According to the Ministry of Science and Technology, the State Key Laboratory of Polymer Physics and Chemistry has made important progress in the crystallization and crystal transformation direction of polybutene-1. Research results have recently been published in the international top journal Macromolecules.
'Plastic gold' Polybutene-1 material has superior advantages over other polyolefin materials in terms of resistance to high temperatures, creep at low temperatures, and stress cracking properties, but after the melt has been processed, it has become a metastable crystal II. Then it spontaneously and slowly changes to stable crystalline form I at room temperature. This transformation leads to shrinkage of the product volume and non-uniform internal stress, which greatly restricts the application of this material.
Prof. Yongmeng Meng from the State Key Laboratory of Polymer Physics and Chemistry conducted a thorough study of the polybutylene-1 crystal transformation kinetics and the internal structure mechanism, through the melt temperature and crystallization temperature of butene-1/ethylene copolymer. Through the direct control of the melt, a stable crystal form I' was successfully obtained. The two-step annealing method designed by the research group resulted in a significant increase in the crystal transformation rate. By controlling the temperature of one step annealing, the crystal was first realized. The nucleation and growth kinetics characterization of the transformations gave the temperature dependence of the nucleation and growth during the crystal transformation. The optimum nucleation temperature was -10°C and the optimum growth temperature was 40°C. It provides the basis for the industry to reduce inventory time and speed up product circulation.
In the above study, the research group also found that the main factor that promotes rapid nucleation at low temperatures is the internal stress transmitted by the intercrystalline contact molecules, which originates from the relatively large shrinkage of amorphous regions during cooling. Provide theoretical guidance for product design and material selection in industry.