Effect of the adding of rod-like attapulgite upon the properties of polyimides produced by random copolycondensation

Abstract

A series of polyimides (PIs) and polyimide/attapulgite (AT) composite films was successfully prepared by random copolycondensation. The polyimides were synthesized based on 4,4′-diaminodiphenyl ether, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), and 4,4′-oxydiphthalic anhydride (ODPA). By adjusting the ratio of BPADA and ODPA, three different types of anhydride group-terminated PIs were obtained. AT was functionalized by chemical modification with γ-aminopropyltriethoxysilane and then chemical bonded with PI via reaction between amino group and anhydride group, resulting in stable PI/AT composites. The structure and properties of PIs and PI/AT composites were characterized by FTIR, XRD, TG, SEM, DSC, DMA, mechanical measure, and so on. Comparison was given between PIs and PI/AT composites. Results showed that all PIs had good thermal stability and mechanical properties with glass translation temperature (T g) over 210 °C, 5 % weight loss temperature (T d,5%) over 494 °C and tension strength of 84–89.9 MPa, breaking elongation around 7 %. More stable, flexible, and much stronger films were obtained after adding 5 wt% AT, which showed 535–548.5 °C, 85.8–118.9 MPa, and 10.3–24.7 % in T d,5%, tension strength, and breaking elongation, respectively. Much interestingly, we found that AT had the greatest effect on PI-2, the yielding of which occurred during mechanical measure, and PI/AT-2 composite displayed excellent comprehensive properties.