利用弹性体增韧木粉/HDPE复合材料
Improve toughness of wood flour/HDPE composites with elastomers

为提高木塑复合材料的韧性,在木粉/高密度聚乙烯(WF/HDPE)复合材料制备过程中引入了3种弹性体:聚烯烃弹性体(POE)、弹性体改性聚乙烯(BPB)和接枝改性的聚烯烃弹性体(A669)。通过对WF/HDPE复合材料冲击强度和抗弯弹性模量的测试,确定出既能有效提高WF/HDPE复合材料韧性又能维持材料刚性的增韧剂种类及其用量,并通过结晶行为、热力学性能及界面结合分析等探讨了其增韧原理。通过对比可知, A669的增韧效果最为明显,质量分数为4%时冲击强度达到15.31 kJ/m2,相对于无添加配方提高了52.34%且抗弯弹性模量只下降6.09%。XRD和DSC分析结果表明:A669的添加阻碍了WF/HDPE复合材料的结晶行为,使其在略低的温度下才可以结晶,且结晶度下降,晶粒尺寸增大,衍射角所对应的衍射面增大,因此吸收和损耗了更多的能量;A669的添加还降低了WF/HDPE复合材料的玻璃态转变温度。DMA和SEM分析结果显示:A669的添加使WF/HDPE复合材料呈现出显著的黏性特征,断裂面的HDPE塑料基质出现拉丝现象,从而达到提高材料韧性的效果。转矩流变测试表明A669的添加使WF/HDPE复合材料的扭矩略有降低,对加工没有不利影响。适当添加A669可以使木塑复合材料同时具备良好的韧性和刚性,对扩大其在建筑模板等领域的应用具有重要意义。 Three kinds of elastomers, polyolefin elastomer (POE), elastomer modified polyethylene (BPB) and graft modified polyolefin elastomer (A669) were introduced to preparation process of wood flour/high density polyethylene (WF/HDPE) composite to improve the toughness of wood-plastic composites. The kinds and contents of toughening agent at which can simultaneously improve the toughness and maintain the rigidity of WF/HDPE composites were determined by the impact strength and flexural elastic modulus test of WF/HDPE composites. The toughening principles were analyzed by the aid of the crystallization behavior, thermal dynamic property and interface bonding analysis. Through comparison, it shows that A669 is the most effective one; when adding mass fraction is 4%, the impact strength is 15.31 kJ/m2, increases by 52.34% comparing to the composite without A669, while the flexural elastic modulus just decreases by 6.09%. XRD and DSC analysis results show that, adding A669 hinders the crystallization behavior of WF/HDPE composites, which decreases the crystallization temperature and the crystallinity, while increases the grain size and the size of the diffraction surface corresponding to the diffraction angle. Thus more energy is absorbed and lost, and the glass transition temperature of WF/HDPE composite decreases. The DMA and SEM analysis results show that, the WF/HDPE composites with A669 present more viscosity characteristic, and the wiredrawing phenomenon of plastic matrix appears on the fracture surface, improving the toughness of the material. The torque rheometer test shows that, the balance torque of WF/HDPE composites does not change significantly, which indicates that A669 will not adversely affect the processing. Therefore, A669 can provide wood-plastic composite with both good toughness and stiffness under an appropriate use level. The results of present study will greatly promote the application of wood-plastic composite in building templates etc.