一维及二维碳纳米材料对聚乳酸高压结晶及其水解降解行为影响的研究
发布时间：2018-10-25 20:09
【摘要】：通过混合两种或两种以上的材料制备性能优越的复合材料是目前材料领域的重要方法之一。此法可以完善单一材料带来的缺陷,同时实现材料之间的优势互补,甚至还能赋予材料新的功能。将碳纳米材料与聚合物复合,是实现无机材料与有机材料优势互补的有效途径。众所周知,聚乳酸(PLA)作为理想的绿色高分子材料之一,其晶型形成主要依赖于热处理或其成型加工工艺,并且在外场作用下可以实现晶型之间相互转变。PLA的力学性能和降解性能均受其结晶形态的影响。因而,研究碳纳米材料对PLA高压结晶行为的影响,以压力和碳纳米材料协同调控其多层次凝聚态结构及环境降解性能,就具有特别重要的意义。本文将PLA与不同的碳纳米材料[碳纳米管(CNT),石墨烯纳米片(GNP)和石墨烯(Gr)]进行复合,通过简单的机械熔融共混法,制备了PLA/CNT、PLA/GNP口PLA/Gr复合材料,并分别对不同复合材料的高压结晶和水解降解行为进行了研究。主要的工作和结论如下：(1)通过透射电子显微镜(TEM)观察了三种碳纳米材料在PLA基体中的分散状况,表明仅CNT在PLA/CNT(95/5,wt/wt)复合材料中出现了小尺寸团聚,而GNP和Gr均可以在PLA基体中均匀分散,且均以折叠片状形式存在于基体中。(2)根据热分析结果,三种碳纳米材料在PLA基体中均为有效的异相成核剂,提高PLA的成核密度并降低了晶体尺寸。但是,对三种碳纳米材料而言,高压下诱导结晶的能力并不相同,GNP最强,Gr次之,CNT最差。而且最适合三种复合材料高压结晶的条件并不相同。PLA/CNT(95/5,wt/wt)和PLA/Gr(99/1,wt/wt)复合材料的最适条件为：在140℃,200 MPa的条件下保温4 h,结晶度达到最大(分别为52.54%和51.6%)。而PLA/GNP(99/1,wt/wt)复合材料的最适条件为：在180℃,200 MPa条件下保温4 h,结晶度最大则达到55.17%。过高的温度和压力并不利于复合材料的高压结晶。(3)通过广角X射线衍射(WAXD)、差示扫描量热仪(DSC)及扫描电子显微镜镜(SEM)分析复合材料的晶体结构,发现三种碳纳米材料的加入均不改变PLA的晶型,PLA在复合材料中主要以α晶体存在。由于高压和碳纳米材料的存在,复合材料在高压下结晶得到的晶体尺寸与纯聚乳酸相比较小,且存在有更多的缺陷。(4)进行水解降解后发现：三种复合材料高压结晶样品不同溶液中的水解降解速率均遵循碱性最快,酸性次之,中性最慢的规律。CNT和GNP的加入均会在不同程度上提高PLA的水解降解速率,Gr的加入则使样品的水解降解速率变为可控,通过改变制备样品时的压力可以调控样品的水解降解速率。综合分析激光共聚焦显微镜(LSCM)和质量损失曲线的结果,发现三种复合材料中PLA在酸性和中性条件下的水解降解均遵循本体腐蚀机理,碱性条件下的水解降解则为表面腐蚀机理。
[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，
本文编号：2294711
[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，
本文编号：2294711
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