Toughening Polystyrene By Ethylene-Propylene-Diene Terpolymer (EPDM) And Exceed Fine Calcium Carbonate (CaCO₃)

Since Ostromislensky applied the first patent on the toughening of Polystyrene in 1927 and Dow Chemical Company exploited the continuum producing technique of high impact polystyrene in 1952, it has been an important task to obtain polystyrene alloys with good integrate properties by modification.The effect of toughening agent, Ethylene-Propylene-Diene terpolymer (EPDM) on the phase structure and mechanical properties of polystyrene (PS) was studied. Styrene-butadiene-styrene (SBS) was used as the compatibilizer. The notched charpy impact strength reaches to a maximum value of 26.3 kJ/m2 at the composition of PS/EPDM/SBS= 100/20/10, 20 folds comparing to 1.27 kJ/m2 of pure PS. Investigating the morphologies of the blend by scanning electron microscope (SEM) and transmission electron microscopy (TEM), we concluded that the increment of the mechanical properties is mainly due to the changes of EPDM phase structure that changed from irregular to spherical, until to interlocked morphology. Monitoring by butanone extraction and FTIR analysis, it is found that there is a graft reaction between PS and EPDM during compounding, it also reveals that the compatibility is promoted by the addition of SBS. Through dynamic rheologic analysis, it is found that there is strong interaction between the components among the systems. With the increment of EPDM content, the interaction is impoved; the modulus is also improved, while the loss factor is decreased.At the same time, melt blending attains the composites of Polystyrene (PS) and CaCO3 with different radium and different content. The impact strength of the composites are 60-80 percent higher than pure PS. Glass transition temperature (TK) are also increased. The PS/ nano-CaCO3 (100/2) composite has the highest impact strength and TK. Results of specific volume analysis and electron microscopic observation of different composites reveal that the free space of the composites decreases with addition of nano-CaCO3, inferring that the modification of the properties is strongly related to the decrease of the free space in the composites.