聚氨酯预聚体改性聚乳酸/木粉复合材料的制备及表征

通过共混挤出法制备聚氨酯预聚体(PUP)改性的聚乳酸/木粉(PLA/WF)复合材料,并对复合材料进行力学性能测试、动态热机械分析、接触角测量以及断面扫描电镜分析。力学性能分析表明:当PUP用量(以PLA和WF的质量计)为20%时,复合材料断裂弯曲应变和冲击强度分别为5.78%和18.3 k J/m2,较未改性的复合材料分别提高了209%和123%,PUP显示出较好的增韧效果。动态热机械分析表明:随着PUP用量的增加,复合材料中PUP相和PLA相的玻璃化转变温度均有所下降,并且储能模量显著降低,材料韧性得到改善。PUP的加入可显著提高复合材料对水的接触角,材料疏水性能得到改善。当PUP用量为25%时,接触角达83.7°,较未增韧复合材料接触角(66.6°)提高25.7%。拉伸断面的扫描电镜分析表明:添加PUP的复合材料断面有更多的木粉被拉出且空穴变多,断面更为不平整,呈现韧性断裂的特征。

Preparation and Characterization of Poly(lactic acid)/Wood Flour Composites Modified with Polyurethane Prepolymer

Poly( lactic acid)/wood flour ( PLA/WF) composites modified with polyurethane prepolymer ( PUP) were prepared by blending extrusion, and followed by the test of their mechanical properties, dynamic mechanical analysis ( DMA) , contact angle measurements, and scanning electron microscope ( SEM) analysis on fracture surface. The mechanical property tests showed that flexural strain at break and impact strength of the composites containing 20 % PUP calculated by mass fraction of PLA and WF were 5. 78% and 18. 3 kJ/m2 which were 209% and 123% more than that of untreated sample, respectively. The results indicated that PUP had great effect on toughening the composites. DMA analysis revealed that with the increase of PUP. This two distinct glass transition temperatures corresponding to PLA and PUP phases all decreased, the storage modulus also decreased siginficantly and the toughness of the composites improved. The contact angle test towards water increased obviously with the addition of PUP. This showed the increse of hydrophobic performance. The contact angle of the composites reached to 83. 7° with 25% PUP and the value increased by 25. 7% comparing with that of non-toughened composites (66. 6°). SEM examination on the composite fractured surface showed more wood powder was pulled out and the section was more uneven with the addition of PUP. This presented the characteristic of ductile fracture.