Hydrolytic stability of polyurethane rubber timing belt
Anti-hydrolysis stabilizers are carbodiimide products, which are divided into monomers, liquid oligomers and polymers. The addition of such anti-hydrolysis stabilizers to polyester urethane rubber is to maintain the Mooney viscosity of the rubber during storage.
For polyester urethane rubber, the three anti-hydrolysis stabilizers are very useful. Because the molecular weight of carbodiimide monomer (CDI-M) is low, it can move to the surface of the material, improve the stability of polyurethane rubber or polyurethane masterbatch, and extend their storage time. Liquid hydrolysis stabilizers, such as carbodiimide oligomers (CDI-O), are soluble in polyester polyols, therefore, it can directly add liquid anti-hydrolysis stabilizers to polyester polyols before polymerization Thereby improving production efficiency. The polymer anti-hydrolysis stabilizer has a higher content of carbodiimide, which can inhibit hydrolysis for a longer period of time.
Water molecules attack the carbonyl group of the polyester, causing it to split into an alcohol and an acid, and these products will then react with the polyester junction to further degrade the polyester. In this process, the urethane rubber timing belt will gradually degrade and gradually lose its rubber properties. Molds without hydrolysis stabilizers will continue to suffer from this hydrolysis reaction. Generally speaking, such parts will gradually lose their hardness and eventually soften into a paste. Hydrolytic stabilizer acts like a scavenger that reacts with water and acid, generating stable urea derivatives