Mechanical,Thermal and Morphological Characterization of High-Density Polyethylene and Vermiculate Composites

High-density polyethylene composites containing 7, 10, 15 and 20% w/w vermiculite (VMT) were prepared by extrusion in a twin-screw extruder at various shear rates. The thermal and mechanical properties and morphological characteristics of the composites were evaluated and compared with pure high-density polyethylene. The blend morphologies were determined by scanning electron microscopy (SEM). The thermal properties of the composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The TGA results reveal that the use of VMT particles to fill polyethylene increased the thermal stability of the composite. The results obtained indicate that a shear speed of 400 rpm and vermiculite content of 7% showed the best properties of impact resistance. These observations were confirmed by morphology analysis.     

麻纤维增强聚乙烯复合材料的制备及性能研究

通过双螺杆挤出造粒,注塑成型制备了麻纤维增强高密度聚乙烯( HDPE)复合材料,测试了复合材料的力学性能并观察其微观结构,分析了相容剂马来酸酐接枝聚丙烯( PP-g-MAH)的用量和麻纤维的含量对复合材料力学性能的影响.结果表明:PP-g-MAH的加入提高了苎麻/HDPE复合材料的力学性能,并且在PP-g-MAH含量为...     

高密度聚乙烯／废橡胶胶粉共混物的改性研究

采用新的改性体系三元乙丙橡胶（EPDM）、硅油、过氧化二异丙苯（DCP）对高密度聚乙烯／胶粉（HDPE／SRP）共混物进行了研究，探讨了各改性剂用量对共混物力学性能的影响。结果表明：EPDM用量为10－15份，硅油用量为4份，DCP用量为0.2份，共混物具有较好的力学性能。与未改性HDPE／SRP共混物相比，改性后共混物（EPDM为10份，硅油为4份，DCP为0.2份）的冲击强度和断裂伸长率分别可以大幅度提高，并且胶粉含量越少，提高的幅度越明显。扫描电镜观察结果表明：改性共混物中弹性体的分散和包覆结构是韧性提高的主要原因。     

Effects of Defibration Conditions on Mechanical and Physical Properties of Wood Fiber/High-Density Polyethylene Composites

Defibration conditions influence wood fiber characteristics and thereby properties of fiber-based materials. In this study, the effects of several defibration conditions on mechanical and physical properties of fiber-based wood-plastic composites (WPCs) are illustrated. Various WPCs were tested containing different thermo-mechanical pulps (TMPs) or groundwood pulp (GWP), whereby material composition (50 wt% wood fibers, 47 wt% polymer, 3 wt% coupling agent) and the production process (internal mixer, injection molder) were kept consistent. The data from the experiment revealed that differing defibration conditions led to statistically significant differences in the tested flexural, tensile, and impact properties as well as in the water absorption of WPC. Overall, the GWP and the TMP which was produced under the mildest defibration conditions performed best in fiber-based WPCs. Therefore, grinders and refiners may be equally suitable to produce pulp for WPC usage. As a side-effect within this study, the reinforcing effect of fiber application on flexural and tensile properties was on an extraordinarily high level.     

Physical and Mechanical Properties of Iron Powder Filled Polystyrene Composites

This article reports on an experimental study of the physical and mechanical properties of Polystyrene (PS) and Fe-PS polymer composites containing 5, 10, and 15 vol.% of Fe powder. After mixing Fe powder and PS in a twin-screw extruder, an injection-molding machine was used to prepare unfilled PS and Fe-PS polymer composite samples. After that, the material properties were experimentally determined for each sample. The investigated material properties included the modulus of elasticity, yield and tensile strength, % elongation, Izod impact strength (notched), hardness (Shore D), melt flow index (MFI), heat deflection temperature (HDT), Vicat softening point, and glass transition temperature (T _g ). The results indicated that, compared to the unfilled PS, an addition of Fe into PS decreases the yield and tensile strength, % elongation, and Izod impact strength. Furthermore, it was determined that the Fe particles increase the modulus of elasticity, hardness, MFI, Vicat softening point, and HDT values.     

