Investigation of Mechanical and Hygroscopic Properties for the Semi-crystalline Polypropylene Polymer Via Experiments and Molecular Dynamics

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In this study, mechanical properties and moisture related hygroscopic characteristics of semi-crystalline polypropylene (PP) were investigated via molecular dynamics (MD) simulations and experiments with respect to degree of crystallinity. To control the degree of crystallinity, experimental samples were treated by an annealing process while MD models were constructed through combination of crystalline and amorphous layers. In order to evaluate crystal structure and calculate degree of crystallinity for the experimental samples, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) measurements were conducted. For comparison with the experimental samples, an XRD simulation was performed for the MD models. Then, the mechanical and hygroscopic properties such as elastic modulus and moisture saturation amount were studied with respect to the degree of crystallinity through experiment and MD simulation. It was found that the effects of the degree of crystallinity on the hygro-mechanical properties of the semi-crystalline PP can be predicted from the developed MD simulation. It is expected that the simulation approach developed in our study can be widely used to predict the characteristics of the semi-crystalline PP with varying degree of crystallinity.