EFFECTS OF ANNEALING ON RELAXATION BEHAVIOR AND CHARGE TRAPPING IN FILM-PROCESSED POLY(PHENYLENE SULFIDE)

The relaxation behavior of poly(phenylene sulfide) (PPS) Ryton(TM) fil m has been studied as a function of annealing temperatures, T-omega ra nging from 30 degrees C to 140 degrees C. Previously, this type of sem icrystalline PPS film was shown to possess a very large fraction of co nstrained, or rigid, amorphous chains. Here we investigate relaxation of amorphous chains using differential scanning calorimetry (DSC), dyn amic mechanical analysis (DMA), and thermally stimulated depolarizatio n current (TSDC). DSC studies suggest that annealing causes the as-rec eived PPS film to relax some of its rigid amorphous fraction and incre ase its crystallinity, for T-a > T-g. DMA results show a corresponding increase in the temperature location of the dissipation peak and a de crease in its amplitude when T-a increases above 100 degrees C. Analys is of the TSDC rho-peak due to injected space charges trapped at the c rystal/amorphous interphase provides additional information about amor phous phase relaxation. This peak does not exist in amorphous him, or as-received film, or as-received films annealed at lower T-a. The rho- peak does exist in cold-crystallized films and as-received films annea led at higher T-a. We suggest that crystallinity is a necessary, but n ot sufficient, condition for observation of a rho-peak. In addition to crystallinity, the sufficient conditions for observation of a rho-pea k are existence of (1) a sharp and distinct crystal/amorphous interpha se, to provide charge trapping, and, (2) a large fraction of liquid-li ke amorphous phase, to provide a pathway for charge transport. These c onditions are not met in PPS semicrystalline films with very imperfect crystals and large amounts of rigid amorphous phase. In such films, t he rigid amorphous phase has, like the crystal phase, a restricted mol ecular mobility that causes it also to restrict the mobility of space charge. The implications are that film PPS processed with a large amou nt of rigid amorphous phase chains will have superior barrier properti es to the build-up of interfacial space charge. (C) 1996 John Wiley & Sons, Inc.