Dynamically vulcanized PP/EPDM blends with balanced stiffness and toughness via in-situ compatibilization of MAA and excess ZnO nanoparticles: Preparation, structure and properties

It is a challenge to simultaneously improve the stiffness and toughness of polymer blends due to that the stiffness and toughness are two mutually exclusive attributes. In this paper, we successfully prepared dynamically vulcanized polypropylene/ethylene-propylene-diene rubber (PP/EPDM) blends with balanced stiffness and toughness through in-situ compatibilization of in-situ formed zinc dimethacrylate (i-ZDMA). The i-ZDMA came from the neutralization of methacrylic acid (MAA) and excess zinc oxide (ZnO) nanoparticles. With i-ZDMA, strong PP/EPDM interface and size reduction of EPDM particles were achieved during peroxide-induced dynamic vulcanization. The average size of EPDM particles was reduced to 260-280 nm, which significantly enlarged PP/EPDM interfacial surfaces. At the same time, the residual excess ZnO nanoparticles migrated into PP phase and served as nucleating agents to increase the crystallinity of PP phase. When the MAA/ZnO reached 2/1.3, the Izod impact strength was increased to 80.1 kJ/m(2), nearly 1.6 times that of the blend without i-ZDMA and 22 times that of neat PP, while the Young's modulus and yield stress were increased to 373 MPa and 14.8 MPa, respectively, showing an improved rigidness of blend.