Investigation On The Physical Aging Behaviors Of Polystyrene And Polystyrene/nanocaco₃Composites

Physical aging is a molecular chain rearrangement（relaxation） behavior of glassypolymer materials which occur during the storaged and employed process under itsglass transition temperature（Tg）. On the one hand, the physical aging behavior isinevitable, and it has a significant impact on the thermodynamic and mechanicalproperties which change the value and service life of materials. On the other hand, thephysical aging behavior occurs below the glass transition temperature and has relevancewith the glass transition. Thus, the relationship between the structure and performanceof the glassy polymer materials can be studied by the glassy molecular relaxation andtransition information received from the physical aging process. Therefore, the study ofphysical aging behavior of glassy polymer has potential practical significance forguiding the use of polymer materials; at the same time, it has very important theoreticalsignificance for understanding the glassy structure and its transition. However, withnormal temperature conditions, the obvious physical aging behavior of glassy polymermaterials can be observed after a molecular chain relaxation of decades, which farexeeded the acceptable time scale of experimental research. For the reasons given above,the physical aging behavior of glassy was studied by the way of simulation methods, inorder to achieving the effect and purpose of study in a relacively short period of time.In this paper, differential scanning calorimetry（DSC）, X-ray diffraction（XRD） andfluorescence spectra methods were used to explore the influence of physical agingbehavior on the relaxation process of the molecular chains of atactic polystyrene（α-Ps）;meanwhile, conduct a preliminary inquiry on the relaxation behavior of theα-Ps/Nano-CaCO₃composite materials after the physical aging, and use thecorresponding theory analysising, explaining the results of the study.The experimental results show that: the physical aging process has a significantinfluence on the relaxation process of the atactic polystyrene. There is a positivecorrelation between the physical aging of α-Ps and the aging time（ta）. The phenomenonof the physical aging also shown a negative relevance between the physical aging andquenching rate. This phenomenon was explained from the perspective of the freevolume theory. The characteristic parameters of the relaxation process, such as: glasstransition temperature（Tg）, peak temperature（Tp）, the enthalpy, fragility parameter（m）and so show a certain relation with the aging time and the quenching rate.There is also a positive correlation between the physical aging of α-Ps/Nano-CaCO₃composite materials and the aging time; at the same time, theapparent activation energy of the glass transition process calculated by the TNMequation, and compare with the same aging conditions α-Ps, the α-Ps/Nano-CaCO₃composite materials have lower glass transition temperature（Tg） and apparent activationenergy（Ea） attributed to the Nano-CaCO₃dispersed in the composite has a positiveinfluence on the relaxation process of the PS molecular chains.