Study On The Nitrile-Butadiene Rubber Insulation Material

In this paper, the statistical results on the faults of the 9621 nitrile-butadiene insulation materials are analysized. The statistical results show that the mechanical properties of 9621 insulation are unstable, and often fluctuate in a bigger range. Its elongation rate is about 200% which is close to the lower limit of the technical specification. Its compatibility with 5-III insulation materials and Jx-6 glue is not fine, so that its bonding strength with 5-III insulation materials and Jx-6 glue is lower. These disadvantages of the 9621 nitrile-butadiene insulation materials leads to fault adhension between insulation and motor case, such as, easy to be teared, weak bonding, and lower the quality and reliability of the solid motor.Through analysing the correlation between the basic formulation of 9621 insulation and its properties, we found the reason of the instability of 9621 insulation's properties is that the asbestos (one of the ingredients in the formulation) cannot disperse uniformly in the basic material of rubber and its compatibility with the basic material is not good enough.In this paper, we found out two methods to modify the properties of the insulation. One is to replace parts of asbestos with carbon fiber. And the other is to add coupling agent as one of the ingredients to the basic formulation.The experimental results show that the addition of the carbon fiber can improve the mechanical properties and bonding property of 9621 insulation materials. When the mass ratio of the asbestos and the carbon fiber is 1:1, the properties achieve the best level. Adding coupling agent of KH550 into the basic material can also improve the properties of the insulation. When the conten KH550 of is 1%, the properties are ideal. So, the modifying study of 9621 insulation practically resolved the problems such as: the instability in its properties, lower elongation rate and weak bonding with case and propellant.