Thermoplastic Sizing of Carbon Fibres in High Temperature Polyimide Composites

Thermoplastic sizing of various carbon fibres has been evaluated as a means of controlling the microcracking resistance, transflexural strength (TFS), and thermo-oxidative stability (TOS) of PMR-15 matrix composites. Four different fibre/thermoplastic size combinations were selected for this study, based on their higher TOS than appropriate controls. Data are presented for the transverse microcrack (TVM) density/inch, and the subsequent delamination of [0,90]_4s laminates induced by thermal cycling (-196 to 350°C for 20 cycles). Results for composite TFS, conditioned TFS (after heating in air at 350°C), and TOS (350°C and 316°C) are also reported. One fibre/thermoplastic size combination gave both good microcracking resistance, and significantly improved TOS, in composite when compared with current commercially-available material.     

Self adhesion of short Kevlar fibre-thermoplastic polyurethane composite

The self adhesion behaviour of thermoplastic polyurethane (TPU) in itself and its composite with short Kevlar fibre with respect to contact time, temperature, pressure, and fibre loading has been studied. The adhesion strength showed two linear increments of different slopes with respect to the square root of time: with temperature and pressure of contact, the adhesion strength was improved. The maximum strength was obtained with 20 phr of short fibre in only one of the mating substrates in the peel test sample. The duration for wetting and diffusion was shifted to longer time intervals with fibres loaded in both the substrates.     

Flexible Backbone Aromatic Polyimide Adhesives

Continuing research at Langley Research Center on the synthesis and development of new inexpensive flexible aromatic polyimides as adhesives has resulted in a material identified as LARC-F-SO₂ with similarities to polyimidesulfone (PISO₂) and other flexible backbone polyimides recently reported by Progar and St. Clair. Also prepared and evaluated was an endcapped version of PISO₂. These two polymers were compared with LARC-TPI and LARC-STPI, polyimides researched in our laboratory and reported in the literature.

The adhesive evaluation, primarily based on lap shear strength (LSS) tests, involved preparing adhesive tapes, conducting bonding studies and exposing lap shear specimens to 204°C air for up to 1000 hrs and to a 72-hour water boil. LSS tests at RT, 177°C and 204°C were performed before (controls) and after these exposures. The type of adhesive failure as well as the Tg was determined for the fractured specimens.

The results indicate that LARC-TPI provides the highest LSSs, 33 MPa at RT, 30 MPa at 177°C, and 26 MPa at 204°C. LARC-F-SO₂, LARC-TPI and LARC-STPI all retain their strengths after thermal exposure for 1000 hrs and PISO₂ retains greater than 80% of its control strengths.

Most of the four adhesive systems showed reduced strengths for all test temperatures although they still retained a high percentage of their original strength (<60%) except for one case.

The predominant failure mode was cohesive with no significant change in the Tgs.

Although the LARC-F-SO₂ could not be prepared in diglyme alone as the solvent, the properties of the resulting adhesive were notable. The darkening of the adhesive during bonding was typical of systems which utilize amide solvents.     

热塑性弹性体改性B炸药的性能研究

添加2%热塑性弹性体401和501对B炸药改性,得到改性后炸药MB-1和MB-2,测试了二者的力学性能和落锤撞击感度,分别用经验法和VLWR程序计算了二者的爆轰性能。结果表明,MB-1和MB-2的弹性和韧性均好于B炸药;在低速(100-1500s-1)冲击下,MB-2的韧性比MB-1好。大药片落锤撞击感度试验中,MB-1和MB-2的爆炸反应阈值高度分别为3.5-4m和6-6.5m,MB-1的撞击感度比MB-2高。与B炸药相比,MB-1和MB-2的爆速分别降低了0.104mm·μs-1和0.099mm·μs-1,爆压分别降低了1.3GPa和1.2GPa。     

一种热塑态真空振动装药工艺

为提高弹药产品质量及生产过程的本质安全度,改善现有热塑态装药生产条件,针对常规热塑态装药方法存在的缺陷,提出一种将真空振动装药法引入热塑态装药工艺设备的设计方案。综合应用自动控制技术、大型真空室振动装药技术,实现了对弹药产品热塑态装药过程的自动控制,建立了热塑态装药生产线,并在某产品试制中得到成功应用。实践证明:该生产线提高了弹药装药质量和本质安全度,具有较高的经济效益和社会效益。     

PNIMMO基热塑性弹性体的合成及表征

以聚3-硝酸酯甲基-3-甲基氧杂环丁烷(PNIMMO)为软段,2,4-甲苯二异氰酸酯和1,4-丁二醇为硬段(含量为30%~50%),1,2-二氯乙烷为溶剂,采用溶液聚合两步法合成了含硝酸酯基热塑性弹性体(NTPE),确定了异氰酸酯指数为1.02,硬段含量为40%~45%时,聚合物的力学性能较优。采用红外光谱和核磁共振对NTPE的结构进行了表征,结果表明NTPE具有典型的硝酸酯聚醚聚氨酯特征。用差示扫描量热法和热重-微商热重法研究了NTPE的热性能,其玻璃化转变温度为-11.71℃,分解峰温为220.4℃,热失重范围为175~523.63℃,共失重84.44%,热稳定性较好。     

热塑性聚酯工程塑料的进展

综述了世界上几种热塑性聚酯的生产发展及应用进展，指出聚酯工业的4个主要趋势；生产能力逐渐集中，亚洲生产能力增大；欧美撤出聚酯纤维领域和非纤聚酯比例上升，在应用方面，热塑性聚酯多用于制造片（带）材，中空包装容器，电子、家用电器、汽车、精密仪器部件、薄膜及纤维等领域。     

热固性树脂的化学流变性

本文讨论了热固性树脂固化时化学流变性问题,并通过两种途径模拟了热固性树脂的化学粘度.     

AZDEL制品成形技术

AZDEL片材是两层玻璃纤维针刺毡和三层聚丙烯经钢带式层压机压制而成的热塑性玻璃纤维增强片状模塑料.本文介绍了AZDEL制品的成形概要、成形设备以及成形要领.     

动态硫化热塑性弹性体的制备与应用

阐述了动态硫化共混型热塑性弹性体的发展历史和主要的分类，概述了共混型热塑性弹性体的微观形态结构及其形成机理，总结了共混体系的配方和工艺条件对共混物性能和结构的影响，分析了几种典型动态硫化热塑性弹性体的性能特点和应用领域。