Which of the following factors affects the properties of the vulcanizate?

The percentage of sulfur and accelerator used in the vulcanization process is critical in determining the properties of the vulcanizate. Vulcanization itself is a chemical process that involves adding sulfur to rubber, which creates cross-links between the rubber molecules, enhancing their strength, elasticity, and thermal stability.

The amount of sulfur dictates the degree of cross-linking: too little sulfur may lead to a vulcanizate that is stale and lacks sufficient strength, while too much can lead to brittleness and loss of elasticity. Accelerators are also crucial as they help to speed up the vulcanization reaction and can influence the efficiency of cross-linking, impacting the final mechanical properties of the rubber. Thus, the right balance of sulfur and accelerators is essential for achieving the desired performance characteristics in the final product.

Other factors, such as the thickness of the rubber sheet, type of base material, and initial rubber temperature, certainly play roles in the processing and functionality of rubber but have less direct influence on the fundamental chemical and physical changes that occur during vulcanization itself.