In fact, peroxide curing system - commonly used Organic peroxides crosslinking agent; Whether Organic peroxides is suitable as a crosslinking agent depends on the half-life of Organic peroxides and the type of free radicals generated by decomposition. Due to the limitation of rubber processing temperature and vulcanization temperature, the half-life of Organic peroxides as a crosslinking agent should be within the appropriate range. That is to say, the half-life should not be too short to avoid coking during the mixing stage. The half-life should not be too long to avoid high vulcanization temperature or long vulcanization time. Secondly, the free radicals formed after decomposition should have high reactivity, such as alkoxy groups, and high formability: the efficiency of crosslinking agents.
In terms of type, alkyl peroxides are most commonly used as cross-linking agents Organic peroxides, and ketal and diacyl peroxides are also used.
1. Dialkyl peroxide; Dialkyl peroxides typically have high crosslinking efficiency and require a higher curing temperature. Common dialkyl peroxides are dicumyl peroxide, bis (tert butylperoxyisopropyl) benzene, and 2,5-dimethyl-2,5-bis (tert butylperoxyisopropyl) hexane ethane.
Dicumyl peroxide, also known as DCP, is the annual consumption of Organic peroxides. The advantages of DCP are high cross-linking efficiency, low price, and cost advantage. The main drawback is that vulcanized products have a strong pungent odor. The source of odor is the decomposition product of DCP Acetophenone.
2. Peroxyketal; Compared to dialkyl peroxides, ketal peroxides typically initiate crosslinking at lower temperatures and are often used in products that require low-temperature crosslinking.
Di-tert-butyl peroxide -3,3,5-trimethylcyclohexane; Di-tert-butyl peroxide -3,3,5-trimethylcyclohexane is a common oxidative ketal crosslinking agent, commonly known as 3M. The characteristic of this peroxide is its low vulcanization temperature, which is very suitable for situations that require low-temperature vulcanization. The main drawback is that the vulcanization efficiency is slightly low, especially in saturated rubber, so the dosage is too large; And there is a trend of burning.
3. Diacyl peroxide; Compared with dialkyl peroxides, diacyl peroxides have a significant coking tendency, making it difficult to meet the processing requirements of most rubber, and the generated free radical activity is relatively low and weak. diacyl peroxides are easily affected by carbon black, making diacyl peroxides only used for crosslinking of silicone rubber.