Rubber Chem Encyclopedia

The difference between hydrophilic filler and hydrophobic filler in rubber products

Create Date:2018-07-23 10:34:46Click volume:368
The difference between hydrophilic filler and hydrophobic filler in rubber products

The rubber filler is the material filled in the rubber compound, which can reduce the cost of the rubber compound and improve the performance of the rubber product. According to the chemical composition, it can be divided into an organic filler and an inorganic filler, and can be classified into a reinforcing filler and a non-reinforcing filler according to the reinforcing property. This is well known; in addition, the rubber filler can be divided into a hydrophilic filler and a hydrophobic filler according to the hydrophilicity, and the hydrophilic property of the filler directly affects its dispersibility in the rubber, so which fillers are hydrophilic. What are the fillers and which fillers are hydrophobic fillers? How do you deal with the hydrophilicity of rubber fillers and maximize their value?

Generally, molecules with polar groups have a greater affinity for water, can attract water or are easily soluble in water, and the largest amount of rubber filler in rubber products - light calcium is a hydrophilic filler containing polar groups. Light calcium and rubber will produce negative charge when mixed, and the same sex will repel, which makes it difficult to disperse light calcium in rubber quickly. Magnesium oxide, zinc oxide, calcium sulfate and other salt fillers all contain polar groups; clay and mica powder Although inorganic fillers such as talc and kaolin contain polar groups and are not easily infiltrated by rubber, these fillers have a large particle size and a low degree of structure, so that they can be dispersed in rubber at a relatively high speed. White carbon black is a reinforcing filler commonly used in the production of light-colored rubber products. It has small particle size, high structure, low density, easy to generate static electricity, and is difficult to mix into rubber.

Hydrophobicity refers to the physical property of water and water repelling each other. Hydrophobic molecules usually converge in water. The reinforcing fillers commonly used in carbon black rubber products are also the most typical hydrophobic fillers, which are easily infiltrated by rubber. It can be uniformly dispersed in the rubber, and in this respect, it can be filled in a large amount in the rubber; however, the carbon black has a small particle size, a high degree of structure, and high heat of kneading, and thus is not suitable for high filling. Filling the rubber product with carbon black as a filler can select a product having a low structural structure and a large particle size to appropriately increase the filling amount.

In the production of rubber products, the hydrophobic filler is more easily dispersed in the rubber compound, but the hydrophilic filler is indispensable, how to improve the dispersion of the hydrophilic filler in the rubber product? Surface modification is the most effective method. Surface modification refers to imparting new properties to the surface, such as hydrophilicity, antistatic property, dyeability and biocompatibility, while maintaining the original properties of the filler. Taking white carbon black as an example, it is possible to use a high polymer or a resin to improve the surface modification, or to use a functional group in the organic molecule to chemically react with the surface of the filler to perform surface modification of the particle, and to add an appropriate amount of silane to the rubber product formulation. The coupling agent or SA improves the dispersibility of the silica in the compound and exerts better reinforcing properties.