Preparation and Characterization of Partially Degraded High-Density Polyethylene in an Internal Mixer

The partial degradation of high-density polyethylene was done in an internal mixer for different residence time. The oxidative thermomechanical degradation resulted in the formation of carbonyl groups in the polymer. The carbonyl index values estimated from the FTIR studies indicate the increase of carbonyl groups without any induction time. The common phenomenon during oxidative degradation of polyethylene is the increase in trans-vinylene groups and decrease in vinyl groups and these phenomena are observed in the current investigation. Owing to the chain scission occurring during the mixing at processing temperature, the change in morphology was studied by the amount of crystallinity estimated through DSC. The variation in the molar mass of the material was followed by SEC method.     

Effect of Metallocene-Catalyzed Polyethylene on the Physicomechanical Properties of Blends with High-Density Polyethylene or Low-Density Polyethylene

The physicomechanical properties of polymer blend formulations comprising different grades of metallocene-catalyzed linear low-density polyethylenes (mLLDPEs) with high-density polyethylenes (HDPEs) or a low-density polyethylene (LDPE) were investigated. For blends with HDPE, the addition of mLLDPE improves the Izod impact strength and some tensile properties. For blends with LDPE, adding mLLDPE increases the ductility and the percent elongation at break.     

Influence of Alumina Particles on Thermal Behavior of High Density Polyethylene (HDPE)

This study evaluated the effects of alumina (Al₂O₃) particles on thermal properties of High Density Polyethylene (HDPE). HDPE and HDPE/5, 10 & 15 wt% Al₂O₃ composites were prepared by compression molding. Differential scanning calorimetery (DSC) was used to analyze the thermal and crystallization behavior of the samples. The results indicated that the alumina particles affected the crystallization behavior of HDPE matrix, significantly. However, the DSC results showed that alumina content did not influence the melting temperature of HDPE in this composite. The results also showed that the incorporation of alumina particles caused the decrease of specific heat capacity coefficient and entropy.     

Mechanical,Thermal and Morphological Properties of Grewia Optiva Fiber/Polymer Matrix Composites

This work is concerned with the evaluation of properties of compression molded Grewia Optiva fiber reinforced Resorcinol-Formaldehyde (RF) matrix-based polymer composites. Reinforcing of the RF resin with Grewia Optiva fiber was done in the form of particle size (200 micron). Present work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength and wear resistance of the RF matrix have been found to increase up to 30% fibre loading (in terms of weight) and then decreases for higher loading. Morphological and thermal studies of the matrix, fibre and particle reinforced (P-Rnf) green composites have also been studied.     

Mechanical and dynamic mechanical properties of waste rubber powder/HDPE composite

Mechanical and dynamic mechanical properties of a waste rubber powder‐filled high‐density polyethylene (HDPE) composite are investigated. Rubber powder is surface‐modified with acrylamide (AAm) using ultraviolet. Rubber powder and HDPE are extruded using a single‐screw extruder and maleic anhydride‐grafted polypropylene is added as a compatibilizer to improve the adhesion between rubber powder and HDPE. The tensile stress and strain of AAm‐grafted rubber powder/compatibilizer/HDPE composites always exhibit higher values than those of unmodified rubber powder/HDPE composites. Surface modification of rubber powder is shown to decrease the magnitude of the tan δ of the HDPE composite. Higher values of the notched Izod impact strength of a surface‐modified rubber‐filled composite is observed compared to those of unmodified rubber‐filled composite. Experimental results show that acryl amide‐grafted rubber powder reacts with maleic anhydride and it results in improved mechanical properties of the HDPE composite. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2595–2602, 2000     

废弃天然纤维增强高密度聚乙烯复合材料性能研究

选用纺织工业废弃苎麻落麻纤维和造纸工业废弃的竹屑纤维为增强体,采用双螺杆熔融共混挤出工艺,制备天然纤维增强高密度聚乙烯（PE-HD）复合材料。考察纤维种类、含量变化对天然纤维增强复合材料熔体流动速率、微观断面形貌、拉伸性能、弯曲性能的影响。结果表明,2种废弃纤维都能有效提高PE-HD的拉伸性能和弯曲性能,其中苎麻落麻纤维的增强效果优于竹屑纤维,加入20% 苎麻落纤维复合材料拉伸强度比纯PE-HD提高21%,弯曲强度提高了41.9%。     

