subvulcanização

Subvulcanization refers to a premature and undesirable vulcanization process that can occur in rubber compounds during mixing or processing before the intended curing stage. It is characterized by a slight stiffening or scorching of the rubber, which can negatively impact its final properties. This phenomenon is primarily caused by excessive heat generated during mechanical working, or by the presence of certain highly active accelerators or other compounding ingredients that initiate the crosslinking reactions prematurely.

The onset of subvulcanization can be detected through rheological measurements, such as using a rheometer to observe an increase in torque or a decrease in viscosity at processing temperatures. Visually, the rubber may appear drier or exhibit a slightly gummy texture. The consequences of subvulcanization can range from processing difficulties, such as increased energy consumption and sticking to equipment, to a reduction in the physical properties of the vulcanized product, including lower tensile strength, elongation at break, and resilience.

To prevent subvulcanization, careful control of processing temperatures is essential. This involves efficient cooling of mixing equipment, using lower mixing speeds, and selecting appropriate accelerators and activators that provide a suitable scorch safety margin. The order of ingredient addition during mixing can also play a role in mitigating this issue. Understanding the causes and effects of subvulcanization is crucial for rubber compounders and processors to ensure consistent product quality and efficient manufacturing.