This study investigates (ZnO)s with different surface features as vulcanization activators in unfilled SBR vulcanizates. ZnO is termed the best activator due to its fast reaction kinetics. A high release of ZnO into the environment harms marine ecosystems, and most ZnO production goes to the rubber sector; therefore, reducing ZnO amount is essential. Active, nano and functionalized ZnO compared to conventional ZnO in SBR matrix; concentration optimized based on curing, mechanical, physical, and dispersion analyses. The Arrhenius equation approximated the cure curve's kinetic constant and activation energy. Crosslink density measured by swelling experiment and solvent freezing point depression. Nano ZnO was used from 0.5 to 2phr, active ZnO from 1 to 4phr, and functionalized ZnO from 1 to 3phr compared to 5phr of conventional ZnO. The tensile strength of N1.5, F1.5, and A2 SBR increased by 5%, 26%, and 18% compared to C5SBR, whose elongation at break improved by 30%, 7%, and 23%. The data were analyzed using tukey HSD post hoc test. Regarding mechanical properties and curing characteristics, 2phr active, functionalized, and 1.5phr nano ZnO is analogous to 5phr conventional ZnO in an unfilled SBR matrix. The quantity of ZnO in rubber vulcanizates decreased successively by 60%, 60%, and 70%.
A new generation conductive thermoplastic vulcanizates (CTPVs) have been developed and characterized in detail, which is based on ultra-high molecular weight (UHMW)-EPDM rubber combined with conductive carbon black (CCB) filler. The influence of incorporation of CCB filler in the CTPV matrix on various relevant properties has been studied thoroughly. Physicomechanical properties indicate a significant improvement in the tensile strength, modulus, crosslink density, and tear strength together with quite good flexibility of the CTPVs. Rheological properties depict excellent processability and material strength (storage-modulus and complex-modulus), and stress relaxation shows a higher relaxation time of the CTPVs over the pristine-TPV. Morphology study (AFM, FESEM, and TEM) reveals very well dispersion of the CCB-filler and droplet type dispersed morphology has been achieved. The study of the electrical properties demonstrates that fair AC conductivity can be achieved for high filler loading. AC impedance analysis also proves the improvement for CTPVs over the pristine TPV. It is well described that due to the incorporation of the CCB-filler, all the properties are improved, and from some of the results amount of CCB-filler can also be optimized.UHMW-EPDM/PP-based conductive TPVs (CTPVs) can be potentially used as a sensitive stretchable conductor for various applications.
Elastomeric compound development is a multi-objective optimization task, and it contains vulcanization packages that crosslink the matrix. The deciding factors for vulcanization systems are the nature of elastomer, service temperature, processing methods and vulcanizate properties. Accelerated sulfur and organic peroxide are examples of vulcanization systems; each has its advantages and shortcomings. The peroxide-based system shows a high level of temperature stability while its flexibility is inferior to sulfur vulcanization. This study is finetuning a hybrid vulcanization system containing a combination of ultra-fast accelerated sulfur and a peroxide system; it also optimizes the vulcanization package ratios concerning various rheological and vulcanizate properties with the help of the Taguchi method. Ethylene propylene diene rubber (EPDM) is chosen as the basic matrix due to its excellent viability and commercial application with both the vulcanization systems. The formulations are optimized to combine the advantages of both the vulcanization systems. The results indicate that the vulcanization is sulfur-driven, but peroxide influences by selecting the crosslink sites and type. The hybrid system uses more components, but proper optimization helps to reduce the quantity of vulcanization packages with an improvement in physio-mechanical properties; it also helps to reduce the discharge of carcinogenic accelerator by-products, such as nitrosamine.
Silica is the rubber industry’s most essential and cost-effective reinforcing filler after carbon black. The silica reinforcement mechanism with a non-polar elastomer is complicated by the presence of polar functional groups on the silica surface. This polar nature of silica causes filler-to-filler interaction by forming hydrogen bonds. Therefore, sizeable non-dispersed silica clusters remain in a non-polar rubber matrix. To avoid these strong filler-filler interactions and improve rubber/silica compatibility, the silica surface needs to be modified. This can be done using a coupling agent which has functional groups capable of linking both the rubber and silica. It has been discovered that when silica/silane coupling agents are present, the critical properties like rolling resistance and wet grip in the magic triangle of tire tread balance out better than carbon black formulations, bringing the system closer to the green tire goal. In this review article, the efforts made by both the rubber formulation development and chemistry to fully exploit the potential of silica/silane reinforcement for automotive tires are retrospected. Highlights on how compounding ingredients, process technology, functionalized elastomer, novel silanes, and the variant of silicas can enhance the magic triangle and silica-silane reaction mechanism are provided. In addition, the kinetics of silanization and measurements for the degree of silanization is also highlighted. Future research directions in this area are also touched upon. Hopefully, this review can stimulate future silica/silane scientific and technology developments for both academic and industrial-oriented requirements.
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