Modelling the creep of cross-linked polystyrene in view of the relaxation aspect of strain

Viscoelastic models constructed from the relaxation perspective (VR) are applied to investigate the creep behavior of cross-linked polymer. The creep functions have been given by accumulating the strain of the components with different relaxation times described using distribution functions underlying different relaxation models. The fitting results of conventional Zener, fractional derivative Zener (FDZ) and VR models based on different distribution functions of relaxation time (DFRT) are compared. The results show that all the VR models can accurately describe the creep behavior of cross-linked polystyrene (CPS). The fitting qualities of the VR models using DFRT underlying Cole-Cole (CC) and Havriliak-Negami (HN) relaxation models are better than those of Kohlrausch-William-Watts (KWW) and Cole-Davidson (CD) relaxation models. The fitting result using VR model using DFRT underlying HN relaxation model is the best and may afford the information of change of distribution of relaxation time of CPS near its glass transition region.