【摘要】：通過混合兩種或兩種以上的材料制備性能優(yōu)越的復合材料是目前材料領(lǐng)域的重要方法之一。此法可以完善單一材料帶來的缺陷,同時實現(xiàn)材料之間的優(yōu)勢互補,甚至還能賦予材料新的功能。將碳納米材料與聚合物復合,是實現(xiàn)無機材料與有機材料優(yōu)勢互補的有效途徑。眾所周知,聚乳酸(PLA)作為理想的綠色高分子材料之一,其晶型形成主要依賴于熱處理或其成型加工工藝,并且在外場作用下可以實現(xiàn)晶型之間相互轉(zhuǎn)變。PLA的力學性能和降解性能均受其結(jié)晶形態(tài)的影響。因而,研究碳納米材料對PLA高壓結(jié)晶行為的影響,以壓力和碳納米材料協(xié)同調(diào)控其多層次凝聚態(tài)結(jié)構(gòu)及環(huán)境降解性能,就具有特別重要的意義。本文將PLA與不同的碳納米材料[碳納米管(CNT),石墨烯納米片(GNP)和石墨烯(Gr)]進行復合,通過簡單的機械熔融共混法,制備了PLA/CNT、PLA/GNP口PLA/Gr復合材料,并分別對不同復合材料的高壓結(jié)晶和水解降解行為進行了研究。主要的工作和結(jié)論如下：(1)通過透射電子顯微鏡(TEM)觀察了三種碳納米材料在PLA基體中的分散狀況,表明僅CNT在PLA/CNT(95/5,wt/wt)復合材料中出現(xiàn)了小尺寸團聚,而GNP和Gr均可以在PLA基體中均勻分散,且均以折疊片狀形式存在于基體中。(2)根據(jù)熱分析結(jié)果,三種碳納米材料在PLA基體中均為有效的異相成核劑,提高PLA的成核密度并降低了晶體尺寸。但是,對三種碳納米材料而言,高壓下誘導結(jié)晶的能力并不相同,GNP最強,Gr次之,CNT最差。而且最適合三種復合材料高壓結(jié)晶的條件并不相同。PLA/CNT(95/5,wt/wt)和PLA/Gr(99/1,wt/wt)復合材料的最適條件為：在140℃,200 MPa的條件下保溫4 h,結(jié)晶度達到最大(分別為52.54%和51.6%)。而PLA/GNP(99/1,wt/wt)復合材料的最適條件為：在180℃,200 MPa條件下保溫4 h,結(jié)晶度最大則達到55.17%。過高的溫度和壓力并不利于復合材料的高壓結(jié)晶。(3)通過廣角X射線衍射(WAXD)、差示掃描量熱儀(DSC)及掃描電子顯微鏡鏡(SEM)分析復合材料的晶體結(jié)構(gòu),發(fā)現(xiàn)三種碳納米材料的加入均不改變PLA的晶型,PLA在復合材料中主要以α晶體存在。由于高壓和碳納米材料的存在,復合材料在高壓下結(jié)晶得到的晶體尺寸與純聚乳酸相比較小,且存在有更多的缺陷。(4)進行水解降解后發(fā)現(xiàn)：三種復合材料高壓結(jié)晶樣品不同溶液中的水解降解速率均遵循堿性最快,酸性次之,中性最慢的規(guī)律。CNT和GNP的加入均會在不同程度上提高PLA的水解降解速率,Gr的加入則使樣品的水解降解速率變?yōu)榭煽?通過改變制備樣品時的壓力可以調(diào)控樣品的水解降解速率。綜合分析激光共聚焦顯微鏡(LSCM)和質(zhì)量損失曲線的結(jié)果,發(fā)現(xiàn)三種復合材料中PLA在酸性和中性條件下的水解降解均遵循本體腐蝕機理,堿性條件下的水解降解則為表面腐蝕機理。
[Abstract]:It is one of the most important methods in the field of materials to prepare composite materials with superior properties by mixing two or more kinds of materials. This method can perfect the defects brought by a single material, at the same time realize the complementary advantages between the materials, and even endow the material with new functions. It is an effective way to complement the advantages of inorganic materials and organic materials by combining carbon nano-materials with polymers. As we all know, polylactic acid (PLA) is one of the ideal green polymer materials, and its crystal formation mainly depends on the heat treatment or its molding process. The mechanical properties and degradation properties of PLA are affected by its crystalline morphology. Therefore, it is of great significance to study the effect of carbon nanomaterials on the crystallization behavior of PLA at high pressure, and to regulate their multi-layer condensed matter structure and environmental degradation performance by means of pressure and carbon nano-materials. In this paper, PLA was compounded with different carbon nano-materials [carbon nanotube (CNT), graphene (GNP) and graphene (Gr)], and PLA/CNT,PLA/GNP PLA/Gr composites were prepared by simple mechanical melt blending method. The high pressure crystallization and hydrolysis degradation behavior of different composites were studied. The main work and conclusions are as follows: (1) the dispersion of three carbon nano-materials in PLA matrix was observed by transmission electron microscopy (TEM). The results show that only CNT in PLA/CNT (95 / 5). Small size agglomeration occurs in wt/wt) composites, while both GNP and Gr can be uniformly dispersed in PLA matrix and both exist in the form of folded sheets. (2) according to the results of thermal analysis, The three kinds of carbon nanomaterials are effective heterogeneous nucleating agents in PLA matrix, which can increase the nucleation density of PLA and decrease the crystal size. However, for the three carbon nanomaterials, the ability to induce crystallization under high pressure is not the same, GNP is the strongest, Gr is the second, and CNT is the worst. Moreover, the optimum conditions for crystallization of the three composites at high pressure are different. The optimum conditions for PLA/CNT (95 / 5 wt / wt) and PLA/Gr (99.1 / wt) composites are as follows: heat preservation for 4 h at 140 鈩，

本文編號：2294711