Small‐angle x‐ray scattering and crystallization kinetics of poly(ethylene terephthalate) crystallized in a liquid environment

Abstract

SynopsisBy small-angle x-ray scattering, a systematic investigation was performed of the long spacing of poly(ethy1ene terephthalate) (PET) crystallized in a liquid environment. The results indicated that the measured long spacings were temperature dependent and apparently relatively insensitive to liquid type under the conditions studied. The kinetic nucleation model of polymer crystallization was found to adequately explain this dependence. The differences in the long spa&ngs between thermal and liquid-induced crystallization were in part rationalized in terms of the suspected supercoolings involved in the respective processes. Calculation of the spherulite growth rates for liquid-induced crystallization was made on the basis of the kinetic nucleation model and the classic theory of polymer-diluent crystallization. The results were shown to agree with inferential experimental observations of these growth rates and to elucidate the physics underlying liquid-induced crystallization. Finally, use of this growth rate theory in conjunction with a previous model for overall crystallization kinetics was shown to adequately describe and predict the diffusion-limited kinetics observed experimentally for most liquid-induced crystallization situations.1 -X ( t ) = exp(-Ktn)

Study of different effects on foaming process of biodegradable PLA/starch composites in supercritical/compressed carbon dioxide

“…At higher pressure under isothermal condition, the absorption of more CO 2 results in substantial swelling of polymer and profound plasticization effect to polymer which favors polymer chains rearrange themselves into a lower free energy. [27][28][29] Similarly, the higher temperature under isobaric conditions contributes to increasing mobility of polymer chain segments and a longer period for crystalline growth, so the crystallinity of polymer ascends markedly too. [27][28][29][30][31] In this study for the PLA/starch composites, from Figure 4, the areas of the fusion peak of virgin and foamed composite are 22.81 and 30.98 J/g, respectively.…”

“…[27][28][29] Similarly, the higher temperature under isobaric conditions contributes to increasing mobility of polymer chain segments and a longer period for crystalline growth, so the crystallinity of polymer ascends markedly too. [27][28][29][30][31] In this study for the PLA/starch composites, from Figure 4, the areas of the fusion peak of virgin and foamed composite are 22.81 and 30.98 J/g, respectively. According to the equation X C 5 DH f /DH F0 , (where X C is the crystallinity, DH f is the fusion heat of foamed sample, DH F0 is the fusion heat of virgin sample), the heat of fusion is proportional to the crystallinity of polymers.…”

Solvent Texturing of Polyester Yarn

“…Taking 67 °C as Tg2 (PET) and -100°C as T., ( CH2C12 ) , and the value of 1 / 4 as K [ 7 ] , we obtained a dependence of Tg on composition ( Figure 5). The lowering of Tg to 10*C is achieved with approximately 139~ CHZC12.…”

Supercritical CO2 assisted processing of polystyrene/nylon 1212 blends and CO2‐induced epitaxy on nylon 1212

“…The interaction between the polymer and the solvent reduces the effective glass-transition temperature (T g ), and if the reduction of T g is large enough to put the system in the crystallization temperature region, the polymer chains rearrange themselves into a lower free energy state. 23,24 Chiou et al, 25 Johnston and coworkers, 26,27 and Mizoguchi et al 28 all discovered that SC CO 2 can induce crystallization in polymers. In our study, the WAXD method was used to determine possible changes in the nylon 1212 aggregation structure after CO 2 absorption.…”