The Mechanical Performance And Shear Thickening Behaviors Of Interfacial UV Crosslinked Thermoplastic/Lastomer Blends

In this thesis, from the preparation of interfacial UV crosslinked thermoplastic/elastomer blends material, to the relationship between the physical properties of the material and the material internal structure were researched. Main content mainly includes three aspects:1. An easy procedure to introduce the photocrosslinked interface for polypropylene (PP)/maleic anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS) thermoplastic/elastomer blends by UV radiation is reported. This procedure involves the free-radical crosslinking at the interface between mSEBS domain phase and PP matrix phase and in the mSEBS phase domains with benzophenone (BP) as the photoinitiator and triallyl isocyanurate (TAIC) as the crosslinking agent. Compared with absence of the photocrosslinking, the structured PP/mSEBS blends with photocrosslinked interface forcefully confirmed by rheological measurements demonstrate simultaneous enhancements of toughness and tensile strength because of the enhanced interfacial adhesion and the more rigid mSEBS particle-like phase domains due to photocrosslinking. For the comparison purpose, PP/ethylene-propylene-diene rubber (PP/EPDM) blends were subjected to the same studies, however, the above observed simultaneous enhancements of toughness and tensile strength for the mSEBS/PP blends are completely absent for the PP/EPDM blends, simply because the UV radiation-induced interfacial crosslinking between the dispersed EPDM phase domains and PP matrix phase does not occur.2. We firstly report a unique obvious shear thickening behavior for the melts of polymer blends consisting of maleic-anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS)or ethylene-propylene-diene copolymer (EPDM), and polypropylene (PP) components. Rheological and rheo-optical microscopy reveal that the "contact network" structure by increasing the elastomer content brings out this unique obvious shear thickening behavior in molten state. Shear-thickening for polymer blends is pertinent for developing applied techniques to enhance the mechanical strengths of polymer blends as well as for preparing high performance polymer blend composites.3. We report a unique obvious shear thickening behavior for which the viscosity increases by102-103folds with increasing shear stress for the melt of a thermoplastic/elastomer blend consisting of maleic-anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS) or ethylene-propylene-diene copolymer (EPDM), and polypropylene (PP) components treated by ultraviolet light (UV) radiation. Rheological and optical rheology measurements reveal that UV radiation-induced interfacial crosslinking between dispersed mSEBS phase domains and PP matrix phase for the PP/mSEBS blend with high mSEBS content producing the gel network structure of polymer melt, brings out this unique obvious shear thickening behavior in the molten state, compared with absence of the obvious shear thickening behavior for PP/mSEBS blend with low mSEBS content, as well as PP/EPDM blends without UV radiation-induced interfacial crosslinking, for which the formation of strong network does not occur due to the dilute mSEBS particles and large interparticle distances.