Dynamic mechanical properties of high density polyethylene and teak wood flour composites

The dynamic mechanical properties of high density polyethylene (HDPE) and teak wood flour (TWF) composites at varying volume fraction (Φ _f) of TWF from 0.00 to 0.32 have been studied. In HDPE/TWF composites, storage modulus (E′) decreased at Φ _f = 0.05, then increases with Φ _f; however, values were lower than HDPE up to Φ _f = 0.16, due to a pseudolubricating effect of filler. Loss modulus (E″) values were higher than HDPE in β and α relaxation regions while in γ relaxation region values were marginally equal to HDPE. Tan δ value decreases with Φ _f which may be due to enhanced amorphization and decreased crystallinity of HDPE. In presence of maleic anhydride grafted HDPE (HDPE-g-MAH), E′ values were lower than HDPE/TWF composites. In HDPE/TWF/HDPE-g-MAH, E″ were slightly higher than HDPE/TWF due to slippage of HDPE chains facilitated by the extent of degradation of coupling agent. Tan δ were higher for both systems than the rule of mixture.     

Processability,morphology and mechanical properties of wood flour reinforced high density polyethylene composites

Abstract

Wood flour reinforced high density polyethylene (HDPE) composites have been prepared and their rheological properties measured. The melt viscosity decreased as the processing temperature increased and the wood flour content decreased. A power law model was used to describe the pseudoplasticity of these melts. Adding wood flour to HDPE produced an increase in tensile strength and modulus. Composites compounded in a twin screw extruder and treated with a coupling agent (vinyltrimethoxysilane) or a compatibliser (HDPE grafted with maleic anhydride) exhibited better mechanical properties than the corresponding unmodified composites because of improved dispersion and good adhesion between the wood fibre and the polyalkene matrix. Scanning electron microscopy of the fracture surfaces of these composites showed that both the coupling agent and compatibiliser gave superior interfacial strength between the wood fibre and the polyalkene matrix.     

Rheological behavior and mechanical properties of high‐density polyethylene blends with different molecular weights

The dynamic rheological and mechanical properties of the binary blends of two conventional high‐density polyethylenes [HDPEs; low molecular weight (LMW) and high molecular weight (HMW)] with distinct different weight‐average molecular weights were studied. The rheological results show that the rheological behavior of the blends departed from classical linear viscoelastic theory because of the polydispersity of the HDPEs that we used. Plots of the logarithm of the zero shear viscosity fitted by the Cross model versus the blend composition, Cole–Cole plots, Han curves, and master curves of the storage and loss moduli indicated the LMW/HMW blends of different compositions were miscible in the melt state. The tensile yield strength of the blends generally followed the linear additivity rule, whereas the elongation at break and impact strength were lower than those predicted by linear additivity; this suggested the incompatibility of the blends in solid state. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

HDPE/竹粉复合材料的界面演变及流变特性

采用扫描电子显微镜-X射线能谱仪跟踪硅烷偶联剂中Si元素在高密度聚乙烯(HDPE)基竹塑共混体系界面处的分布,并结合旋转流变仪研究了共混体系加工过程中的界面演变过程。发现随着加工时间的延长,界面处Si元素的含量相对增加,体系的动态模量、黏度升高。表明偶联剂连接的竹粉与HDPE分子链间的相互作用增强,界面层厚度增加。共混体系的动态流变测试结果表明,竹粉填充体系在低频末端区的线性黏弹行为显著不同于HDPE基体,表现出"类固体"特性,动态流变测试对偶联剂的加入所引起的体系的黏弹行为及结构变化响应较敏感。Cole-Cole曲线可反映竹粉粒子网络结构及竹粉与HDPE基体界面相关的松弛信息,体现体系界面性质及竹粉与分子链间网络结构的变化。     

Rheological and mechanical properties in polyethylene blends

Melt rheology and mechanical properties in linear low density polyethylene (LLDPE)/low density polyethylene (LDPE), LLDPE/high density polyethylene (HDPE), and HDPE/LDPE blends were investigated. All three blends were miscible in the melt, but the LLDPE/LDPE and HDPE/LDPE blends exibiled two crystallization and melting temperatures, indicating that those blends phase separated upon cooling from the melt. The melt strength of the blends increased with increasing molecular weight of the LDPE that was used. The mechanical properties of the LLDPE/LDPE blend were higher than claculated from a simple rule of mixtures, whiele those of the LLDPE/HDPE blend conformed to the rule of mixtures, but the properties of HDPE/LDPE were less than the rule of mixtures prediction.     

