THE CONTROL OF MISCIBILITY OF PP EPDM BLENDS BY ADDING IONOMERS AND APPLYING DYNAMIC VULCANIZATION/

The control of miscibility for isotactic polypropylene (PP) and ethyle ne-propylene-diene terpolymer (EPDM) has been attempted by adding poly (ethylene-co-methacrylic acid) (EMA) ionomers and by applying dynamic vulcanization. The theological properties, crystallization behavior, a nd morphology of the dynamically vulcanized EPDM/PP/ionomer ternary bl ends were investigated with a Rheometrics dynamic spectrometer (RDS), a differential scanning calorimeter (DSC), and a scanning electron mic roscope (SEM). Two kinds of EMA ionomers neutralized with different me tal ions (Na+ and ZN(++)) were investigated Blends were prepared on a laboratory internal mixer at 190 degrees C. Blending and curing were p erformed simultaneously, i.e., EPDM was vulcanized with dicumyl peroxi de (DCP) in the presence of PP/ionomer. The composition of PP and EPDM was fixed at 50/50 by wt% and the contents of EMA ionomer were varied from 5 to 20 parts based on the total amount of PP and EPDM. It was f ound that the addition of ionomers and the application of the dynamic vulcanization were effective in enhancing the miscibility of PP and EP DM. The structure of the blends was controlled by the following three component phases, i.e., the phase of the dynamically vulcanized EPDM, FP, and Zn-neutralized ionomer. The ternary blends showed more miscibi lity than the PP/EPDM binary blend. This is due to the thermoplastic i nterpenetrating polymer network (IPN) of the ternary blends. The struc ture and properties of the ternary blends differed, depending on the t ypes and contents of ionomer, i.e., the ternary blend containing Na-ne utralized ionomer did not show a thermoplastic IPN structure clearly, even though the blend was prepared by dynamic vulcanization. The terna ry blend containing Zn-neutralized ionomer clearly showed the behavior of a thermoplastic IPN when the contents of ionomer and DCP were 15 p arts and 1.0 part, respectively.