本文選題：聚乳酸　切入點(diǎn)：熔體結(jié)構(gòu)　出處：《鄭州大學(xué)》2017年碩士論文

【摘要】：聚乳酸(PLA)作為一種半結(jié)晶高分子材料,具有良好的生物可降解性和生物相容性。PLA制品的力學(xué)性能、耐熱性和降解性能依賴于其成型過程中形成的結(jié)晶形態(tài)結(jié)構(gòu)。由于PLA成核困難、結(jié)晶速率慢,導(dǎo)致通常成型條件下常得到非晶制品,從而限制了其應(yīng)用。提高成核效率可以促進(jìn)PLA結(jié)晶并改善其性能,PLA成核調(diào)控的相關(guān)研究引起了廣泛關(guān)注。為了提高聚乳酸制品的結(jié)晶度,常采用加入成核劑以提高聚乳酸的成核密度。高分子的成核與結(jié)晶行為是影響其結(jié)晶形態(tài)結(jié)構(gòu)的關(guān)鍵因素,其中流動(dòng)與自成核能明顯加快成核并提高成核密度。本文主要研究了流場(chǎng)作用下聚乳酸有序熔體對(duì)結(jié)晶行為的影響,主要研究?jī)?nèi)容和結(jié)果如下:采用原位X射線散射和衍射的方法研究了聚乳酸的熔融和結(jié)晶行為。通過改變部分熔融溫度和部分熔融時(shí)間的方式,制備了具有不同熱歷史的聚乳酸熔體,在隨后的靜態(tài)等溫結(jié)晶實(shí)驗(yàn)中發(fā)現(xiàn):(1)隨著部分熔融溫度的升高,結(jié)晶度逐漸降低;(2)隨著部分熔融時(shí)間的延長(zhǎng),結(jié)晶度略有降低;(3)從有序熔體降溫結(jié)晶過程中,最快結(jié)晶溫度在110℃至120℃之間,在110℃等溫結(jié)晶5 min時(shí),結(jié)晶度達(dá)到5%左右。在120℃等溫結(jié)晶5 min時(shí)結(jié)晶度達(dá)到3%左右。對(duì)含有初始有序結(jié)構(gòu)的熔體施加剪切,在隨后的等溫結(jié)晶過程中發(fā)現(xiàn):(1)與空白熔體相比,有序熔體施加剪切后結(jié)晶度都有明顯提高;(2)與有序熔體靜態(tài)結(jié)晶過程相比,施加剪切后的結(jié)晶度明顯提高;(3)隨著部分熔融溫度的升高,結(jié)晶度逐漸降低;(4)隨著剪切應(yīng)力的增加,樣品取向程度逐漸增大,結(jié)晶進(jìn)程逐漸加快;(5)施加剪切后聚乳酸有序熔體的結(jié)晶速度明顯加快,在110℃和120℃等溫結(jié)晶5 min時(shí)都可以達(dá)到40%以上的結(jié)晶度。
[Abstract]:Polylactic acid (PLA), as a semi-crystalline polymer, has good biodegradability and biocompatibility. The mechanical properties, heat resistance and degradation properties of PLA products depend on the crystalline structure formed during the molding process.Due to the difficulty of nucleation and the slow crystallization rate of PLA, amorphous products are often obtained under normal forming conditions, which limits its application.Increasing nucleation efficiency can promote the crystallization of PLA and improve its performance.In order to improve the crystallinity of polylactic acid products, nucleating agent is often used to increase the nucleation density of polylactic acid.Nucleation and crystallization behavior of polymers are the key factors affecting their crystalline morphology, in which flow and self-forming nuclear energy can obviously accelerate nucleation and increase nucleation density.In this paper, the effect of polylactic acid ordered melt on crystallization behavior under the action of flow field is studied. The main contents and results are as follows: in situ X-ray scattering and diffraction are used to study the melting and crystallization behavior of polylactic acid.Polylactic acid melts with different thermal histories were prepared by changing the partial melting temperature and partial melting time. In the subsequent static isothermal crystallization experiments, it was found that: 1) with the increase of partial melting temperature,The crystallinity decreased gradually with the prolongation of partial melting time, and the crystallinity decreased slightly. During the cooling crystallization process of the ordered melt, the fastest crystallization temperature was between 110 鈩，

本文編號(hào)：1714798