In the present study, lithium chloride (LiCl) was utilized as a modifier to reduce the melting point of polyamide 6 (PA6), and then 15 wt % microcrystalline cellulose (MCC) was compounded with low melting point PA6/high-density polyethylene (HDPE) by hot pressing. Crystallization analysis revealed that as little as 3 wt % LiCl transformed the crystallographic forms of PA6 from semi-crystalline to an amorphous state (melting point: 220 °C to none), which sharply reduced the processing temperature of the composites. LiCl improved the mechanical properties of the composites, as evidenced by the fact that the impact strength of the composites was increased by 90%. HDPE increased the impact strength of PA6/MCC composites. In addition, morphological analysis revealed that incorporation of LiCl and maleic anhydride grafted high-density polyethylene (MAPE) improved the interfacial adhesion. LiCl increased the glass transition temperature of the composites (the maximum is 72.6 °C).
In this work, the statistical distribution of mechanical properties and energy absorption at break of laminated cotton fabric reinforced epoxy composites was determined. The static mechanical tests showed that the cotton fabric significantly influenced the mechanical performance of epoxy resin, where tensile strength, tensile modulus, tensile elongation at break, flexural modulus, and impact strength increased significantly, while flexural strength decreased. The energy absorption behaviors in the tensile tests were investigated, where more energy at tensile break was absorbed when cotton fabric was incorporated, as shown by the 684% to 2707% increase. The similar increases were observed in the flexural and impact tests, which were 92% to 355% and 309% to 833%, in different directions, respectively. The statistical distribution patterns of the mechanical properties parameters in variously direction of cotton fabric reinforced laminate were mapped. The results showed the distribution patterns of tensile modulus, flexural modulus, tensile strength, flexural strength, and energy absorption before maximum stress in the flexural test correlated with fiber angle in the laminate, while the distribution patterns of tensile elongation, impact strength, and energy absorption in the flexural and tensile tests agreed well with distribution of fiber content in the test cross section. With the incorporation of cotton fabric, the breakage behavior of epoxy transitioned from brittle fracture to toughened fracture as shown in distribution patterns of fracture energy absorption. The viscoelastic properties of the cotton fiber‐reinforced laminates were investigated via DMA. The cotton fiber‐reinforced laminates possessed higher transition temperatures, the storage modulus (E') and loss modulus (E"), compared to epoxy.
Polypropylene (PP) modified with two reactive monomers, divinyl benzene (DVB) and maleic anhydride (MAH), was used as the matrix to prepare wood-polypropylene composites to improve interfacial compatibility. The effects of the co-modified PP matrices with different DVB concentrations on the mechanical properties of the composites were evaluated. Compared with unmodified composites and the composites containing a coupling agent, the composites modified with MAH only, and that with both MAH and DVB, improved the tensile, flexural, and impact strengths. Interestingly, adding a small amount of DVB (0.4%) resulted in significant increase in impact strength, relative to that of the composites modified with MAH only. Dynamic mechanical analysis and fracture morphology analysis of the modified composites also suggested an improvement in interfacial adhesion owing to the matrix modification.
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