Knowledge of softeners and plasticizers used in rubber industry

1. Softener for rubber industry

Generally, it refers to aliphatic hydrocarbon oil, naphthenic oil, aromatic hydrocarbon oil, engine oil, white oil, etc., which have no functional group structure. Under mechanical and thermal action, they only lubricate, diffuse, swell, loosen and move the whole rubber molecule. If the plasticizer theory is used to explain, the softener only acts as an extramolecular plasticizer or a physical plasticizer.

2. Plasticizer for rubber industry

It usually refers to fatty acid, saturated or unsaturated fatty acid ester or zinc soap, magnesium soap, calcium soap, etc. Both contain polar groups, and through its polar force action, the polar chain end of the rubber molecular chain is encapsulated, or the polar force of the side chain end of the rubber molecule is changed, so that the rubber molecule is stabilized, which plays a role in reducing the interaction of the rubber molecular chain, improving the mutual mobility of the molecules, and ultimately improving the fluidity of the rubber compound. This chemical action of polar group to improve the plasticity of elastomer is often called intramolecular plasticization. For fatty acids or other esters and soaps, in addition to internal plasticization, because the fatty acid groups of macromolecules have good compatibility with rubber, they also have physical or external plasticization.

The selection principle of rubber plasticizer: an ideal rubber plasticizer should have the following conditions: a. good compatibility with rubber and other raw materials; B. The physical properties of vulcanized rubber or thermoplastic elastomer and other products are particularly adversely affected; C. Low volatility during oil filling and processing; D. It shall have good emulsification performance in the production of oil-extended rubber synthesized by emulsion polymerization process; E. The raw rubber shall have good processability, operability and lubricity during mixing; F. Environmental protection and pollution-free; G. Good light and thermal stability; H. Stable quality, sufficient sources and moderate price. Of course, there is no perfect ideal rubber plasticizer: rubber plasticizer manufacturers usually select raw materials according to the requirements of users, focus on solving the main performance indicators that users care about, and also provide a series of products for users to choose. Raw rubber, additives, rubber compounding and processing together constitute the production process of rubber and its products. As the plasticizing system of rubber, rubber plasticizer is more and more widely used in the process of rubber compounding and processing. It is the third largest material in the rubber industry after raw rubber and carbon black.

The key characteristics of rubber plasticizers are their compatibility and stability with rubber. Relatively speaking, the advantages and disadvantages of the three types of rubber plasticizers are as follows.

1. Paraffin-based rubber plasticizer has good oxidation resistance and light stability, but its compatibility and low temperature resistance are relatively poor. Therefore, in many applications, paraffin-based rubber plasticizer cannot provide good processing performance due to its poor compatibility with rubber.

2. Aromatic rubber plasticizer has the best compatibility with rubber, and the rubber products produced have high strength, large number of people can be added, and low price; However, the color is dark, the pollution is large, and the toxicity is large. With the increasing requirements of environmental protection, the use is gradually restricted.

3. The naphthenic rubber plasticizer has the characteristics of both paraffin-based and aromatic groups. It has good compatibility, non-polluting and non-toxic. It is suitable for many kinds of rubber and widely used. It is the most ideal rubber plasticizer. Generally, aromatic rubber plasticizers are mainly used in the production of rubber products such as SBR, BR, NR and CR, following the principle of material similarity and compatibility; Paraffin-based rubber plasticizers are mainly used in the production of rubber products such as EPDM, IIR and IR; Naphthenic rubber plasticizers are mainly used in the production of thermoplastic elastomers and rubber products such as SBR, BR and NR, and also widely used in the production of rubber products such as IIR, IR and EPDM.

If processing rubber products related to daily necessities, the toxicity of rubber plasticizer is the key indicator, so it is recommended to use high-quality environment-friendly rubber plasticizer, while aromatic rubber plasticizer is currently recognized as a carcinogen in the world, so it cannot be used. However, considering the comprehensive cost, aromatic rubber plasticizers are still widely used in places with low health requirements, such as the production of rubber products such as tires, but special attention should be paid to the labor protection of workers in the production process.

The type and specific viscosity grade of rubber plasticizer selected are mainly determined by the raw materials, production process and production cost used by users.

Paraffin-based rubber plasticizer has the worst compatibility with rubber and is difficult to process, but has good stability, elasticity and tensile strength; Aromatic rubber plasticizer has the best compatibility with rubber, easy processing, but the worst stability and toxicity; Naphthenic rubber plasticizer is between the two and is an ideal rubber plasticizer.