An atomistic molecular dynamic model to study the properties of LLDPE and wax

Abstract

Wax is often physically mixed with linear low-density polyethylene (LLDPE) to form a new polymer material. However, the morphology of these materials has not been described sufficiently, because molecular interaction at an atomic level was inadequately studied. Molecular dynamics (MD) simulation, using the Material Studio software as a computational tool, was available to develop models for wax and LLDPE to study their properties at an atomistic level. The models were validated by comparing the properties, such as solubility, density, and transition temperature, obtained with the models, with those obtained from experiments. After validation, the application of the model showed that the branch content of modelled LLDPE affected the glass transition temperature when the branch content was 70 per 1000 carbons for models with different branch lengths. The longer the branch length, the higher the glass transition temperature of LLDPE. However, the solubility parameter was unsuccessful in finding the length of LLDPE required to represent a single chain, because the properties of a copolymer are affected by the length of the chain, the number of branches, and their distribution on the backbone. The chain length of the wax showed no relationship to the solubility parameter in the solid state or in the melt. There was a decrease in the solubility parameter of the modelled LLDPE with an increase in temperature. The LLDPE and wax properties, examined through MD simulations, were within 10% of the experimental values.