热塑性聚酰亚胺及其改性材料的热性能研究

《材料物理》课程论文学生姓名：梁东学号：20140530学院：材料科学与工程学院专业年级：2014级材料化学2班题目：热塑性聚酰亚胺及其改性材料的热性能研究指导教师：梁金老师评阅教师：梁金老师2016年6月摘要聚酰亚胺（PI）是一种高性能聚合物材料，具有优异的机械性能、电性能、耐辐射性能和耐热性能，广泛应用于航空航天、微电子和通讯等高技术领域，成为很有发展前景的材料之一。

但多数 PI 具有不溶不熔的特性，加工成型十分困难，一定程度上限制了其应用范围，因此热塑性聚酰亚胺（TPI）成为发展方向之一。

TPI 不仅具有优异的综合性能，而且更易于加工，生产效率更高，在经济效益和环保方面都优于传统的热固性聚酰亚胺，成为人们开发研制的热点。

TPI 可通过添加纤维提高力学性能，添加润滑剂提高耐磨性能，亦可与其它聚合物共混，使改性材料具有更优异的性能，应用于高科技领域。

目前，对 PI 及其改性材料性能的研究，大多数是关于力学性能和摩擦磨损性能，很少具体研究其热性能。

而聚酰亚胺的热性能，如玻璃化转变温度 Tg、热膨胀系数α是其应用于工业各领域重要的评价指标。

针对以上背景，本文首先测定了一种自主研发的 TPI 的玻璃化转变温度并通过改变分子量大小考察玻璃化转变温度与分子量的关系，及热处理温度和热处理时间对玻璃化转变温度的影响。

结果表明：玻璃化转变温度随数均分子量的增大而增加，采用 Kanig-Ueberreiter 方程关联玻璃化转变温度与数均分子量,其线性拟合度高；由于聚酰亚胺的结构特点——存在自由端基，在高温可发生固相热环化反应，相应其分子量随处理温度的升高和处理时间的延长而增大，表现为聚合物的玻璃化转变温度有所升高。

为了进一步提高 TPI 的性能，扩大其应用范围，使其能在更加苛刻的环境下使用，TPI 的改性研究主要包括纤维增强的 TPI 树脂基复合材料及聚合物共混改性 TPI。

但由于高分子材料的热膨胀系数比纤维、陶瓷等无机材料要大得多，两者复合后，随温度的变化，热应力不仅使高分子和基材剥离，还会产生龟裂和翘曲，模压塑料则产生裂纹等。

另外高科技的发展，要求器械内部的空间更小，对材料的热稳定和热膨胀性能提出了更高的要求。

因此，本文在上一步工作的基础上，选出一种分子量的 TPI 树脂，测定其注塑件的热膨胀系数及其各向异性和尺寸稳定性；并考察了所添加的填料种类对热膨胀系数的影响。

结果表明：TPI 存在着各向异性，且流向面的热膨胀系数低。

在正常的使用范围内，试样经历一个升降温循环后尺寸基本没发生变化。

消除热历史后，材料的热膨胀系数降低；类似地，热处理也能使热膨胀系数减小。

在主链相同的 TPI 树脂中，加入玻纤、碳纤等高强度、高热稳定性的填料有助于降低 TPI 的热膨胀系数。

对于共混改性的 TPI，主要用熔体流动速率仪研究了 TPI/聚醚醚酮（PEEK）共混物的流变性能，用差示扫描量热仪考察了共混物的相容性和热性能，用广角X 射线衍射仪研究了共混物的形态和结晶性能。

结果表明：共混物的熔体流动指数随 PEEK 含量的降低和熔体温度的升高而增加；TPI/PEEK 共混物为不相容体系；随 TPI 含量的减小，共混体系中 PEEK 的结晶温度和熔点分别升高，而结晶度降低，X 射线衍射的结晶峰越来越明显，峰面积也随之增大。

为了与 PEEK/TPI 共混物进行比较，还考察了 PEEK 与 PEI 共混物的相容性和结晶性能等。

结果表明：PEEK/PEI 共混物完全相容，所有共混物均呈现一个玻璃化转变温度，且与组分的关系符合 Porch 方程；这是由于 PEEK 和 PEI 间的电荷转移相互作用占主导地位。

随 PEI 含量的增加，共混体系的熔点、结晶度、整体结晶速率和结晶能力均降低；而 PEEK 的结晶度呈现先增加后减小的趋势，当 PEI 质量分数为 50%时，达到最大。

