Effect of coagulation temperature on structures and properties of poly(p-phenylene benzobisoxazole) (DHPBO) fibers during dry-jet wet-spinning process

The effect of coagulation temperature on the morphology, microstructures and mechanical properties of dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) fibers was investigated during dry-jet wet-spinning process, in which the coagulation bath concentration and drawn ratio were kept as 10 wt% of PPA in water and 1.7, respectively. The structures and mechanical properties of the as-spun DHPBO fibers were characterized by FTIR, XRD, SEM, and single fiber tensile testing. The results indicated that in PPA/H2O coagulation system, when the coagulation temperature was 25°C, highly crystallized DHPBO as-spun fibers possessing fine crystallites, circular and smooth morphology, and excellent mechanical properties could be achieved.

主链含羟基的芳杂环液晶共聚物聚对苯撑苯并二噁唑的合成及性能研究

通过在聚合过程中添加少量2,5-二羟基对苯二甲酸(DHTA)部分替代对苯二甲酸(TPA)与4,6-二氨基间苯二酚(DAR)盐酸盐进行共聚,合成了一系列大分子链上含有羟基基团的DHPBO共聚物,并制得其初生纤维.利用FTIR、接触角等分析手段对其化学结构和纤维表面性能进行了表征,通过单丝拔出实验和SEM考察了DHPBO纤维与环氧树脂基体的界面剪切强度,并采用轴向压缩弯曲实验和紫外光加速老化实验评价了羟基基团的引入对提高纤维压缩性能和抗紫外性能的影响.结果表明,羟基基团的引入使得DHPBO纤维的表面亲水性、与环氧树脂的界面剪切强度以及纤维的压缩性能和抗紫外性能都有了显著提高.

羟基基团对PBO纤维表面性能及界面粘结性能的影响

以2,5-二羟基对苯二甲酸(DHTA)为改性单体,采用化学共聚改性的方法,合成了大分子链上含有羟基基团的聚对苯撑苯并二噁唑(PBO)与DHTA的共聚物(DHPBO),并通过液晶纺丝技术得到了DHPBO纤维。利用FTIR、接触角等分析手段对其化学结构和纤维表面性能进行了表征,并通过微脱粘实验和SEM评价了DHPBO纤维与环氧树脂基体的界面剪切强度。结果表明:50 mol%DHTA的加入使水在PBO纤维表面的接触角由71.4°减小到50.7°,乙醇在PBO纤维表面的接触角由37.2°减小到27.4°;当DHTA含量为20 mol%时,DHP-BO纤维的表面自由能增加到43.96 mJ/m2,比PBO纤维提高了23.83%。当DHTA含量为10 mol%时,DHPBO纤维与环氧树脂的界面剪切强度为18.87 MPa,比PBO纤维与环氧树脂的界面剪切强度提高了92.55%。