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A series of inherently heat-sealable copolyimides (CPIs) with high glass transition temperatures were synthesized from 2,3,3',4'-oxydiphthalic anhydride (aODPA) and bicomponent diamines, 4,4'-oxydianiline (ODA) and para-phenylenediamine (PDA). The PI chain rigidity was manipulated by the regulation of the diamine ratio, and its effects on the heat sealability and thermal resistance of the derived CPI films were investigated in detail. The results show that these films are in possession of both good heat sealability and thermal resistance due to the synergetic effect of the asymmetry of aODPA and the rigidity of PDA. It is also found that there exists one critical PDA content that distinguishes the heat-sealing behaviors of the CPI films, and the relevant mechanism was established. Especially for CPI-5, the heat-sealing strength is up to 350 N m–1 simultaneously with a relatively high Tg of 310°C. [ABSTRACT FROM AUTHOR]

ABSTRACT Two novel aromatic tetraamines containing bulky lateral phenyl unit and multiple trifluoromethyl groups, 1,1-bis[4-(3′,4′-diaminophenoxy)phenyl]-1-(3″-trifluoromethylphenyl)−2,2,2-trifluoroethane (6FTA) and 1,1-bis[4-(3′,4′-diaminophenoxy)phenyl]-1-[3″,5″-bis(trifluoromethyl)phenyl]-2,2,2-trifluoroethane (9FTA) were synthesized and characterized. A series of fluorinated aromatic polybenzimidazopyrrolones (polypyrrolones, PPys) were synthesized via a two-step polycondensation procedure. The inherent viscosities of the precursors, poly(amide amino acid) (PAAA), ranged from 0.39 dL/g to 0.54 dL/g. All the FPPys were amorphous. The freestanding FPPy films could be prepared, which exhibited good thermal stability with the glass transition temperature of 315-389°C, the temperatures of 5% weight loss ( T5%) of 497-535°C in nitrogen and residual weight retention at 700°C over 60%. All the FPPy films exhibited excellent alkaline-hydrolysis resistance which retained their original shapes and toughness after boiling 7 days in 10% sodium hydroxide solution. Also after boiling 8 h in 10% sodium hydroxide solution, the tensile strength could retain as high as 56% of the original values. The alkaline-hydrolysis resistance was much better than the polyimides which had similar chemical structures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40041. [ABSTRACT FROM AUTHOR]

The article presents a study on the tribological behavior of short-fiber-reinforced polyimide (PI) composites under water-lubricated and dry-sliding conditions. The researchers recrystallized 4,4'-methylenedianiline (MDA) in anhydrous ethanol and purified p-Phenylenediamine (p-PDA) by vacuum sublimation. They also prepared PIs by in situ polymerization of monomer reactants (PMR). They found that the initial friction coefficients of a PI resin and its composites were higher under dry sliding.