There are typically three methods for preparing TPV: melt blending, solution blending, and latex blending. Among these, melt blending is the most common, utilizing primarily two types of equipment: internal mixers or twin-screw extruders. Depending on the specific process requirements, either a single type of equipment may be used independently, or both may be employed in combination. In industrial practice, twin-screw extruders have become the most widely adopted equipment for dynamic vulcanization; this is largely due to their capacity for continuous production, which ensures consistent product quality.
The specific steps involved in dynamic vulcanization are as follows: First, the rubber and plastic components are melt-blended within an internal mixer. Once thorough mixing is achieved, a vulcanizing agent is introduced; at this stage, vulcanization proceeds simultaneously with the mixing process. To ensure that the resulting blend exhibits excellent processing characteristics, the intensity of the mixing action must be correspondingly increased as the rate of vulcanization accelerates. Since granular forms of rubber are commercially available, it is not strictly necessary to use an internal mixer to blend the plastic and rubber; instead, a twin-screw extruder can be utilized directly for the mixing process. In terms of specific process design, dynamic vulcanization can be executed in a two-step sequence, wherein the plastic component is added in two separate increments to the rubber blend; this approach serves to protect the plastic from oxidative degradation induced by the vulcanizing agent during the dynamic vulcanization process.