本文選題：PLLA + 球晶形態(tài)��； 參考：《鄭州大學》2015年碩士論文

【摘要】：左旋聚乳酸(PLLA)作為一種綠色可再生且可生物降解的高分子材料,近年來受到了廣泛的關注和研究。然而由于結晶速率慢,結晶度低以及韌性差等限制了PLLA在很多領域的應用,如何解決這些問題一直是人們關注的焦點。材料性能都是由其內部結構決定的,因此本工作從材料的微觀結構出發(fā),研究PLLA晶體的形成以及不同尺度力學性能與結構的關系。一方面可以深刻了解體系內不同晶體的形成機理；另一方面研究微觀尺度材料結構與性能的對應關系,從而用于指導PLLA的生產加工和實現材料的高性能化。本文研究了不同條件形成的PLLA球晶形貌以及對應晶區(qū)和非晶區(qū)的微觀力學性能；并且研究了聚乳酸立構復合晶體形成條件及其復合改性對材料性能的影響,具體研究內容如下：(1)利用偏光顯微鏡觀察了PLLA球晶生長過程,并且發(fā)現PLLA球晶在冰水中淬冷后形成環(huán)帶同心圓或者六邊形裂紋,且裂紋的形狀與球晶尺寸相關,當球晶較小時,裂紋不明顯,隨著尺寸增加,開始形成規(guī)則的正六邊形,繼續(xù)增加尺寸,其形貌呈現等間距同心環(huán)裂紋；掃描電鏡(SEM)結果表明：球晶區(qū)斷裂處存在明顯的縫隙,而在球晶生長前端裂紋不明顯；并且通過納米壓痕儀測試了球晶內部不同位置以及無定形區(qū)的微觀力學性能,發(fā)現晶體的硬度和模量均高于非晶區(qū),且球晶存在生長前端,其微觀性能參數均處于晶區(qū)和非晶區(qū)之間。(2)利用X射線衍射儀(XRD)、差示掃描量熱儀(DSC)、動態(tài)力學分析儀(DMA)及拉伸測試技術研究了立構復合聚乳酸(SC)晶體的形成條件以及對材料性能的影響。通過對比發(fā)現溶液成型更加有利于SC晶體的形成,而熱壓成型則會破壞已經形成的SC晶體。非晶PLLA/PDLA復合體系在熔融升溫發(fā)生冷結晶,其不僅包括聚乳酸均聚物(HC)晶體,同時也有SC晶體的存在。熱處理能夠提高PLLA/PDLA復合體系的結晶度但對SC晶體影響不大。并且發(fā)現在90℃退火材料的斷裂伸長率最高,這可能是由于在此溫度退火過程中發(fā)生了相轉變。(3)采用溶液澆鑄法制備PLLA/BC-g-MAH復合材料,并通過傅里葉紅外光譜儀(FTIR)、DSC、熱重分析儀(TGA)及拉伸測試技術研究PLLA/BC-g-MAH復合材料的結晶行為及其力學性能。結果表明：用馬來酸酐(MAH)對BC進行接枝可以改善BC-g-MAH與PLLA之間的界面相容性；PLLA/BC-g-MAH復合材料結晶及力學性能隨著BC-g-MAH的增加而顯著提高。同時,由于結晶結構更為完善使得復合材料熱穩(wěn)定性能也有較大的提高。
[Abstract]:As a green and biodegradable polymer, PLLA has been widely studied in recent years.However, the slow crystallization rate, low crystallinity and poor toughness limit the application of PLLA in many fields. How to solve these problems has been the focus of attention.The properties of the materials are determined by their internal structures. Therefore, the formation of PLLA crystals and the relationship between mechanical properties and structures at different scales are studied from the microstructure of the materials.On the one hand, the formation mechanism of different crystals in the system can be deeply understood; on the other hand, the relationship between the microstructure and the properties of the microscale materials can be studied, which can be used to guide the production and processing of PLLA and to realize the high performance of the materials.In this paper, the morphologies of PLLA spherulites formed under different conditions and the micromechanical properties of the corresponding crystalline and amorphous regions are studied, and the effects of the formation conditions and their modification on the properties of the composites are also studied.The specific research contents are as follows: (1) the growth process of PLLA spherulites was observed by using a polarizing microscope, and it was found that the PLLA spherulites formed concentric circles or hexagonal cracks after quenching in ice water, and the shape of the cracks was related to the size of the spherulites, when the spherulites were small,The crack was not obvious, and with the increase of size, regular hexagon began to form, and the size continued to increase, and the morphology of the crack appeared concentric ring crack with equal spacing, and the SEM results showed that there were obvious cracks in the fracture of spherulite region.The micromechanical properties of the spherulites at different positions and amorphous regions were tested by nano-indentation instrument. It was found that the hardness and modulus of the crystals were higher than that of the amorphous regions, and the spherulites had the growth front end.The microcosmic property parameters are between the crystal region and the amorphous region.) using X-ray diffractometer, differential scanning calorimeter (DSCO), dynamic mechanics analyzer (DMA) and tensile test technique, the formation conditions of the orthotropic composite polylactic acid (SCL) crystal have been studied by means of X-ray diffractometer, differential scanning calorimeter (DSC), dynamic mechanics analyzer (DMA) and tensile test technique.And its effect on the properties of materials.It is found that the solution forming is more favorable to the formation of SC crystal, while the hot pressing will destroy the formed SC crystal.Cold crystallization occurs in amorphous PLLA/PDLA composite system at melting temperature, which includes not only polylactic acid homopolymer PLLA/PDLA] crystal, but also SC crystal.Heat treatment can improve the crystallinity of PLLA/PDLA composite system, but has little effect on SC crystal.It is also found that the highest elongation at break of the annealed material at 90 鈩，

本文編號：1767758