皮层对皮-芯结构木塑复合材料性能的影响

Effect of shell on core-shell structure wood polymer composite with short glass fiber filled shells via co-extrusion technology

【目的】研究在两种不同芯层材料的复合体系下,增强材料含量与皮层厚度对共挤出(皮-芯结构)木塑复合材料弯曲与热膨胀性能的影响。【方法】以共挤出技术为加工工艺,选取短玻璃纤维(SGF)为皮层的增强材料,制备共挤出型(皮-芯结构)木塑复合材料(WPC)。分析了在芯层1与芯层2两种复合体系下,不同皮层厚度(1.0、1.2及1.6 mm)和皮层填料含量(0%、10%、20%、30%和40%)对共挤出型皮-芯结构WPC的弯曲性能和热膨胀性能的影响。【结果】当表面为纯的高密度聚乙烯(HDPE)时,在芯层1和芯层2两个复合体系中,皮层越厚则复合材料的热膨胀系数(LTEC)越高,其热膨胀性能越差;当SGF的加入量恒定时,其LTEC随着皮层厚度的增加而降低。当皮层的弯曲模量比芯层低时,共挤出木塑复合材料的弯曲模量随着皮层厚度的升高逐渐降低;当芯层的弯曲模量比皮层低时,共挤出木塑复合材料的弯曲模量随皮层厚度的升高而升高。皮层为SGF/HDPE材料时,在芯层1和芯层2两个复合体系中,随着皮层SGF的含量从0%增加到40%时,其弯曲性能显著性提高,LTEC显著降低。当皮层的LTEC值比芯层大时,皮层厚度的降低可以降低共挤出木塑复合材料的LTEC;当皮层的LTEC值小于芯层时,共挤出木塑复合材料的LTEC随皮层厚度的增加而减少。【结论】通过改性芯层可以提高皮-芯结构木塑复合材料的整体性能,其增强趋势与表层的增强趋势相似。

[ Objectives] In order to investigate the effects of various GF contents in the shell layer and shell thickness changes on thermal expansion and flexural properties of coextruded WPCs. [ Methods ] Co-extruded WPCs with short glass-fiber （SGF） loaded shells were manufactured, the formulations for the two-core systems and three shell thicknesses （i.e., 1.0, 1.2 and 1.6 mm） were used to make different shells. Their flexural and thermal expansion behavior was studied. It was shown that the LTEC values varied with composite structure and composition （i.e., core, shell thicknesses and materials）. [ Results ] The use of SGF-filled shells helped lower overall composite LTEC values. The imbalance LTEC between core and shell layer, and their modulus caused complex stress fields within a given composite system. Ex- truding a relatively thick, less-stiff HDPE shell with a large LTEC value over a stiff and thermally. Stable WPC core de- creased overall composite modulus and increased the LTEC values. The composite modulus and strength increased and LTEC values decreased with increase of the SGF loading levels in the shell. [ Conclusions] The flexural modulus/strength of core-shell structure WPC was greatly enhanced with unfilled-and filled HDPE shells.