聚乳酸共混物结晶相分离行为及其性能
发布时间：2018-10-30 15:59
【摘要】：聚乳酸(PLA)是一种有很大潜力去替代石油基高分子的可生物降解生物基材料。PLA材料的生物相容性、机械性能良好,在医药领域、包装材料方面都有很大的应用。为了扩大PLA的应用,经常会用化学改性、物理改性等共混方法去改善PLA的性能。研究聚乳酸共混物的结晶与相分离对于扩大聚乳酸应用范围具有重要意义。本文主要进行了以下三个方面的研究:研究了PLLA/PDLA共混体系立构复合中间相的形成以及生长过程,以及立构复合中间相的分子结构;制备了以离子液体增塑PLA的共混物,使用介电谱研究了其在加热退火以及机械拉伸条件下的相分离过程;不同比例的聚乳酸/离子液体共混体系热致相分离的调控及其透气性能研究。具体结果如下:(1)揭露了1:1比例的PLLA和PDLA在刚刚高于玻璃化温度的温度退火时会形成立构复合中间相。它的结构类似于聚乳酸立构复合晶体,是由PLLA和PDLA分子链间微弱的相互作用力所致。在这很小的温度范围内,立构复合中间相的形成会随着退火温度的增大而增强,生长过程用Avrami方程计算数值为3。在80℃以上加热时立构复合中间相会溶解,熔融重结晶变成同质晶体。形成同质晶体需要PLLA或PDLA分子链从立构复合中间相中分离出来,从而立构复合中间相在一定程度上阻碍了同质晶体的形成。(2)使用高电导率的离子液体增塑聚乳酸可以增强其介电常数。分别通过退火处理和机械拉伸诱导相分离来进一步增强介电常数。可以通过介电谱来监控离子液体增塑聚乳酸体系的相分离程度。相分离程度随聚乳酸基体退火结晶程度的增加而增加,其介电常数也增加。聚乳酸增塑体系不同机械拉伸应变过程中形成了中间相和晶体。相应的,介电常数和相分离受拉伸应变影响。(3)研究了聚乳酸离子液体共混膜的相分离过程及其透气性能。分别通过30℃退火以及不同温度热致相分离法制备聚乳酸/离子液体多孔膜。通过观察电镜图谱发现:30℃退火的样品在随着离子液体含量的增加,其结晶收缩相分离的程度也在增加,水蒸气透过率也越大,其中60 wt%离子液体含量的膜达到最佳,水蒸气透过率在864.1 g/m2*24h;在不同温度热致相分离法制备的共混膜中,热处理的温度越低,水蒸气透过率也越大,其中40 wt%离子液体含量在80℃热致相分离效果达到最佳,水蒸气透过率在882.2g/m2*24h。
[Abstract]:Polylactic acid (PLA) is a biodegradable material with great potential to replace petroleum-based polymers. PLA has good biocompatibility and good mechanical properties and is widely used in medicine and packaging materials. In order to expand the application of PLA, chemical modification, physical modification and other blending methods are often used to improve the properties of PLA. It is important to study the crystallization and phase separation of poly (lactic acid) blends. In this paper, the following three aspects were studied: the formation and growth process of the orthotropic mesophase and the molecular structure of the orthotropic mesophase in PLLA/PDLA blends were studied. The blends of PLA plasticized with ionic liquids were prepared. The phase separation process of the blends was studied by dielectric spectroscopy under the condition of heating annealing and mechanical drawing. Study on the Thermo-induced Phase Separation and Gas permeability of Polylactic Acid / Ionic liquid blends with different proportion. The results are as follows: (1) it is revealed that at the 1:1 ratio of PLLA and PDLA, the orthotropic mesophase will be formed when the annealing temperature is just above the glass transition temperature. Its structure is similar to that of poly (lactic acid) compound crystal and is caused by the weak interaction between PLLA and PDLA molecular chains. In this small temperature range, the formation of the composite mesophase increases with the increase of annealing temperature, and the growth process is calculated by Avrami equation to be 3. When heated above 80 鈩，
本文编号：2300468
[Abstract]:Polylactic acid (PLA) is a biodegradable material with great potential to replace petroleum-based polymers. PLA has good biocompatibility and good mechanical properties and is widely used in medicine and packaging materials. In order to expand the application of PLA, chemical modification, physical modification and other blending methods are often used to improve the properties of PLA. It is important to study the crystallization and phase separation of poly (lactic acid) blends. In this paper, the following three aspects were studied: the formation and growth process of the orthotropic mesophase and the molecular structure of the orthotropic mesophase in PLLA/PDLA blends were studied. The blends of PLA plasticized with ionic liquids were prepared. The phase separation process of the blends was studied by dielectric spectroscopy under the condition of heating annealing and mechanical drawing. Study on the Thermo-induced Phase Separation and Gas permeability of Polylactic Acid / Ionic liquid blends with different proportion. The results are as follows: (1) it is revealed that at the 1:1 ratio of PLLA and PDLA, the orthotropic mesophase will be formed when the annealing temperature is just above the glass transition temperature. Its structure is similar to that of poly (lactic acid) compound crystal and is caused by the weak interaction between PLLA and PDLA molecular chains. In this small temperature range, the formation of the composite mesophase increases with the increase of annealing temperature, and the growth process is calculated by Avrami equation to be 3. When heated above 80 鈩，
本文编号：2300468
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