measured by using a universal testing machine. Thermal stability was measured by a thermogravimetric analyzer. It was found that the addition of more than 12.5% cellulose into the commingled blends was effective to enhance the mechanical properties of the virgin and recycled blends. The thermal stability as well as the mechanical properties of the commingled blends were much improved by the reactive blending of cellulose with the commingled blends by peroxide and maleic anhydride. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1531–1538, 1999     

Relationship between cell morphology and impact strength of microcellular foamed high‐density polyethylene/polypropylene blends

Polymer blends, such as those resulting from recycling postconsumer plastics, often have poor mechanical properties. Microcellular foams have been shown to have the potential to improve properties, and permit higher‐value uses of mixed polymer streams. In this study, the effects of microcellular batch processing conditions (foaming time and temperature) and HDPE/PP blend compositions on the cell morphology (the average cell size and cell‐population density) and impact strength were studied. Optical microscopy was used to investigate the miscibility and crystalline morphology of the HDPE/PP blends. Pure HDPE and PP did not foam well at any processing conditions. Blending facilitated the formation of microcellular structures in polyolefins because of the poorly bonded interfaces of immiscible HDPE/PP blends, which favored cell nucleation. The experimental results indicated that well‐developed microcellular structures are produced in HDPE/PP blends at ratios of 50:50 and 30:70. The cell morphology had a strong relationship with the impact strength of foamed samples. Improvement in impact strength was associated with well‐developed microcellular morphology. Polym. Eng. Sci. 44:1551–1560, 2004. © 2004 Society of Plastics Engineers.     

Mechanical and thermal properties of wood‐plastic composites reinforced with hexagonal boron nitride

Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers     

几种木塑复合材料的性能对比

研究了木粉及界面增容剂含量对木塑复合材料(WPC)力学性能的影响,分析了增容剂对WPC熔融性能的变化。使用木粉填充可提高不同树脂基WPC的模量,但却降低了HDPE基WPC的拉伸强度及HDPE基、PP基WPC的弯曲强度。     

Experimental investigation on reprocessing of extruded wood flour/HDPE composites

This article presents an experimental study on the change in the properties of wood–plastic composites (WPCs) when reprocessed. The degree of properties degradation upon reprocessing, for recycling purpose, can be considered as a key factor to choose an alternative against discarding into the environment. A material which retains its properties when recycled, or at least exhibits insignificant reduction in its properties, is favorable in environmental point of view. To investigate the reprocessing effect on the WPC properties, in this study, cylindrical profiles of WPC, with 60 wt% of wood content, were produced using a twin screw extruder, at first stage (virgin WPC). These profiles were then chopped into granules and used in the reproduction of the same shaped product (recycled WPC). For the measurement of mechanical properties, tensile and three‐point bending tests were conducted. Differential scanning calorimetry (DSC) test was performed to compare thermal behavior of the neat HDPE, virgin and recycled composites. Scanning electron microscopy (SEM) images were also produced to observe the adhesion quality of the components and changes in wood particles size. Physical properties such as density and water uptake were also measured. A reduction in strength was observed upon recycling which was accompanied with the decrease in density, while an increase in the flexural modulus was noticed. The results also indicate that the recycled samples exhibit a higher water uptake. Analysis of thermal behavior showed a slight increase in the melting temperature of the reprocessed composite and decrease in the degree of crystallinity especially at the first stage of the HDPE process. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of highly degraded high‐density polyethylene (HDPE) on processing and mechanical properties of wood flour‐HDPE composites

The influence of highly degraded high‐density polyethylene (HDPE) on physical, rheological, and mechanical properties of HDPE‐wood flour composites was studied. For this purpose, the virgin HDPE was subjected to accelerated weathering under controlled conditions for 200 and 400 h. The virgin and exposed HDPE and pine wood flour were compounded to produce wood flour‐HFPE composites. The results showed that the accelerated weathering highly degraded HDPE. Degradation created polar functional carbonyl groups and also produced extensive cross‐linking in HDPE and consequently poor processibility. The interruptions in the flow characteristics of the degraded HDPE potentially caused processing hurdles when using them for extrusion or injection molding manufacturing as only small part (10%) of virgin HDPE could be replaced by highly degraded HDPE for wood flour‐HDPE composite manufacturing. The mechanical properties of composites containing highly degraded HDPEs were similar to the composites with virgin HDPE and in some cases they exhibited superior properties, with the exception being with the impact strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

纳米CaCO3和玻纤增强PVC、HDPE、PP的力学性能研究

对聚氯乙烯(PVC)、高密度聚乙烯(HDPE)、聚丙烯(PP)三种通用树脂进行玻璃纤维增强、无机纳米粒子改性制备热塑性树脂基纳米复合材料,可在复合材料与树脂成本基本持平的条件下,使复合材料的力学性能比基体树脂有较大提高,接近甚至达到了工程塑料的水平,为通用塑料工程化探索一行之有效的技术途径。