Highly Efficient Methods For Sulfur Vulcanization Techniques, Results And Implications

The rubber industry is a success story in the manufacturing endeavor of mankind. It started from a tree that was grown in the tropical South America and then the rubber production spread to tropical countries in other parts of the world. The rapid expansion of the rubber industry and the range of products that it produces is truly astonishing. Rubber is a fascinating material to study because of its unusual properties. It is even more amazing that so many products for so many applications are made using rubber. The success of rubber is due to the availability of a range of chemicals to cure or vulcanize it for industrial use. The chemicals known as accelerators and activators play a major part in the sulfur vulcanization of rubber. These chemicals and elementary sulfur are added to the raw rubber and heated to a high temperature to produce crosslinks that give shape stability to the vulcanized rubber. It is customary to add one or two accelerators and two activators with elementary sulfur to complete the cure. In recent years, the harmful effects of these chemicals and their adverse impacts on the environment have received a lot of attention. This poses a major challenge to the manufacturers and users of the rubber chemicals and urgent steps must be taken to meet these challenges. In this book, two new methods are described and supported by extensive experimental results that address this problem and offer a way forward. These methods measure the amounts of a sulfur-donor thiuram accelerator and a sulfenamide thiazole accelerator needed to provide monomolecular coverage of zinc oxide based on the approximate surface areas of the zinc oxide and the accelerator molecules used. These methods use zinc oxide with only one accelerator and no stearic acid to produce two single additives, that can efficiently cure rubber, despite using fewer chemicals. The additive made from the sulfur-donor thiuram accelerator does not require elementary sulfur and can replace the more traditional two accelerators, two activators, and elementary sulfur in the cure system of rubber formulation. Some studies have shown that the mechanical properties of the rubber vulcanized with this new additive to be outstanding, and in some cases, even superior to the ones reported before for the same rubber. This is a departure from the past when efficiency in sulfur vulcanization was achieved by using a high volume of these chemicals. A few sulfur-donor accelerators that exist produce highly toxic nitrosamines during high-temperature mixing and curing. When safer accelerators are on hand to treat the zinc oxide, a suitable single additive will be available to replace the current sulfur cure systems in industrial rubber formulations. This will bring huge benefits to the manufacturers and users of these chemicals. It is preferable to use zinc oxide to determine the precise amount of the accelerator required for a satisfactory cure rather than relying on outdated methods that need to be modified. A software is also developed to help with the selection and management of zinc oxide and the accelerators for the sulfur vulcanization of rubber. It is time to leave behind the old ways that served us so well and embrace a modern approach to the use of these chemicals in sulfur vulcanization.