Abstract
The thermoplastic vulcanizates (TPVs) of polypropylene (PP)/silicone rubber (SR) were prepared by dynamic vulcanization (DV) technology. The mixing torque, morphology, viscoelasticity, and creep response of PP/SR TPVs were investigated by torque rheometer, scanning electron microscope (SEM), transmission electron microscope (TEM), rotational rheometer, and dynamic mechanical analysis (DMA). A mixing-torque study showed that torque change and dynamic-vulcanization time increased with SR content increasing in the DV process, but DV rate was independent of SR content. TEM images indicated that the phase inversion of PP/SR-60 TPV from bicontinuous to a sea–island structure took place in the DV process, and a hot press would break the rubber aggregates and shrink a large SR phase. Dynamic-strain measurement demonstrated that PP/SR TPVs exhibit a distinct “Payne effect”, which can be attributed to the destruction and reconstruction of SR physical networks. Complex viscosity indicated that SR content did not affect the processability of PP/SR TPVs at high shear rates. Furthermore, the creep deformation and recovery of PP/SR TPVs at solid and melt states were studied, respectively.
Highlights
Thermoplastic elastomers (TPEs) are polymers that exhibit rubbery properties at using temperature and melt processability above melt temperature
There are two main kinds of TPEs, the block copolymer that has “soft” and “hard” segments, and the thermoplastic vulcanizate (TPV), prepared by dynamic vulcanization, where the curing of rubber occurs during mixing with plastic under a high temperature and shear [1]
To achieve high or functional performance, various TPVs were prepared by mixing different plastic phases and rubber phases, such as polyamide 6 (PA6)/EPDM [11,12,13], PA12/bromobutyl rubber (BIIR) [14], PP/ethylene octene copolymer (EOC) [15,16], poly(lactide) (PLA)/natural rubber (NR) [17], PLA/ethylene-co-vinyl acetate (EVA) [18], PLA/bio-based polyester [19], and thermoplastic polyurethane (TPU)/ NR [20]
Summary
Thermoplastic elastomers (TPEs) are polymers that exhibit rubbery properties at using temperature and melt processability above melt temperature. There are two main kinds of TPEs, the block copolymer that has “soft” and “hard” segments, and the thermoplastic vulcanizate (TPV), prepared by dynamic vulcanization, where the curing of rubber occurs during mixing with plastic under a high temperature and shear [1]. The composition ratio, the viscosity ratio of rubber and plastic, and the curing agents (curing rate and extent) could influence the DV process and determine the final morphology and properties of the TPV products. In order to control the final structure and properties of PP/SR TPVs, morphology evolution and rheological behavior were investigated in this study. The specific objectives included studying the mixing torque and morphology evolution of PP/SR blends at different dynamic-vulcanization stages, and investigating the influence of the PP/SR ratio on the viscoelastic and creep behaviors of PP/SR TPVs
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