Effects of Rice Husk Filler on the Mechanical and Thermal Properties of Liquid Natural Rubber Compatibilized High-Density Polyethylene/Natural Rubber Blends

Natural rubber/high-density polyethylene (NR/HDPE) blend with rice husk (RH) filler and liquid natural rubber (LNR) as the compatibilizer was prepared using an internal mixer at 140°C and 50 rpm. The reinforcing effect and compatibilizing performance of the added reagents in the composites were evaluated from the mechanical and thermal properties, and blend homogeneity. The tensile and impact strength decreased with RH loadings in the matrix, while the tensile modulus and hardness showed an opposite trend. The weak filler–matrix interaction, resulting in poor filler dispersion and large agglomerated particle size, caused those properties to decrease. However, the mechanical properties of the composites improved with the addition of NR or LNR into the matrix. The dissolution effect caused interactions between the phases, leading to an improvement in the compatibility in the blend. Changes in morphology resulted in the shift of T _g of the amorphous part of NR to higher temperatures, as observed in differential mechanical analysis (DMA) thermograms. Scanning electron microscopy (SEM) micrographs of the fractured surface had also revealed the good RH–matrix interaction and, thus, the dispersion of particles in samples with added LNR.     

Weathering of High-Density Polyethylene-Wood Plastic Composites

Due to the widespread use of wood-plastic composites (WPCs), high-density polyethylene-wood flour composites (HDPE/WF) were studied in order to determine their stability in different application conditions. UV degradation and periodic absorption/desorption of moisture cause damaging changes to material during WPCs’ exterior application, so it is necessary to ensure WPCs’ durability against atmospheric influences. Samples were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) in order to study the degradation after simulated weathering. The degree of water absorption was also determined. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used for the determination of composites’ thermal properties. Results show that the stability of the HDPE/WF composites to UV treatment highly depends on stabilizer content and its dispersion in the polymer matrix. Incompatibility of HDPE and wood particles is a major problem that should be solved to achieve good durability and satisfying properties in use.     

Cavitation in Irradiated and Oriented High-Density Polyethylene Cast Films with Stacked Lamellar Morphology

Cavitation (void formation) in high-density polyethylene cast films, having a stacked lamellar morphology, subsequent to tensile stretching of both nonirradiated and irradiated films was investigated. With nonirradiated films, the cavitation was not observed in the nonannealed films with lower draw ratios, while a limited number of voids was detected in the films of higher draw ratios. Annealing caused an intensive cavitation, and uniform distribution of cavities was noticed in highly oriented films. It was shown that cross-linking exerted a suppressive influence on cavitation in the annealed and oriented films; and with increasing the irradiation dose, the cavitation was completely eliminated.     

Compatibilization Effects of PE-g-MA on Mechanical,Thermal and Swelling Properties of High Density Polyethylene/Natural Rubber/Thermoplastic Tapioca Starch Blends

Effect of polyethylene grafted maleic anhydride (PE-g-MA) on mechanical, thermal and swelling characteristic of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends were studied. The measurements from differential scanning calorimetric (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), proved the effectiveness of PE-g-MA as compatibilizer in improving the miscibility between HDPE/NR – TPS blends. A decrement in crystallinity index was found after adding PE-g-MA. It is due to restriction in mobility of the HDPE chains. In the presence of PE-g-MA, the blends have better thermal stability. On top of that, the storage modulus which is reflected to the blend stiffness also increased as indicated the improvement in HDPE/NR – TPS interaction.     

Influence of the Interphase on Impact Properties of Zirconium Silicate Filled High-Density Polyethylene

Yellow zirconium silicate is a promising substitute for cadmium pigments used in plastics. However, the incorporation of zircon pigment in HDPE without loss of impact strength is required. By introducing the untreated pigment in the polymer, the impact strength reduces to 60% of the value for the unfilled polymer. Different types of silane coupling agents were used to regain the impact strength of the composite. Octadecylsilane acted as a wetting agent rather than as a coupling agent. The impact strength hardly improved. A vinyl functional and a methacryloxy functional silane improved the impact strength to 70% relative to the unfilled polymer. The physically bonded, interdiffused network formed by silane and polymer improves the impact strength by the flexible nature of the interphase. An azidosilane improved the impact strength only to 73%: the interphase bonded covalently to the polymer as well as to the filler, in that way improving the impact strength, but behaving as a brittle system. A relatively thick, flexible interphase bonded covalently to filler and polymer was created. This interphase improved the impact strength to the value of the unfilled polymer.     

