Causes of rubber scorch

Update:25-08-2018
Summary:

The scorch of rubber is a kind of advanced vulcanizatio […]

The scorch of rubber is a kind of advanced vulcanization behavior, that is, pre-vulcanization phenomenon occurring in various processes before vulcanization (smelting, compound storage, extrusion, calendering, molding), so it can also be called early vulcanization.

Reasons for the scorch phenomenon:
(1) Improper formulation design, unbalanced vulcanization system configuration, and excessive use of vulcanizing agents and accelerators.
(2) For some rubber types that need to be masticated, the plasticating is not up to the requirement, the plasticity is too low, and the rubber is too hard, which causes a sharp rise in the rubber mixing. The temperature of the rubber mixer or other roller devices (such as the refiner and calender) is too high, and the cooling is not enough, which may also cause burns on site.
(3) When the rubber compound is unloaded, the film is too thick, the heat is not good, or it is not cooled, that is, it is stored in a hurry, and the storage of the warehouse is poor, the temperature is too high, etc., causing heat accumulation, which will also cause scorch.
(4) In the process of storage of rubber materials, the management is not good. After the remaining scorch time is exhausted, it is still piled up and there is no natural scorch.

Ways to prevent scorch:
(1) The design of the rubber compound should be appropriate and reasonable. For example, the accelerator should be used in multiple ways. Scorch the scorch. In order to adapt to the high temperature, high pressure and high speed rubber mixing process, an appropriate amount (0.3 to 0.5 parts) of scorch retarder can be used in the formulation.
(2) Strengthen the cooling measures for the rubber in the rubber mixing and subsequent processes, mainly by strictly controlling the machine temperature, the roller temperature and ensuring a sufficient cooling water circulation, so that the operating temperature does not exceed the critical point of the scorch.
(3) Pay attention to the management of semi-finished products of rubber materials. Each batch of materials should be followed by a flow card, implement the principle of “first-in-first-out” storage, and stipulate the maximum retention time of each material, and must not exceed. The warehouse should have good ventilation.

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