Some accelerators color rubber products due to their different colors, and some products are discolored by chemical action or sunlight exposure. These accelerators cannot be used in white or bright-colored products. Some accelerators have obvious odor and bitter taste, and some accelerators can also contaminate other substances through contact migration.
(9) Environmental protection
The development trend of accelerators tends to be environmentally friendly and functional. In recent years, the international community has paid more and more attention to accelerators that are prone to produce harmful nitrosamines in the rubber processing process. Most of the new environmentally friendly accelerators are developed from developed countries such as Europe and the United States. In recent years, China has gradually attached importance to environmentally friendly promotion. R&D and production of additives and pre-dispersions, among which the representatives of environmentally friendly accelerators are: ZBEC, TBzTD, TIBTD, ZBPD, ZDTP, NS, TBSI, MTT, etc.
(10) Water-soluble
For the production of latex products, it is more convenient to use water-soluble accelerators, including: EZ, BZ, MZ, TMTD, M, etc.(11) Combined use of accelerators
Each accelerator has its own characteristics. In order to satisfy the good technological performance of the rubber compound in the operation process and the excellent physical and chemical properties of the vulcanizate, several kinds of accelerators can be used together to complement each other. Rubber properties are differentiated by the characteristics of accelerators - primary accelerators and secondary accelerators.
The main accelerator, also known as the first accelerator, generally adopts an acidic accelerator (called A type) or a neutral accelerator (called N type). Thiazoles and thiurams are the most common, and the scorch time sequence of thiazoles is: M<DM<MZ<sulfenamides. Thiuram-type main accelerators are only used for film products or model products with very short curing time. Dithiocarbamate main accelerators are commonly used in latex products, as well as low unsaturated rubbers such as ethylene-propylene rubber and butyl rubber.
Secondary accelerators, also known as the second accelerator or the third accelerator, generally use alkaline accelerators (called B-type), and mostly use guanidines (such as accelerators DPG, DOTG, etc.). Accelerator H is also used, which can prolong the scorch time. The amount of secondary accelerator varies with the type of main accelerator. The sulfenamide accelerator itself is a combined accelerator. At the vulcanization temperature, the accelerator M and amine compounds will be decomposed to form an AB combined system. Therefore, secondary accelerators are generally not used. Of course, according to the needs of the process, a small amount of accelerator DPG or a thiuram accelerator can also be used in combination.
(12) Cooperation
Factors such as interaction with other rubber additives and rubber raw materials should also be considered when selecting accelerators.(13) Economy
When selecting an accelerator, the difficulty of purchasing the product in the market should be considered. Uncommon accelerators or those that are difficult to be purchased should pay attention to the impact on production when used in large quantities.
Accelerators commonly found in the market also need to take into account the purchase price. The cost of using accelerators is one of the key considerations for formulation engineers.
(14) Confidentiality
It is easy to find a formula for common rubber products, but for special or technical rubber products, formula design consumes a lot of energy and financial resources. Designing a rubber formula and keeping it confidential is very important for the development of the enterprise. The confidentiality of the formula must involve the confidentiality of the selected accelerator product, which is also one of the important issues considered by the formulation engineer and even the person in charge of the company.
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