Rheological and mechanical properties of poly (ethylene acrylic acid) and low density polyethylene blends

Rheological properties of poly (ethylene‐acrylic acid) (PEA) and low density poly ethylene (LDPE) blends having varied amounts of LDPE from 0 to 100% have been evaluated at different temperatures (115, 120, and 130°C) and shear rates (61.33–613.30 s^?1) using a Monsanto processability tester. A reduction in the melt viscosity of the PEA/LDPE blends was noticed with increasing the shear rate. The observed positive deviation in the experimental melt viscosities of the blends is an indication of the synergy present in the blends during melt processing. The activation energy (E_a) of flow calculated using Arrhenius relation for PEA, LDPE, and their respective blends lies in the range 29.98–40.56 kJ mol^?1. The experimental activation energy of flow of the blends was higher than that obtained from the additivity rule. Highest activation energy was noticed for the blends containing 60–80% by weight of LDPE in PEA/LDPE blends, which is an indication for the miscibility of the blends at these ratios. The physicomechanical properties such as density, tensile behavior, tear strength, and hardness (Shore A) of PEA, LDPE, and their blends have been evaluated as a function of varying amounts of LDPE. The obtained physicomechanical properties of the PEA/LDPE blends lie in between that of pure polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Glass fiber/wood flour modified high density polyethylene composites

Composites of high density polyethylene (HDPE) with the reinforcements of glass fiber (GF) and wood flour (WF) have been studied in this work. High‐density polyethylene‐grafted maleic hydride (HDPE‐g‐MAH) was used as a compatibilizer. In particular, the effect of GF, WF, and HDPE‐g‐MAH on the overall properties of GF/WF/HDPE composites (GWPCs in short form) was systematically studied. The results indicate that HDPE‐g‐MAH as a compatibilizer can effectively promote the interfacial adhesion between GF/WF and HDPE. By the incorporations of GF/WF, the heat deflection temperature can reach above 120°C, and the water absorption can be below 0.7%, also the tensile strength, flexural strength, and impact strength of GWPCs can surpass 55.2 Mpa, 69.4 Mpa, and 11.1 KJ/m², respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of chemical modification of wood flour on the rheological properties of high‐density polyethylene blends

Chemical modification of lignocellulosic fibers can improve interfacial adhesion and dimensionally stabilize the resulting plastic composites. This study examined the rheological properties of wood flour/high density polyethylene (HDPE) melts after poplar wood flour was modified with glutaraldehyde (GA, mainly cell wall cross‐linking) and 1,3‐dimethylol‐4,5‐dihydroxyethyleneurea (DMDHEU, mainly poly‐condensation). Results show improvement in both the dispersibility of treated wood flour in the HDPE and its interfacial compatibility. Treatment with GA decreased melt viscosity, moduli, and shear stress as evidenced by rheometry. However, the modifying effects of DMDHEU were not observed, which was mainly due to reduced HDPE content. This study indicates that chemical modification of wood flour is a promising approach to improve the processability of highly filled wood thermoplastic composites via extrusion/injection molding processing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41200.     

