| Bamboo-fiber filled polymer composites is an environment-friendly materials, which makes full use of the abundant resources of bamboo in China. Blending with thermoplastic polymer, bamboo/plastic composites possess the advantages of bamboo fiber and polymer, being able to substitute pure plastic products, favorable solving environment problem. Bamboo is widely distributed in China. Due to some excellent properties such as fast growth, high strength and hardness, fiber content in bamboo, bamboo fiber has become a low-price and high-performance fillers in polymer blending. However, the lower compatibility of bamboo fibers (BF) and the resin matrix results in the lower mechanical behavior of bamboo/plastic composites, which restricts the application of material. Nylon 6(PA6) is an important engineering plastics, which is widely used in the automotive industry, electrical and electronic products and household electrical products. However, widely application of PA6 products is restricted by poor impact strength in low temperature, lack of performance after absorbing moisture and high cost of PA6, especially when a large amount of fillers is added into the PA matrix.Due to poor compatibility between the bamboo fiber and nylon 6 resin in the BF/PA6 composite, alkali treatment of the bamboo fiber was carried out, and the effects of alkali treatment on morphology and construction of bamboo fiber were investigated in detail. The better processing parameters (10wt% NaOH solution for 24h) were obtained for the alkali treatment of the bamboo fibers. The results showed that BF provided a larger surface area for leaching out the cementing materials during alkali treatment, which could improve the mechanical interlocking between bamboo fiber and the PA6 matrix. In addition, crystallinity of bamboo fiber due to alkali treatment was improved, which may enable the bamboo fiber/PA6 composites to have better performance.In order to improve the toughness of PA6 and BF/PA6 composites, and enhance the compatibility between the bamboo fiber and nylon 6 resin of the 30wt%BF/PA6 composite, ethylene-vinyl acetate copolymer (EVA), maleic anhydride grafted ethylene-octene copolymer (POE-g-MAH), maleic anhydride-grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) as a modifier, were blended with PA6 and 30wt%BF/PA6. The combination of BF, toughening modifier and PA6 may enable the composite to have the advantages of the three components:enough stiffness and toughness, lower costs and absorption of water. Therefore, BF/PA6, EVA/PA6, POE-g-MAH/PA6, EVA-g-MAH/PA6 binary composites and 30wt% BF/EVA/PA6,30wt% BF/POE-g-MAH/PA6,30wt% BF/EVA-g-MAH PA6 ternary composites were prepared by a twin screw extruder and injection molding machine, and analyzed by SEM, XRD, TG, DSC, FTIR and mechanical testing as well as absorption of water and Vicat softening temperature.Studies showed that the toughness of composites was improved by PA6 blending with EVA, POE-g-MAH and EVA-g-MAH. The notched impact strength of the EVA/PA6(8/92), POE-g-MAH/PA6(16/84) and EVA-g-MAH/PA6(12/88) were 18.2 kJ · m-2,35.4 kJ · m-2 and 20.1 kJ · m-2 respectively, which was higher that of pure PA6 (13.5 kJ · m-2). SEM results indicated that PA6 was miscible with lower level of EVA and EVA-g-MAH. However, with the content of toughening agent increasing, EVA and EVA-g-MAH appeared agglomeration, resulting in lower compatibility between PA6 and EVA or EVA-g-MAH. The stiffness and strength of PA6 increased with the addition of appropriate BF, however the toughness and processing ability of the BF/PA6 composite decreased significantly. The addition of appropriate EVA, POE-g-MAH, EVA-g-MAH blending with 30wt% BF/PA6 can improve the compatibility and enhance interfacial adhesion between BF and PA6, resulting in uniform dispersion of HA particles in the PA6 matrix, and increased toughness of 30wt% BF/EVA/PA6,30wt%BF/POE-g-MAH/PA6,30wt% BF/EVA-g-MAH/PA6 ternary composites. Compared with the notched impact strength (4.4 kJ · m"2) of 30wt%BF/PA6, the notched impact strength of BF/EVA/PA6 (30/8/62), BF/POE-g-MAH/PA6 (30/16/54), BF/EVA-g-MAH/PA6 (30/12/58) ternary composites increased to 8.1 kJ·m-2,8.5 kJ · m-2,7.5 kJ · m-2, respectively.TG results showed that the decreased thermal stability of PA6 of BF/PA6 composites by BF addition is counteracted by blending appropriate EVA, POE-g-MAH or EVA-g-MAH. DSC results showed that the dispersed BF inside the polymer matrix seemed to hinder the diffusion process, hamper crystal formation and resulted in more crystal imperfection compared with EVA, POE-g-MAH or EVA-g-MAH. EVA, POE-g-MAH or EVA-g-MAH provided a greater possibility for the growth of PA6 crystals and led to the formation of more perfect crystals.The results of water absorption showed EVA-g-MAH can more effectively reduce the water absorption of PA6 and 30wt% BF/PA6, compared with EVA and POE-g-MAH. Vicat heat distortion analysis showed that the heat distortion temperature of PA6 and 30wt% BF/PA6 was improved with lower levels of 4wt% EVA or EVA-g-MAH. However, when the content of EVA or EVA-g-MAH was further increased, the heat distortion temperature of PA6 and 30wt% BF/PA6 gradually decreased. |
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