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How to control the foaming speed and vulcanization speed of EPDM sponge

The sponge rubber produced with EPDM reclaimed rubber has light texture, low density, good elasticity and high softness. It not only has excellent shock absorption,
sound insulation and heat insulation performance, but also has good resistance to light, heat, ozone, climate change. Among them, the sponge rubber with EPDM or reclaimed rubber as the main raw material has lower production cost and the higher cost performance. When EPDM or reclaimed rubber produces sponge rubber, it is very important to match the vulcanization speed and foaming speed.

Studies have shown that: when the vulcanization speed of EPDM sponge rubber is faster than the foaming speed, the viscosity of the rubber increases and it is difficult to foam; when the foaming speed is faster than the vulcanization speed, the gas is easy to run off and the foaming efficiency is reduced, resulting in a sponge problems such as insufficient foaming of rubber and non-smooth crust surface. Therefore, when rubber product manufacturers choose EPDM reclaimed rubber to produce sponge foam rubber, they need to choose a foaming agent with a suitable decomposition temperature according to the molding process to ensure that the decomposition of the foaming agent is carried out within a temperature range where the vulcanization temperature can be adjusted. The vulcanization speed and foaming speed of the EPDM sponge rubber can be adjusted by adjusting the setting of the foaming agent system and the vulcanization system.

1.Foaming agent system
During the actual production, it is more difficult to adjust the decomposition rate compared with the vulcanization rate.because the decomposition rate of the foaming agent is greatly affected by the compounding agent used in the compound. Generally, the vulcanization system of EPDM sponge rubber will be adjusted after the confirmation of foaming agent and adjust the vulcanization speed to adapt to its foaming speed. For example, when using EPDM reclaimed rubber to produce sponge foam hose,  it is necessary to adjust the types and amounts of various compounding agents in the vulcanization system to adapt to the foaming speed if you select the compound chemical foaming agent HCB as the EPDM sponge rubber.

  1. vulcanization system
The common vulcanization systems for EPDM rubber products include sulfur vulcanization systems and peroxide vulcanization systems. In the formulation of sponge rubber with EPDM reclaimed rubber as the main raw material, rubber product manufacturers can use DCP as the main vulcanizing agent and sulfur as the auxiliary vulcanizing agent, together with the accelerator TT and the accelerator DM to match the HCB foaming speed to better adjust the vulcanization speed and foaming speed. For example (in EPDM foam hose, you can use 3 parts DCP, 0.3 parts sulfur, 0.5 parts accelerator TT, 0.15 parts accelerator DM to mix with 10 parts foaming agent HCB, where the amount of raw rubber is calculated as 100 parts ). It should be noted that because EPDM reclaimed rubber processed from waste EPDM rubber products contains a small amount of compounding agents such as vulcanizing agents and accelerators, there is a certain difference between the effective rubber content and raw rubber. So rubber product manufacturers need to adjust the amount of compounding agent according to the actual situation.

The EPDM sponge rubber in different occasions has very different requirements for the performance of the rubber compound. Therefore, there is a certain difference between the selection of the EPDM reclaimed rubber product and the blending amount. The rubber product manufacturers must "differ according to needs" and choose the most appropriate EPDM reclaimed rubber, determine the reasonable dosage and adjust the blowing agent system and vulcanization system to match the foaming speed and vulcanization speed.