Rheological behavior and mechanical properties of sawdust/polyethylene composites

We have characterized the melt rheological behavior and the solid tensile properties of sawdust/polyethylene composites prepared in an internal mixer. Various concentrations (from 0 to 60 wt %) and three particle sizes have been tested, in presence of a coupling agent (maleic anhydride grafted polyethylene). In the molten state, for each particle size, a mastercurve of the complex viscosity as function of frequency can be plotted, using a shift factor depending on weight fraction. We show that the shift factors can be described by a Krieger‐Dougherty law, leading to a “universal” viscosity law of the Carreau‐Yasuda type. In the solid state, the presence of sawdust increases Young modulus in uniaxial elongation, mainly for small size particles, but reduces dramatically deformation at break and tensile strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheological properties of linear low density polyethylene/polypropylene blends. Part 2: Solid state behavior

This second paper of a series continues the examination of the tensile properties of two series of linear low density polyethylene/polypropylene, (LLDPE/PP) blends. The blends were prepared using a twin-screw extruder and cover the whole concentration range, An Instron Universal Tensile Tester was used to measure the tensile properties of the blends between 10 and 70°C, and the temperature and composition dependences of the modulus were examined. A comparison is established between the solid state and melt properties to underline the behavior in the PP rich region. Results of dynamic mechanical experiments and differential scanning calorimetry on the same materials are also given, and the mechanical behavior is discussed in terms of the variation of the system's crystallinity.     

Dynamic mechanical properties of polystyrene/low density polyethylene blends

The dynamic mechanical properties of polystyrene/low density polyethylene blends and of polystyrene/polyethylene/di-block polystyrene-polyethylene copolymer blends have been investigated in the temperature range −160°C to +100°C. It is shown that anomalies in the low temperature shear modulus data of polystyrene-polyethylene blends are a consequence of non-adhesion between the components. From similar data of blends containing a partial di-block PS-PE copolymer it appears that only very small amounts of copolymer are needed to ensure adhesion between the polystyrene and polyethylene phase. Further it is shown that for modulus considerations of the blends, LDPE together with partial PS-PE copolymer can be treated as a single phase. In some cases the presence of copolymer causes formation of a continuous network throughout the polystyrene matrix, as reflected by a low value for the shear modulus of these blends. Phase reversal of polystyrene-polyethylene blends results in an increase of the loss modulus at 40°C which is ascribed to an increased friction caused by phase entanglements. This increase is more pronounced if an excess of polyethylene is present which is again a consequence of non-adhesion between the components.     

Barrier properties of polyamide-6/high density polyethylene blends

SUMMARY The barrier properties of Polyamide-6 (PA6)/High Density Polyethylene (HDPE) blends with and without compatibilizer prepared by ribbon extrusion were studied. The results show that the toluene diffusivity was improved by the addition of an interfacial agent and by inducing orientation of the polymer chains. The presence of PA-6 in the blend results in a decrease of the toluene diffusivity. This reduction is even larger for the case of the interfacial modified system. However, the most important reduction of the toluene diffusivity is observed for pure HDPE when stretched. A six-fold decrease is observed when the draw ratio is increased two fold. In the case of the permeability of different solvents through blends a gravimetric permeation cell was used. The results show that the permeability decreases with increasing size of the penetrant molecules (CH₂Cl₂, CHCl₃ and CCl₄) and this decrease is more important for a compatibilized blend. Received: 1 December 2000/Revised version: 21 March 2001/Accepted: 21 March 2001     

Thermal and mechanical characterization of linear low‐density polyethylene/wood flour composites

A linear low‐density polyethylene (LLDPE) matrix was modified with an organic peroxide and by a reaction with maleic anhydride (MAn) and was simultaneously compounded with untreated wood flour in a twin‐screw extruder. The thermal and mechanical properties of the modified LLDPE and the resulting composites were evaluated. The degree of crystallinity was reduced in the modified LLDPE, but it increased with the addition of wood flour for the formation of the composites. Significant improvements in the tensile strength, ductility, and creep resistance were obtained for the MAn‐modified composites. This enhancement in the mechanical behavior could be attributed to an improvement in the compatibility between the filler and the matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2775–2784, 2003     

Analysis of mechanical,thermal, and morphological behavior of polycaprolactone/wood flour blends

