The potential of O-MMT as a reinforcing filler for uncured and dynamically cured PVC/XNBR composites

Organic montmorillonite modified with quaternary ammonium (O-MMT) was compounded with uncured and dynamically cured poly(vinyl chloride)/carboxylated nitrile butadiene rubber (PVC/XNBR) composites, using a Brabender Plasticorder at 130 degrees C and 50 rpm rotor speed. The reinforcing efficiency of the O-MMT was investigated in the uncured PVC/XNBR composite and the dynamically cured PVC/XNBR counterpart. Mixing and dynamic curing of the composites were monitored by typical torque-time curves derived from a Brabender internal mixer. The torque-time curves revealed that the dynamic curing process was successful and the incorporation of O-MMT has no adverse effect on the processibility of the composites. It has been found that the introduction of crosslinks within the rubbery phase in the presence of the O-MMT has further improved the tensile properties. DMA studies revealed that dynamically cured composite with O-MMT showed higher storage modulus than the composite without O-MMT. Furthermore, a one-step tensile modulus vs. temperature curve and a related one peak tensile loss modulus vs. temperature curve were obtained, consequently, both are characteristics of a miscible polymers system. Further evidence on the composite miscibility was purchased by thermal scans from DSC, which showed a single glass transition temperature of PVC/XNBR composites. This claim was further supported by ATR-IR spectra which revealed that hydrogen bonding is extensively involved in PVC/XNBR composites. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence, enhanced mechanical properties. Furthermore, we proved in our studies the reinforcing role played by layered clay due to better dispersion, as well as improved interactions.