The phase transition behavior of polybutene in partial melting/polybutene/polypropylene

Polybutene (PB) is a typical polymer with various crystal forms: I, II, III, and I′. Among them, the mechanical properties of Form I PB is better but only Form II crystal can be obtained from the melt due to the kinetic advantage and then transform to Form I slowly. While the slow phase transition rate restricts its application. Partial melting is applied to accelerate the phase transition, which was studied by Flash DSC. The results indicated that the phase transition behavior during partial melting shows dependence on the isothermal crystallization temperature and 70 °C is optimal, which can reduce the phase transition time from 20 h to 200 s. As the crystallization temperature determined, stepwise crystallization was used to accelerate the phase transition. The influence of nucleating temperature and time was investigated and the results indicated that 0 °C and 2 s are the best temperature and time, respectively. With stepwise crystallization, the phase transition time was further reduced to 50 s. Moreover, stepwise crystallization can increase the content of Form I crystal from 80.0% to 98.2%. The mechanism of phase transition during partial melting was proposed according to the results, which can supplement the existing phase transition mechanism.