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采用杨木纤维与聚乳酸(PLA)粉末共混压制成一种新型生物质复合材料,以不同升温方式对纯PLA板材及其复合材料进行冷结晶,并通过示差扫描量热仪(DSC)、偏光显微镜(POM)、扫描电子显微镜(SEM)和万能力学试验机等对其进行测试和表征。结果表明:通过冷结晶方法,纯PLA板材和复合材料的结晶度分别由6%和18.3%提高到50%左右,两者的密度和冲击强度没有发生明显变化;但是复合材料弯曲强度和模量分别下降了约30%和16%,纯PLA板的弯曲强度也有一定程度的下降。通过SEM对复合材料微观结构进行表征,发现力学强度的下降是由于结晶后的PLA基体与木纤维之间的界面相容性变差造成的。通过POM观察冷结晶过程,发现纯PLA板及其复合材料形成大量的微小晶体,导致两者的透明性下降,因此,调控晶体结晶度有望成为改变PLA材料透明性能的新方法。
A kind of new biomass composite material was prepared by blending poplar fiber and polylactic acid (PLA) powder, cold crystallization of pure PLA sheet and its composite material was carried out by different heating methods, and the properties of the pure PLA sheet and its composite material were analyzed by differential scanning calorimeter (DSC) Microscope (POM), scanning electron microscopy (SEM) and universal mechanical testing machine, etc. were tested and characterized. The results show that the crystallinity of pure PLA sheet and composite increases from 6% and 18.3% to about 50%, respectively, by cold crystallization. The density and impact strength of the pure PLA sheet and the composite have not changed obviously. However, the flexural strength and modulus Respectively, down about 30% and 16%, bending strength of pure PLA board also has a certain degree of decline. SEM was used to characterize the microstructure of the composites. It was found that the decrease of mechanical strength was caused by the poor interfacial compatibility between the crystallized PLA matrix and wood fiber. Through the POM observation of the cold crystallization process, it was found that the pure PLA plate and its composite material formed a large number of tiny crystals, resulting in a decrease of the transparency of the two. Therefore, adjusting the crystallinity of the crystal is expected to become a new method for changing the transparency of the PLA material.