注射成型短碳纤维增强聚乙烯复合材料力学性能的研究

研究了碳纤维含量对注射成型高密度聚乙烯/碳纤维复合材料拉伸强度、硬度和弹性模量的影响。结果表明,随着碳纤维含量的增加,复合材料的硬度、弹性模量和拉伸强度逐渐增大;当碳纤维含量小于3.3 %时,复合材料的硬度、弹性模量和拉伸强度成线性增加趋势;当碳纤维含量大于3.3 %时,复合材料的硬度、弹性模量和拉伸强度的上升趋势增大。     

木粉和抗氧剂对废旧PE-HD/沙柳复合材料性能的影响

以沙柳木粉和废旧高密度聚乙烯（PE-HD）为原料,采用模压法制备了木塑复合材料（WPC）。考查了沙柳木粉和抗氧剂对WPC性能的影响。结果表明,沙柳木粉加入量为0~70 %（质量分数,下同）时,WPC的静曲强度呈先上升后下降的趋势,弹性模量和拉伸强度分别呈上升和下降的趋势;沙柳木粉降低了WPC的热稳定性,使热分解起始温度降低;随加入量的增加,WPC的储能模量（E′）和损耗模量（E″）曲线均呈上升趋势,损耗因子（tanδ）曲线呈下降趋势,E″曲线内耗峰的位置向高温方向移动;抗氧剂1010加入量为0~0.5 %时,WPC的静曲强度、弹性模量和拉伸强度均呈不同程度的先上升后下降的趋势;当抗氧剂加入量为0.2 %和0.3 %时,E′和E″相对较高。     

Study of Hybridized Kenaf/Palf-Reinforced Hdpe Composites by Dynamic Mechanical Analysis

This article presents an experimental study on the dynamic mechanical property of hybridized Kenaf/PALF-reinforced HDPE composites. Variation in storage modulus (E′), loss modulus (E″) and damping parameter (tan δ) with fiber loading and variation in fiber length were investigated. The concept of hybridization was also discussed as it affects the dynamic properties. Initial storage modulus (E′) of all hybrids at different fibre ratios have been enormously improved compared to pure HDPE, and dependence of modulus on cellulose content of natural fibres was very clear. A lower percentage of PALF is required for hybridization with kenaf bast fibre to achieve a positive hybridization effect. Adequate hybridization could impart higher impact strength to the composite. The dynamic modulus curve showed an increase in the E′ value with increase in operating temperature up to about 130°C and is at a maximum at higher fibre loading. At lower temperatures, 60% of fibre loading had reduced the loss modulus peak of the pure HDPE. At temperature range of 30 to 65°C, incorporation of the fibres helped reduce the E″ peak of the matrix. Increasing the fibre content of the hybrids raised the damping peak with temperature. In addition, there is an increase in storage modulus with increased fibre length at room temperature up to about 65°C. Above this temperature, variation in fibre length became irrelevant up to the less viscous point of the matrix. A marginal difference in loss modulus with variation in fibre length was observed, no difference could be seen in the case of loss tangent (tan delta) in regard to variation in fibre length.     

Thermal Sensor to Monitor Mechanical Properties in Polymer/Fiber Composite Molding

Multi‐layered samples of 1) continuous fiber axially aligned and 2) random oriented mat glass fiber composites were manually prepared for a fiber content ranging from zero to 20% (vol.). The uniaxially aligned samples displayed linear relations between both normalized elastic modulus and normalized thermal conductivity, and fiber content, for axially applied load and heat flux. For the random mat composite samples, similar results were obtained, with symmetry displayed in the plane of the mat. In both cases, measured axial thermal conductivity permits an evaluation of the axial elastic modulus. The Mathis surface probe used (US patent #5,795,064) is demonstrated as a non‐intrusive indirect method of obtaining thermal conductivity for heat flux parallel (i.e. axial or transverse) to the plane of a sample. The method shows potential for use as an in‐line monitoring device for the mechanical properties of molded composites.