Vulcanization accelerators are referred to as accelerators for short. Adding a small amount of accelerator into the rubber compound can greatly promote the reaction between the rubber and the vulcanizing agent (crosslinking agent). A compounding agent that improves or improves the physical and mechanical properties of vulcanized rubber is called a vulcanization accelerator.

The four major functions of accelerators: one is to shorten the vulcanization time, reduce the amount of sulfur, and reduce the vulcanization temperature; the other is to improve the scorch performance of the rubber compound; Product appearance quality.

In the process of selection and use of accelerators, based on the experience of some glue friends, we have sorted out 14 items that need to be considered when choosing accelerators, and now share with you:

1. Rubber type

Different rubbers have different performance characteristics, and different vulcanization systems are used. When choosing different types of accelerators for different vulcanization systems, the matching between them should be considered.

2. Accelerator quality

Quality is one of the key considerations for formulators when choosing accelerators. In the current market, there are still many phenomena of fake and shoddy, so we must be careful when selecting them, otherwise it will directly affect the performance of rubber vulcanization or anti-aging.

3. Influence on the properties of compound rubber and vulcanizate

The accelerator participates in the formation of the rubber space network structure during vulcanization, which is directly related to the structure of the vulcanizate, that is, its physical and mechanical properties and aging properties. The accelerator has a softening effect on the rubber compound, which increases the plasticity of the rubber compound and changes the processing performance of the rubber compound.

4. Scorch performance

The accelerator has a decisive influence on the scorch time of the compound, that is, the time elapsed before the hot vulcanization of the compound begins. Therefore, the selected accelerator should make the rubber compound have a considerable scorch time, which is very important for the operation safety of the rubber compound in the process of mixing, calendering, extrusion or injection, the fluidity of the rubber compound at the initial stage of vulcanization and the adhesion to the fabric. Efforts are important. Especially in recent years, in order to improve production efficiency, the processing conditions have become more and more strict, and the requirements for the scorch resistance of the rubber compound have become higher and higher. But too long scorch time will lead to the increase of total vulcanization time, which is not only not conducive to the improvement of labor efficiency, but also adversely affects the deformation of moldless vulcanized products during the vulcanization process.

The scorch resistance of the accelerator is directly related to its critical vulcanization temperature (that is, the temperature at which the accelerator begins to act on the vulcanization process). At this temperature, the activity of the accelerator is not significant; Vulcanization. Unfortunately, this temperature has not been measured for most accelerators. When a variety of accelerators are used together, the activity of some accelerators is inhibited, and some accelerators show greater activity even below their critical temperature.

5. Vulcanization flatness

The accelerator should make the compound have a broad vulcanization flat curve during the optimum vulcanization period. In other words, the properties of the vulcanizate should not show significant changes during this period, which is especially important for thick rubber products and solid products. Rubber is a poor conductor of heat, and the surface and interior of the vulcanized compound are not uniformly heated. The broad vulcanization flatness is the guarantee to avoid over-vulcanization and to make all parts of the product vulcanized evenly.

6. Dispersion

Accelerators with poor dispersion properties in the rubber compound not only require a long mixing time, increase the power consumption of the equipment, but also often cause uneven vulcanization of the product due to uneven mixing. For some accelerators that are difficult to disperse, it can be used as a masterbatch.

7. Frosting

The frosting of the rubber compound will cause poor adhesion in the subsequent process and reduce the appearance quality of the final product, so it should be avoided. The blooming of the accelerator is related to the compatibility of the accelerator with the rubber. Generally, non-polar EPDM rubber is easy to bloom, while polar nitrile rubber and neoprene rubber are difficult to bloom. Among the accelerators, especially the accelerators TMTD and ZDMC have poor compatibility with rubber, which may cause blooming. Accelerators with large alkyl groups ZDEC and ZDBC have better compatibility with rubber than TMTD and ZDMC, and the blooming phenomenon is reduced.

8. Pollution and coloring

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. Environmentally friendly

Most of the accelerators currently used are non-toxic or minimally toxic, but some are still toxic. These accelerators cannot be used in medical and sanitary products and rubber products in contact with food. The use of toxic or more toxic accelerators should be protected during operation.

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, among which representative products are: ZDEC, ZDBC, ZMBT, TMTD, MBT, etc.

Contact information

Jason
Henan Xuannuo Chemical Co., Ltd
Email: info@hnxuannuo.com
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