NR/SBR/organoclay nanocomposites: Effects of molecular interactions upon the clay microstructure and mechano-dynamic properties

A Novel Approach for Simulation and Optimization of Rubber Vulcanization

The kinetic model, encompassing the curing and reversion phenomena of the NR/SBR rubber vulcanization process, was developed by means of the finite element method simultaneously with heat transfer equations, including heat generation due to curing reactions. The vulcanization simulation was conducted for three spheres of different diameters (1, 5 and 10 cm) and two rubber wheels, one of which was a commercial product of the rubber industry. The proposed advanced simulation model, based on products’ two-dimensional axisymmetry, includes cooling after vulcanization, during which the crosslinking reactions continue to take place as a result of the products’ heated interiors. As a criterion for removing the product from the mold, an average vulcanization degree of 0.9 was set, whereby, during cooling, the vulcanization degree increases, due to crosslinking reactions. Based on the minimal difference between the maximal and minimal vulcanization degrees, which did not exceed a value of 0.0142, the optimal process parameters for each product were determined, achieving homogeneity and obtaining high-quality rubber products, while simultaneously ensuring a more efficient vulcanization process and enhanced cost effectiveness for the rubber industry.

Nanocomposites based on thermoplastic polyurethane, millable polyurethane, and organoclay: effect of organoclay content

Dynamically vulcanized thermoplastic polyurethane/millable polyurethane blend and its organoclay-based nanocomposites with co-agent assisted peroxide curative system were prepared by melt intercalation technique using batch mixer followed by compression molding to make sheets. Fourier transform infrared spectroscopy analysis revealed the presence of interfacial interactions due to hydrogen bonding of PUs with organoclays. X-ray diffraction and transmission electron microscopy analyses qualitatively established the uniform dispersion of organoclays within the PU matrix up to 5 phr Cloisite 30B (C30B) content and exhibited small aggregates at higher C30B loading. Mechanical testing reported significant improvement in tensile strength with addition of C30B up to 5 phr loading and then reduced a little but tensile modulus continuously increased with increase in C30B loading. Dynamic mechanical analysis (DMA) evaluated that the storage modulus ( E′) and glass transition temperature ( Tg) of both hard and soft segments of PU matrix substantially enhanced by incorporation of C30B. Thermogravimetric analysis revealed that the thermal stability of the PU matrix noticeably increased with C30B loading. Melt rheological characterization reported that all samples showed a strong shear thinning behavior within the scanned frequency range.