Strain-induced crystallization of poly(ethylene terephthalate)

摘要: The fabrication of poly(ethylene terephthalate), PET, into fibers, films, and containers usually involves molecular orientation caused by strain, which may lead to stress- or strain-induced crystallization (SIC). SIC PET was studied the methods birefringence, density, thermal analysis, light scattering, wide-angle X-ray. development crystallinity is discussed in relation rate crystallization, residual degree orientation, stress relaxation. experimental procedure stretching samples at temperatures above glass transition temperature, Tg, a given extension ratio specific strain an Instron machine. At end stretching, sample annealed stretched state temperature for various periods time, after quickly quenched room subsequent measurements. During relaxation curves are recorded. results indicate that annealed, can proceed three different paths depending on orientation. low as indicated birefringence value, annealing leads only relaxation, resulting decrease birefringence. intermediate levels, causes initial followed gradual increase finally leveling off fairly long period time. higher rapid before off. interpretation made using measurements differential scanning calorimetry, also terms data analysis.