Effect of Cold-Drawn Fibers on the Self-Reinforcement of PP/LDPE Composites
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JMEPEG DOI: 10.1007/s11665-017-2823-3
Effect of Cold-Drawn Fibers on the Self-Reinforcement of PP/LDPE Composites Ying-Guo Zhou, Bei Su, and Hai-Hong Wu (Submitted February 20, 2017; in revised form June 29, 2017) In our previous study, a method to fabricate super-ductile polypropylene/low-density polyethylene (PP/ LDPE) blends was proposed, and a fiber-shape structure was shown to be formed, presenting necking propagation during tensile testing. In this study, the mechanical properties and thermal behavior of the necking region of tested super-ductile PP/LDPE samples were carefully investigated and further compared with the melt-stretched, untested, and thermo-mechanical-history-removed samples by differential scanning calorimetry and tensile testing. The results suggest that the tested samples have high mechanical properties and are more thermo-mechanically stable than the common PP/LDPE blends and melt-stretched samples. Additionally, to investigate their structure-property relationship, the necking region of the tested samples was further characterized by scanning electron microscopy and hot-stage polarized light microscopy. It can be concluded that the variation of the microstructure can be attributed to the cold-drawn fibers (CDFs), which were more stable thermally, formed during the tensile test. Furthermore, the CDFs were used for the filler in PP/LDPE blends. The experimental results of the different PP/LDPE composites indicate that the CDFs are a good reinforcement candidate and have the ability to improve the mechanical properties of the PP/LDPE blends. Keywords
cold-drawn fiber (CDF), mechanical properties, necking region, PP/LDPE, self-reinforcement
1. Introduction Polypropylene (PP) and low-density polyethylene (LDPE) are both widely used common thermoplastic polymers because of their advantageous physical and processing properties. Mechanical blends of PP and LDPE have also become commercially important (Ref 1-5), which can possibly be attributed to cost considerations or special performance requirements. Generally, similarly to a copolymer, a polymer blend may exhibit properties departing from those of its homogeneous components. However, it has been shown in several studies that certain properties of the blends are better than those of the parent homopolymers, as observed in efforts to improve certain properties of PP/LDPE blends (Ref 6-21). These efforts can be roughly classified into four categories: (1) adding compatibilizers to improve the poor interfacial bond between the two phases (Ref 6-10), (2) utilizing fibers as reinforcements to produce PP/LDPE composite materials (Ref 11-13), (3) incorporating micro- or nanoparticles into the PP/ LDPE matrices (Ref 14-19), and (4) using special processing technology without any other filler (Ref 20, 21). It is well known that PP and LDPE are, despite the similarity of their chemical structures, immiscible and incompatible (Ref Ying-Guo Zhou and Bei Su, School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 21200
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