Effect of rigid amorphous phase on glass transition behavior of poly(trimethylene terephthalate)

In this work, a three-phase model consisting of crystalline, mobile amorphous and rigid amorphous phases (RAP) was used to describe the structural formation of poly(trimethylene terephthalate) (PTT) at various crystallization conditions. The variation in thickness and fraction of each phase was studied on both crystallization temperature Tc and crystallization time tc effects from differential scanning calorimetry and small angle X-ray scattering analyzes. The results showed that the rigid amorphous fraction and thickness of PTT increased with increasing Tc. Meanwhile, there is no remarkable change in crystalline fraction and thickness, and long period. A characteristic length ξa for cooperative motion of polymer chains in amorphous phase was determined from the variation in glass transition interval using dynamic mechanical analysis. The change in this length scale of glass transition was considered to be correlated with the variation in the thickness of rigid and mobile amorphous phases. The Tg of PTT increases and the relaxation peak becomes broader at high temperature flank with Tc. These facts are considered due to that the RAP formation leads to the suppression of cooperative motion for amorphous chains.