發(fā)布時(shí)間：2018-10-30 15:59

【摘要】：聚乳酸(PLA)是一種有很大潛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、機(jī)械性能良好,在醫(yī)藥領(lǐng)域、包裝材料方面都有很大的應(yīng)用。為了擴(kuò)大PLA的應(yīng)用,經(jīng)常會(huì)用化學(xué)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結(jié)晶與相分離對(duì)于擴(kuò)大聚乳酸應(yīng)用范圍具有重要意義。本文主要進(jìn)行了以下三個(gè)方面的研究:研究了PLLA/PDLA共混體系立構(gòu)復(fù)合中間相的形成以及生長過程,以及立構(gòu)復(fù)合中間相的分子結(jié)構(gòu);制備了以離子液體增塑PLA的共混物,使用介電譜研究了其在加熱退火以及機(jī)械拉伸條件下的相分離過程;不同比例的聚乳酸/離子液體共混體系熱致相分離的調(diào)控及其透氣性能研究。具體結(jié)果如下:(1)揭露了1:1比例的PLLA和PDLA在剛剛高于玻璃化溫度的溫度退火時(shí)會(huì)形成立構(gòu)復(fù)合中間相。它的結(jié)構(gòu)類似于聚乳酸立構(gòu)復(fù)合晶體,是由PLLA和PDLA分子鏈間微弱的相互作用力所致。在這很小的溫度范圍內(nèi),立構(gòu)復(fù)合中間相的形成會(huì)隨著退火溫度的增大而增強(qiáng),生長過程用Avrami方程計(jì)算數(shù)值為3。在80℃以上加熱時(shí)立構(gòu)復(fù)合中間相會(huì)溶解,熔融重結(jié)晶變成同質(zhì)晶體。形成同質(zhì)晶體需要PLLA或PDLA分子鏈從立構(gòu)復(fù)合中間相中分離出來,從而立構(gòu)復(fù)合中間相在一定程度上阻礙了同質(zhì)晶體的形成。(2)使用高電導(dǎo)率的離子液體增塑聚乳酸可以增強(qiáng)其介電常數(shù)。分別通過退火處理和機(jī)械拉伸誘導(dǎo)相分離來進(jìn)一步增強(qiáng)介電常數(shù)�？梢酝ㄟ^介電譜來監(jiān)控離子液體增塑聚乳酸體系的相分離程度。相分離程度隨聚乳酸基體退火結(jié)晶程度的增加而增加,其介電常數(shù)也增加。聚乳酸增塑體系不同機(jī)械拉伸應(yīng)變過程中形成了中間相和晶體。相應(yīng)的,介電常數(shù)和相分離受拉伸應(yīng)變影響。(3)研究了聚乳酸離子液體共混膜的相分離過程及其透氣性能。分別通過30℃退火以及不同溫度熱致相分離法制備聚乳酸/離子液體多孔膜。通過觀察電鏡圖譜發(fā)現(xiàn):30℃退火的樣品在隨著離子液體含量的增加,其結(jié)晶收縮相分離的程度也在增加,水蒸氣透過率也越大,其中60 wt%離子液體含量的膜達(dá)到最佳,水蒸氣透過率在864.1 g/m2*24h;在不同溫度熱致相分離法制備的共混膜中,熱處理的溫度越低,水蒸氣透過率也越大,其中40 wt%離子液體含量在80℃熱致相分離效果達(dá)到最佳,水蒸氣透過率在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，

本文編號(hào)：2300468