Kinetic Monte Carlo Simulations Of Polymer Cold Crystallization

Polymers can be crystallized by cold crystallization and hot crystallization,which are distinguished according to the direction of temperature change.Cold crystallization can be realized by quenching polymer melt to glass state and then heating it up to above the glass transition temperature.Cold crystallization in the low temperature region yields much smaller crystallites with less perfect crystalline structures,which benefits the industrial processing of polymer materials with a better transparency or a higher toughness,and thus is worthy our investigations.In order to study the cold crystallization of polymers,we introduce the diffusion barrier of polymer chain segments based on the previous dynamic Monte Carlo simulation method of polymer crystallization,which better reflects the characteristics that crystallization in low temperature region is mainly controlled by diffusion.In addition,the new simulation method also considers the energy barriers that need to be crossed when trans-conformation or gauche-conformation in a polymer chain changes from each other.The simulation method considering these two energy barriers is called the dynamic Monte Carlo simulation of polymer crystallization.In the first two chapters,the basis of crystallization-related polymer physics and the Monte method are briefly introduced.And in the third chapter,we systematically explored the effect and reasonable range of each energy parameter in the new simulation method,and determined a set of representative energy parameters in this range.Then we simulated the non-isothermal crystallization and isothermal crystallization process to study the crystallinity,chain motion characteristics and morphology of crystalline region of the system.The simulation results appear in consistence with our common experimental observations.The work in this paper extends the simulation temperature range to the low temperature region,which paves the way for studying the different crystallization modes of polymer,such as cold crystallization and hot crystallization,as well as stretching of polymer in low temperature region by Monte Carlo simulation.