Formulation design of nitrile rubber

Nitrile Butadiene Rubber (NBR)
The NBR used in NBR sealants is mostly NBR 40, where 40 represents an acrylonitrile content of 40%. This type of rubber has good overall properties, including polarity, elasticity, and adhesion. Its molecular weight is usually characterized by Mooney viscosity; NBR with a Mooney viscosity of 70-80 is commonly chosen for bonding and sealing.

 

Resins
The resins compatible with NBR are mainly phenolic resins and epoxy resins, with phenolic resins being the primary component in sealants. The role of the resin in the sealant is mainly to improve the heat resistance, adhesion, stiffness, and cross-linking groups. NBR, on the other hand, mainly provides the sealant with elasticity, oil resistance, media resistance, and fatigue resistance. The two complement each other, making the NBR sealant's performance more perfect. The commonly used p-tert-butylphenol-formaldehyde resin (2402 phenolic resin) in NBR sealants is an oil-soluble phenolic resin, soluble in benzene, ethyl acetate, cyclohexane, gasoline, and vegetable oils. It has good heat resistance and aging resistance, and it has good miscibility with NBR, allowing for mixing in any proportion. While it cannot vulcanize nitrile rubber itself, it can vulcanize nitrile rubber in the presence of vulcanizing agents and accelerators.

 

Fillers and Reinforcing Agents: To reduce curing shrinkage and lower costs, various inorganic fillers can be added, such as light calcium carbonate, kaolin, and calcium silicate. Reinforcing agents are mainly carbon black and silica.

 

Solvents: Common solvents for nitrile rubber include methyl ethyl ketone (MEK), methyl isobutyl ketone (Methyl ethyl ketone), ethyl acetate, butyl acetate, and halogenated hydrocarbons.

 

Other Additives: These include antioxidants (4010NA, RD, etc.), reinforcing agents, and thickeners.