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ABSTRACT:Ethylene-propylene-diene functionalized with mercapto groups (EP-DMSH) was employed as compatibilizing agent for natural rubber (NR)/EPDM blends, resulting in a substantial increase of the ultimate tensile strength of these blends without affecting the elongation at break. There is also a decrease of the curing time with the addition of as low as 2.5 phr of EPDMSH, mainly in NR/EPDM (70:30 wt %) blend, indicating the accelerator effect of this functionalized copolymer. This copolymer also increased the crosslink degree and the gel content. From dynamic mechanical analysis (DMTA), it was demonstrated that EPDMSH improves the covulcanization process. The reactive compatibilization of EPDMSH was demonstrated by the presence of insoluble material in nonvulcanized/compatibilized blends and by its thermogravimetric (TGA) analysis.

Abstract. Thermoplastic elastomer based on polypropylene (PP) and acrylic rubber (ACM) was investigated, with special attention on the compatibilization and dynamic vulcanization. ACM component contains chlorine and carboxyl groups along the backbone, which act as center for the curing and reactive compatibilization. The last event was carried out by adding a combination of maleic anhydride-modified PP (PP-g-MA) and triethylene tetramine (TETA), which act as interfacial agents between PP and ACM phases. The effectiveness of the compatibilization was suggested from mixing torque and viscosity, determined from rheological measurements. Outstanding mechanical performance, especially elongation at break, and better tensile set (lower values) were obtained with the compatibilization. The dynamic vulcanization also resulted in good mechanical properties for compatibilized blends, but the performance was inferior to that observed for non vulcanized blends. The effect of the compatibilization and/or dynamic vulcanization on the dynamic mechanical, thermal, morphological and stress relaxation properties was investigated.

The effect of mercapto‐ and anhydride‐functionalized ethylene propylene diene rubber (EPDM) or ethylene–vinyl acetate (EVA) copolymers on the vulcanization kinetics of natural rubber/EPDM blends was investigated using the oscillatory disk rheometer. The mercapto groups in both EPDM and EVA copolymers resulted in a significant decrease of the curing time. The Coran's model was applied to set the kinetic constants within each distinct step of the vulcanization process. The highest curing velocity was perceived in a blend containing 2.5 phr of mercapto‐functionalized EVA. The functionalized EVA, especially that which was functionalized with anhydride groups, also displayed a lower solvent uptake on blending, which would imply an increase of the crosslink density as well a covulcanization phenomenon.

This work investigates the effect of different preparation routes including mechanical mixing and in situ polymerization of aniline on the electromagnetic interference shielding effectiveness (EMI SE) over the X-band (8-12 GHz) frequency range for polyaniline doped with dodecylbenzene sulfonic acid (PAni.DBSA) filled in styrene-butadiene-styrene triblock copolymer matrix. The dc conductivity and dielectrical properties were also investigated. For all systems, the electrical conductivity, dielectric constant, and EMI SE increased with the increase in the concentration of PAni.DBSA. Blends prepared by the in situ polymerization exhibited higher conductivity and dielectric constant and better EMI SE characteristics than the physical blends with similar amount of PAni.DBSA. EMI SE value as high as À35 dB has been achieved with about 30% of PAni.DBSA prepared by the in situ polymerization. Regarding physical blends, those involving PAni.DBSA prepared by a redoping process displayed better EMI SE. For all systems under consideration, the conductivity and EMI SE bear an exponential relationship that can be represented by a master curve.