Abstract
Abstract The ethylene-propylene-diene monomer/polypropylene (EPDM/PP) thermoplastic elastomer is prepared by dynamic vulcanization. The effects of different rubber ratios and crosslinking agent contents on the static and dynamic mechanical properties, crystallization and rheological behaviors are investigated and discussed. EPDM/PP with the rubber ratio from 40 to 50 % and crosslinking agent content of 1.2 wt% has the highest tensile strength and elongation at break. The fracture morphologies indicate that EPDM/PP with high rubber ratios and crosslinker contents is over vulcanized to harden, which results in that some large particles cannot be fragmented by shear force. The crystallinity obtained from differential scanning calorimetry (DSC) shows a decrease with increasing rubber ratio and a very slight variation with increasing the crosslinking content. The dynamic mechanical analysis (DMA) results display a decrease trend in storage modulus and tan δ with increasing crosslinking density. The rheological behaviors show that the complex viscosity also increases with increasing crosslinking density, indicating that the elastic deformation becomes superior to viscous flow in EPDM/PP.
Highlights
Compared with traditional rubber materials, a thermoplastic elastomers (TPE) combining the high elasticity of rubber and toughness of the plastic show many distinct advantages in processing including low energy dissipation, high efficiency, high effective reclaiming
EPDM is fragmented into small particles dispersed in the matrix by the shearing force of the screw, and the free radicals generated by the crosslinker react with the allyl hydrogen on the pendant group of EPDM to form the net structure
The data of static mechanical properties show that the highest tensile strength and elongation at break are obtained when the rubber ratio is between 40 and 50 % and the dicumyl peroxide (DCP) content is kept at 1.2 wt%
Summary
Compared with traditional rubber materials, a thermoplastic elastomers (TPE) combining the high elasticity of rubber and toughness of the plastic show many distinct advantages in processing including low energy dissipation, high efficiency, high effective reclaiming. The main influence factors on the properties of EPDM/PP include the characteristics of PP, rubber (EPDM) ratio, degree of crosslinking and oil charging (Coran and Patel, 1980; Gupta et al, 2000; Winters et al, 2001; Ma et al, 2016). Among these factors, rubber ratio and degree of crosslinking are the most considerable. A proper crosslinking density is helpful to the fragmentation and dispersion of EPDM particles and a too high or low Intern. Polymer Processing XXXIV (2019) 4 Ó Carl Hanser Verlag, Munich
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