【作者】 张琪；

【导师】 杨冬芝；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2012， 硕士

【摘要】 聚乳酸（PLA）是一种来源于可再生资源的生物可降解材料，它具有广阔的市场前景，因此被认为是新世纪最有前景的生物医药材料和新型包装材料。除此之外，PLA被认为是可代替传统塑料的环境友好型材料。然而，脆性、耐热性差、抗冲击性差等缺点严重限制了聚乳酸在工程领域的发展，因此，对PLA的机械性能及热性能的改性成为目前研究的重点。本文主要针对PLA作为通用塑料应用存在的问题，采用共混改性的方法，以期获得具有使用价值的增强耐热聚乳酸材料，为加速推广应用完全生物降解聚乳酸材料奠定基础。通过天然纤维及蒙脱土分别对聚乳酸进行了改性，制备了PLA/天然纤维、PLA/蒙脱土复合材料，并借助万能材料试验机、动态力学分析仪、热失重分析仪、差示扫描量热仪、扫描电子显微镜、透射电子显微镜等手段分析了共混膜的机械性能、热稳定性、结晶性等。论文主要工作及取得的结果如下：（1）通过溶剂挥发法制备了三种PLA/天然纤维膜，与纯聚乳酸相比，材料的拉伸强度和拉伸模量有所提高，三种天然纤维增强效果以椰棕纤维最佳，木纤维其次，之后是竹纤维。特别是纤维经过改性之后，增强效果可进一步改善，其中当改性椰棕纤维添加量为2%时，材料的拉伸强度达到最大值，为23.3MPa，较纯PLA提高25%。但是，加入天然纤维后体系的断裂伸长率有一定下降。另外，体系的玻璃化温度和熔融温度无明显提高，但体系熔融焓增加，结晶度有所提高。（2）通过溶液插层方法，制备了蒙脱土/壳聚糖（简称MMT/CS）插层复合物，并对CS相对分子量、CS用量、插层反应温度、插层反应时间等因素对插层效果的影响进行了研究；插层复合物的结构通过XRD, TEM, TGA，FTIR等进行了表征。研究结果表明：随着CS分子量降低，插层复合物的层间距逐渐增大；随着反应温度的上升，插层复合物的层间距呈现先增大后减小的趋势；随着反应时间的延长，插层复合物的层间距先增大后逐渐趋于平衡。在60℃下，相对分子量为3000的CS，插层反应时间为6h时，所得到的MMT/CS插层复合物的层间距最大，从原土的层间距1.44nm增大到1.84nm。（3）PLA/MMT复合材料通过溶剂挥发法制得，材料性能通过万能材料试验机、DMA、XRD、TEM、TGA等进行了表征。结果表明，体系的机械性能有一定提高，拉伸强度提高了将近8MPa，拉伸模量从120MPa提高到了1750MPa。体系的热性能也得到了一定改善，蒙脱土的加入有效提高了体系的玻璃化转变温度，蒙脱土添加量为2%时，体系的玻璃化温度提高最为显著，从59.7°C提高到70.1°C。此外，体系的结晶度也有一定提高。因此，体系的力学性能和热性能均得到改善，达到预期目的。更多还原

【Abstract】 Poly(lactic acid)(PLA) is a biodegradable polymer produced fromrenewable resources, and it has a broad market prospect and is universallyrecognized as the most promising biomedical materials and new-stylepacking materials in the new century. Besides, PLA which is expected tobe substitute of general plastics is environmental and sustainable.However, some factors such as hydrophobic, brittleness, low impactresistance and high cost, especially, the sensitivity to the temperature ofPLA, limit the use of PLA in engineering field. Therefore, themodification of the mechanical properties and thermal properties of PLAbecome the focus of research at present.In this paper, we studied the method to reinforce and toughen PLAby means of melting blend with fillers, which could widen the commonuse of PLA. Meanwhile, it would accelerate the popularization ofbiodegradable materials. In this study, the composites of natural fiber andMMT/PLA were prepared by solution-casting. The composites werecharacterized by DMA, TGA, DSC, SEM, TEM etc. The result indicated:(1) The evaluation of the composite mechanical propertiesdemonstrated that the tensile strength was improved in the presence of natural fiber, and the PLA/2%MCF system had highest modulus.Moreover the modified natural fibers/PLA system had higher strengthwith respect to unmodified ones. However, the elongation at break of thesamples was down after the higher content of natural fibers blended inPLA. Besides, the Tgand Tmof the composites were not improvedsignificantly.(2) MMT/CS composites were prepared by solution-mixingtechnique, and primary studies were carried out on the factors such astime, temperature, the dosage of CS and the mass molar of CS. Thestructure of CS/MMT was analyzed by XRD, TEM, TGA and FTIR. Theresult showed that, as CS molecular weight was reduced, the interlayerspacing of the composites became larger; With increasing reactiontemperature, the interlayer spacing of the composites presented firstincreased, then decreased; With the extension of reaction time, theinterlayer spacing of the composites presented first increased, then tendedgradually balance. when the mass molar of CS was3000, the suitabletemperature and time for intercalation were about60℃and6hrespectively, interlayer space was the largest, the interlayer spacingincreased from1.44nm to1.84nm.(3) PLA/MMT were prepared by solution-casting. The morphologyand properties of PLA/MMT were characterized by DMA, XRD, TEM,TGA. Result showed that the mechanical properties of the composites was improved, the tensile strength improved20MPa, the tensile modulusincreased from120MPa to1750MPa. Besides, the heat resistance of thecomposites was also improved, the addition of the MMT improved the Tgof the composites. When the content of MMT was2%, Tgof thecomposites was70.1°C. Moreover, the degree of crystallinity wasimproved too. In conclusion, the mechanical properties and heatresistance were both improved, the research achieved desired result.更多还原