A Method for Predicting the Crystallinity of Linear and Branched Polyethylene ^†

ABSTRACT: The molecular parameters of polyethylene are characterized by its molecular weight distribution and the branching. Both strongly manipulate the crystalline state, which plays a key role in the predetermination of many product properties such as gas solubility, melting behavior, and tensile strength. This work addresses the question of how the crystallinity of polyethylene can be calculated as a function of molecular parameters (molecular weight and branching) and temperature. The basic idea is to transfer the so-called statistical car-parking problem (CPP) to polyethylene. However, this concept does not consider branching. Therefore, the CPP is coupled with the Flory approach for co-polymers (FCA), which explicitly considers branching. The coupled theory of CPP and FCA correctly predicts the crystallinity of branched polyethylene from molecular parameters and temperature, and reproduces the dependencies of the influencing variables observed in experimental data reported in the literature.