The Preparation Of Dynamically Vulcanized Thermoplastic Elastomer/organoclay Nanocomposites

Thermoplastic vulcanizate/organoclay nanocomposites were prepared through in. situ dynamic vulcanization. The morphology and properties of the nanocomposites were studied with X-ray diffraction (XRD), transmission electron microscope (TEM) et al. The mixing sequence of material affected the mechanical properties. In order to increase the compatibility between OMMT and polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) matrix and to enlarge the gallery of silicate layeres, maleic anhydride grafted polypropylene (PP-g-MA) was added during preparation of thermoplastic eiastomer/organoclay nanocomposites.Organic modification' could enhance the compatibility of montmorillonite with PP-EPDM based elastomer. XRD and TEM suggested a successful preparation of thermoplastic elastomer/organoclay nanocomposites. The dynamically cured samples showed improved tensile strength when organo-modified clay was added. In comparison with pure TPV, the tensile strength of the nanocomposites containing 2.8 wt% OMMT increased 27%, and the increase in elongation at break was about 65%. However, the improvements in the mechanical properties would be decreased when the content of OMMT increased. When OMMT was first mixed with EPDM, the enhancement in tensile strength was 40%, and the increase in elongation at break was about 75% at the loading of 5 wt% OMMT.Effect of the ratio of EPDM/ PP on the properties of the nanocomposites was investigated. When the ratio of EPDM/PP was 70/30 by wight, the nanocomposite showed high mechanical properties. While as the content of phenolic resin was 1.5 wt% of EPDM, the morphology of TPVs was obtained.The content of OMMT on the influence of morphology and properties of the nanocomposite was studied. The results showed that OMMT helped to breakup elastomer particles and prevent its coalescence, and the aspect ratio increased with OMMT content. OMMT preferentially was located at the boundary between PP and EPDM phase. However, when the content of OMMT reached 5 wt%, OMMT began to aggregate; when OMMT was added into EPDM first, most of OMMT was dispersed in EPDM phase. In this case, OMMT did not aggregate, and the nanocomposites showed excellent mechanical properties. Effect of PP-g-MA on the dispersion of OMMT and the distribution of OMMT was also investigated. Addition of PP-g-MA led to uniform distribution of OMMT in the matrix, which suggest the good compatibility between OMMT and PP/EPDM matrix. This resulted in enhancement of the modulus of the nanocomposites, while the tensile properties remains the same, which may result from OMMT mainly distributed on the PP matrix. Moreover, the decrease of viscosity through adding of PP-g-MA resulted in larger elastomer particles.The torque-time curve indicated that adding OMMT affects the vulcanization reaction of the composites and the crosslinking density, and the influence was relate to the distribution of OMMT in the nanocomposites.Dynamic mechanic analysis showed that the change of glass-transition temperature (T_g) of the EPDM and PP in the TPV nanocomposites was determined by the distribution of OMMT in the nanocomposites. The reduction in the damping behavior within the rubber transition temperature suggested stronger interaction between polymer and filler and the hindered cooperative motion of the polymer chains in the constrained environment.