Scorch is the early vulcanization phenomenon of rubber in the process of storage or processing, when the rubber material is scorched, the film is locally vulcanized, and elastic bumps appear on the surface, which affects the surface quality and physical and mechanical properties of rubber products. The main cause of rubber scorching is the improper design of the vulcanization system; When selecting the vulcanization system for the formulation of reclaimed rubber products, the scorching performance of the accelerator itself needs to be considered first.
1. Varieties and functions of commonly used accelerators for reclaimed rubber
Reclaimed rubber accelerators mainly include sulfonamides, thiazoles, thiurams and dithiocarbamates. The structure of the rubber accelerator contains anti-scorch functional groups (such as -S-S-, etc.) E4LYY617 auxiliary anti-scorch groups (such as carbonyl, carboxyl, sulfonyl, phosphoryl, thiophosphoryl and benzothiazole groups), which help to improve the scorching performance of reclaimed rubber. The type, dosage, and processing temperature of recycled rubber accelerator will affect the safety of reclaimed rubber scorching.
2. The length of scorching time of common rubber accelerators
(1) Sulfonamide accelerator: It has the characteristics of long scorching time, fast vulcanization rate, flat vulcanization curve and good comprehensive performance, which is suitable for the vulcanization of thick products of recycled rubber and can improve the processing safety of reclaimed rubber.
(2) Thiazole accelerators: the scorching time is short, but the vulcanization rate is fast; It is suitable for reclaimed rubber products that need to be vulcanized quickly, but it is necessary to pay attention to controlling the dosage to avoid excessive burning.
(3) Chiuram accelerator: high thermal stability, suitable for recycled rubber products that need to be processed for a long time, which can prolong the scorching time of reclaimed rubber and improve processing safety.
(4) Dithiocarbamate accelerator: it can shorten the scorching time and increase the vulcanization rate; Suitable for low unsaturation rubbers (e.g. IIR, EPM, EPDM) as well as in unsaturated rubbers that are vulcanized at low temperature or at room temperature.
The scorching time of commonly used accelerators is increased in the following order: ZDC
3. Regenerated rubber accelerator is used together
When using reclaimed rubber to produce rubber products, the combination of several accelerators is more beneficial to the processing safety of rubber compounds. For example, the accelerator TMTD has a very short vulcanization induction period, which can make the rubber material vulcanized rapidly; It can be used in combination with hyposulfonamides (such as CZ) and thiazoles (such as DM), which can effectively prevent scorching; The accelerator TMTD cannot be used in combination with accelerator D or dithiocarbamate, and the scorch resistance of the reclaimed rubber compound becomes poor.
The selection of appropriate accelerators in the production of reclaimed rubber products is very important to improve the scorching performance of reclaimed rubber and the comprehensive performance of reclaimed rubber products. In actual production, it is necessary to select the appropriate accelerator and dosage according to the type, processing conditions and application requirements of reclaimed rubber to achieve the best scorching performance and vulcanization effect, and improve the performance and production efficiency of recycled rubber products.
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