关键词热塑性聚酰亚胺玻璃化转变温度热膨胀系数改性共混ABSTRACTPolyimides is an important high-performance polymers used in aircraft, microelectronics, communication fields and so on for their marked thermal-stability, excellent mechanical, electrical and radiation–resistance properties. However, manyof these polyimides are insoluable and infusible, leading them impossible to process by the conventional methods, which has confined the widespread use of the polyimides. So the thermoplastic polyimides (TPI) are becoming one of the development directions. TPI preparation research has become popular project in owing to they are not only provided outstanding comprehensive properties, but also can be easily processed, with high production efficiency, and are better than thermosetting polyimides at economic effectiveness and environmental friendly. In order to improve TPI’s mechanical or tribological properties, the fibers and or lubricants are filled into the resin; another way is to make TPI blend with other polymers especially for application in high-tech fileds. At present, many research works on TPI composite materials are focused on the mechanical and tribological properties, rarely on the thermal properities. But the thermal properities of TPI, suchas glass transition temperature (Tg) and coefficient of thermal expansion (CTE), are considered as the important indexes as TPI is applied in industries.Based on above background, the Tg for TPI were measured in this paper, and the effects on Tg, such as molecular weight, heat treated temperature and heat treated time were also investigated. The results showed that Tg was increased with increase of the molecular weight, meanwhile the Kanig-Ueberreiter equation provided a good fit to Tg and number-average molecule weight. Due to the TPI structure feature which contained the free end group, solid therm-cyclization could be carried out at high temperature. Accordingly, the molecular weight and Tg are also increased with increase of the heat treated temperature and time.In order to extend the TPI application area especially in the rigoroussurroundings, the TPI had been modified by filling fiber and or mixing with other polymers. Because the CTE for polymer is larger than those of fiber and ceramic, the phase separation and thermal stress might be take place for their composite, as results, the crack and or distortion will ocurr with the change of temperature. Moreover, the thermal-stability and thermal expansion properties should be needed in the high-tech areas.The CTE of TPI resin with appropriate molecular weight was measured, and its anisotropy and dimensional stability were also determined by TMA. The effect of fillings on the CTE was further investigated in this work. The results showed that TPI existed anisotropy, and the CTE was the smallest at flow direction. The dimension almost did not take change in periods of temperature loop under its working temperature. As relieving of the heat history via heat treating, the CTE would be decreased. The CTE of composite could be decreased if the fillings such as glass fiber and carbon fiber with high strength and themal stability were added.The processability, compatibility, thermal properities, morphologies and crystallization of the TPI/PEEK blends were investigated by means of melt flow indexer, differential scanning calorimeter（DSC）and wide angle X-ray scattering （WAXD）. The results indicated that the melt flow index of the blends was increased with decrease of PEEK content and or increase of melt temperature. The blends for TPI and PEEK were considered to be imcompatible because there appeared two glass temperatures which are corresponding to their pure polymer. With decrease of the TPI content, the crystallization temperature and the melting point of the blends were increased, the crystallinity was reduced. Moreover, the high and area of crystallization peak were increased measured by XRD.The miscibility and crystallization behaviors of the PEEK/PEI blends were also investigated compared with the blends of PEEK/TPI. The results showed that the blends of PEEK/PEI were miscible completely because they exhibited a single Tg which could be described by Porch equation. That is because there exists the charge transfer interaction between PEEK and PEI. The melting point, crystallinity, bulk crystallization rate and crystallization capability for the PEEK/PEI blends were decreased with increase of PEI content, and the crystallinity of PEEK reached maximum at the 50% content of PEI.KEYWORDS Thermoplastic polyimide(TPI)；Glass transition temperature(Tg)；Coefficient of thermal expansion(CTE)；Modify; blend.目录摘要..........................................................................3-5 ABSTRACT....................................................................5-11第一章文献综述...........................................................11-35 1.1 聚酰亚胺简介..........................................................11-17 1.1.1 聚酰亚胺的发展.....................................................11-13 1.1.2 聚酰亚胺的工业现状.................................................13-16 1.1.3 聚酰亚胺的性能.....................................................16-17 1.2 热固性聚酰亚胺与热塑性聚酰亚胺.....................................17-21 1.2.1 热固性聚酰亚胺.....................................................18-19 1.2.2 热塑性聚酰亚胺.....................................................19-21 1.3 聚酰亚胺的复合改性...................................................21-27 1.3.1 PI/无机物复合改性...................................................21-24 1.3.2 PI/聚合物复合改性...................................................24-27 1.4 聚酰亚胺热性能研究进展...............................................27-30 1.4.1 耐热性...............................................................27-28 1.4.2 热膨胀系数..........................................................28-30 1.5 本文研究目标和内容...................................................30-31参考文献...................................................................31-35第二章热塑性聚酰亚胺热转变行为研究....................................35-46 2.1 实验部分...............................................................35-36 2.1.1 试样制备 (35)2.1.2 测试仪器及条件.....................................................35-36 2.2 结果与讨论............................................................36-43 2.2.1 分子量的测定........................................................36-372.2.2 玻璃化转变温度与分子量的关系.....................................37-39 2.2.3 热处理对T_g 的影响.................................................39-43 2.3 小结...................................................................43-44参考文献...................................................................44-46第一章文献综述1.1 聚酰亚胺简介聚酰亚胺（PI）是在 50 年代中期为了满足当时航空、航天技术对于耐高温、高强度、高模量、高介电性能、耐辐射的高分子材料的需要而在美国和苏联率先发展起来的。