In the present study, the properties of polycaprolactone (PCL) and wood flour (WF) blends were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), Instron mechanical tester, and scanning electron microscopy (SEM). As for results, the mechanical properties of PCL were lowered obviously, due to the poor compatibility between the two phases, when it was blended with wood flours. A fine dispersion and homogeneity of wood flour in the polymer matrix could be obtained when the acrylic acid grafted PCL (PCL‐g‐AA) was used to replace PCL for manufacture of blends. This better dispersion is due to the formation of branched and crosslinked macromolecules since the PCL‐g‐AA copolymer had carboxyl groups to react with the hydroxyls. This is reflected in the mechanical and thermal properties of the blends. In comparison with pure PCL/WF blend, the increase in tensile strength at break was remarkable for PCL‐g‐AA/WF blend. The PCL‐g‐AA/WF blends are more easily processed than the PCL/WF ones since the former had lower melt viscosity than the latter. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1000–1006, 2004     

The morphology,rheological, and mechanical properties of wood flour/starch/poly(lactic acid) blends

An entirely biosourced blend composed of poly(lactic acid) (PLA), starch, and wood flour (WF) was prepared by a co‐extruder with glycerol as a plasticizer. The morphology, rheological properties, and mechanical properties of the WF/starch/PLA blends were comprehensively analyzed. The results showed that with the decrease of the starch/WF ratio, the morphology experienced a large transformation, and the compatibility of the blends was found to be superior to other blends, with a starch/wood flour ratio of 7/3. The dynamic mechanical thermal analysis (DMA) results demonstrated the incompatibility of the components in WF/starch/PLA blends. Following the decrease of the starch/WF ratio, the storage modulus (G″) and the complex viscosity (η*) of the blends increased. The mechanical strength first increased, and then decreased with the increase of the WF concentration. The water absorption results showed that the water resistance of the blends was reduced with the lower starch/WF ratio. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44743.     

Rheological and mechanical properties of ternary blends of linear-low-density polyethylene/polypropylene/ethylene-propylene block polymers

The effect of addition of an ethylene-propylene block polymer on rheological and mechanical properties of a linear-low-density polyethylene/polypropylene blend was examined. The samples were prepared by melt blending in a twin-screw extruder followed by injection molding. The single-, two- and three-component systems were treated the same way. The mechanical behavior of the blends was evaluated by means of tensile, and flexural, tests at 23 and ?40°C. The capillary, elongational, and dynamic-flow measurements were performed at 190°C.     

凝胶丁腈共聚弹性体增韧聚甲醛的加工流变行为及力学性能

研究了聚甲醛(POM)/凝胶丁腈共聚弹性体(GNBE)共混物的熔体流动指数(MFI)、高压毛细管流变行为和力学性能。结果表明,共混物MFI随GNBE用量的增加下降较大。聚酰胺(PA)对POM/GNBE共混体系的MFI影响较小,而热塑性酚醛树脂(PFR)的影响显著。当PFR的质量份为4时,POM共混物的MFI达最小值(0.053g/min),约为未加增容剂POM共混物MFI的1/6。随着剪切速率的提高,共混物剪切黏度迅速与POM接近。这种黏度变化行为说明共混物比GNBE对剪切速率更敏感,共混物的黏度受POM的影响较大。随着剪切速率的提高,POM与GNBE的黏度比迅速减小,并接近1,说明POM和GNBE在高剪切速率下共混时,GNBE的液滴能够在POM连续相中分散达到最小。含20份GNBE的POM共混物在高剪切速率下的熔体表观黏度与POM相当;在PFR质量份为6时,POM共混物的缺口冲击强度达到21.6kJ/m2,超过了GNBE质量份为40的POM共混物。当PFR质量份为4时,共混物的缺口冲击强度为对应的不加增容剂共混物的冲击强度的2倍多,扯断伸长率提高了55.4%。     

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.     

Effect of EPDM on the mechanical properties of blends of high and low density polyethylene

Summary We studied the effect of adding ethylene-propylene-diene rubber (EPDM) to blends of high (HDPE) and low (LDPE) density polyethylene. The extrusion torque of the blend without EPDM shows a deviation from the linear addition rule, but blends with rubber follow the addition rule. Two composition regions that are compatible with the torque behavior are present in the Young's modulus and extension at break curves. The EPDM content improves the extension at break of LDPE rich blends. This improvement extends to higher compositions of HDPE as the EPDM content is increased. Received: 4 September 1997/Revised version: 30 April 1998/Accepted: 13 May 1998