Crystal structural evolution of Polybutene-1 in solid state upon deformation and stress relaxation

The influence of strain rate on the deformation induced crystal transition from forms II to I of Polybutene-1 is investigated by in situ Wide Angle X-ray Diffraction at different temperatures. The structural evolution during the subsequent stress relaxation is further monitored. As strain rate increases, the phase transition rate decreases apparently, while the dependence on stress and strain also becomes weak. The phase transition during deformation with three strain rates shows consistent dependence on external work. The transition rate in terms of form I content drops instantly when stretching stops. Further analysis on the evolution of crystallinity and orientations of both forms II and I shows that a small amount of recrystallization occurs in form II during stress relaxation at 80 °C, accompanied by a continuous increase in the content of form I, which further confirms occurrence of deformation induced melting and recrystallization.