聚氧化乙烯对聚乳酸结晶结构的影响

发布时间：2018-04-15 08:08

  本文选题：聚乳酸 + 聚氧化乙烯　； 参考：《郑州大学》2017年硕士论文

【摘要】：聚乳酸(PLA)是一种来源于可再生资源的重要的可生物降解结晶性聚合物。但是PLA的脆性大,限制了它的应用范围。将PLA和低玻璃化转变温度(Tg)的聚合物共混是改善其韧性的重要手段。聚氧化乙烯(PEO)是一种重要的低Tg聚合物,同时还具有毒性低、生物相容性好的优点。因此,PLA/PEO共混体系已得到越来越多的关注。本论文重点研究了PEO组分的引入对PLA多晶型结构的影响,主要结果如下:(1)熔融结晶条件下PEO对PLA多晶型结构影响的研究。通过熔融共混法制备了组分含量分别为(100/0)、(90/10)和(80/20)的PLA/PEO共混物,利用广角X射线衍射仪(WAXD)研究了等温熔融结晶条件下PEO对PLA晶体结构的影响,结果表明:纯PLA在Tc≤110 oC和Tc110 oC结晶分别形成α′晶α晶。而在PLA/PEO共混物中,WAXD衍射曲线上(110/200)晶面和(203)晶面的衍射峰不随等温结晶温度Tc的变化而发生偏移,没有观察到明显的α′晶,表明PEO的存在促进了PLA中α晶的形成。接下来,借助差示扫描量热仪(DSC)研究了PEO对PLA结晶行为的影响,并利用Avrami模型对其结晶动力学进行了分析,结果表明:PEO的引入并没有明显改变PLA的Avrami指数,表明PEO没有影响PLA的结晶机理;另一方面,PEO的引入明显提高了PLA的结晶速率,这可归因于共混物Tg和平衡熔点的降低,从而促进了PLA分子链的运动。(2)冷结晶条件下PEO对PLA多晶型结构影响的研究。通过熔融共混法制备了组分含量分别为(100/0)、(99/1)、(98/2)、(95/5)、(90/10)和(80/20)的PLA/PEO共混物,利用WAXD研究了PEO对PLA等温冷结晶晶体结构的影响。结果表明:纯PLA在Tc110 oC冷结晶时得到的晶体是α′晶,当Tc≥110 oC形成α晶;随着共混物中PEO含量的增大,PLA形成α′晶和α晶的临界温度没有明显变化,但是α′晶和α晶的2θ角的差值逐渐缩小,当PEO含量增大到10%及以上时,已观察不到明显的α′晶的存在。另外,还利用WAXD原位研究了在Tc=90 oC冷结晶PLA及其与PEO的共混物在升温过程中结晶结构的演化,结果表明,纯PLA在升温过程中有明显的α′晶到α晶的晶型转变,这种转变也存在于(99/1)、(98/2)、(95/5)PLA/PEO共混体系中。
[Abstract]:Polylactic acid (PLA) is a kind of come from renewable resources important biodegradable crystalline polymer. But PLA brittleness limits its scope of application. The PLA and low glass transition temperature (Tg) of the polymer blend is an important means to improve its toughness. Poly ethylene oxide (PEO) is a low Tg polymer is important, but also has low toxicity, good biocompatibility and good. Therefore, PLA/PEO blends has gained more and more attention. This paper focuses on the impact of the introduction of the PEO component of PLA polycrystalline type structure, the main results are as follows: (1) study on the effect of melt crystallization under the condition of PEO on the PLA crystal structure. Prepared by melt blending components respectively (100/0), (90/10) and (80/20) PLA/PEO blends, using the wide angle X - ray diffraction (WAXD) studies the effects of isothermal Melt Crystallization Conditions on the crystal structure of PLA PEO, The results show that the pure PLA crystal form alpha 'alpha crystal respectively in Tc and Tc110 less than 110 oC. The crystallization of oC in PLA/PEO blends, WAXD diffraction curve (110/200) and (203) crystal plane diffraction peak did not change with the isothermal crystallization temperature of Tc and shift, not observed in alpha' crystal obviously, indicated that PEO promoted the formation of a crystal in PLA. Then, by means of differential scanning calorimetry (DSC) to study the effects of PEO on the crystallization behavior of PLA, and the crystallization kinetics was analyzed using the Avrami model results show that the introduction of PEO and PLA did not significantly alter the Avrami index PEO, that does not affect the crystallization mechanism of PLA; on the other hand, the introduction of PEO can significantly improve the crystallization rate of PLA decreased, which could be attributed to the blend of Tg and the equilibrium melting point, thus promoting the movement of PLA molecular chain. (2) study on the influence of cold crystallization conditions of PEO polycrystalline PLA type structure. 閫氳繃鐔旇瀺鍏辨贩娉曞埗澶囦簡缁勫垎鍚�閲忓垎鍒�涓，

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