The Study On Properties Of Hnbr Compounds For Packers

Hydrogenated acrylonitrile butadiene rubber(HNBR)has very good high temperature resistance and oil resistance,duo to its saturated main chains and side acrylonitrile groups,which is widely used in the sealing field.In this paper,packer recipes were developed based on the application requirements.RPA test,high temperature tensile properties and compression tests were carried out in order to understand the reinforcing effect by high dosages of carbon black(CB).Short cut aramid fiber(AF)rather than aramid pulps were chosen for further study on reinforcements.Indeed,the modulus of these HNBR compounds with high content of carbon black filled were poved to be very high.Rubber-fiber adhesion was identified as the key for reinforcement;therefore we chose five kinds of additives to improve the adhension between fiber and rubber.The testing results showed with the increase of CB dosage,the hardness,tensile modulus and compression modulus of HNBR vulcanizates increased;RPA strain scanning showed that with increased CB content the storage modulus and the Payne effect increased.Higher peroxide dosages lead to somewhat lesser filler-filler interactions,determined from strain repeats.At 60?,there is no any effect of peroxide dosage on the storage modulus of HNBR vulcanizates,but at 150? a higher peroxide dosage led to a higher storage modulus.This is attributed to the fact that at high temperatures interactions from fillers diminished while effect from crosslink density remained.The reinforcement by high CB dosage can be visualized by a strain dependent reinforcement.Here,a higher peroxide dosage gave a lower reinforcement factor.In compression tests a strong effect of the aspect ratio of compression test sample was found.Thicker cylindric samples(L/D: give a higher compression modulus(deformation resistance).Multiple strain scannings in compression showed the existance of “Compression Payne effect”.In conclusion,80 phr of N220 was necessary for packer compounds.When adding AF the Mooney viscosity of HNBR/CB composites increased while fibers added in the form of fiber pulp did not have any effect on the Mooney values.HNBR/CB/AF vulcanizates had higher strength and hardness than HNBR/CB/pulp vulcanizates.AF and pulp showed any no effect on the glass transition temperature as to be expected,but can decrease the value of tan ?.In conclusion,AF showed a stronger reinforcement than aramid pulpWhile keeping process safety(scorch properties)the AF dramatically increased the tensile and compression modulus at low strain level;fibers have pronounced effect on shape of the stress-strain curves,both in elongation and in compression with a strong dependence on the orientation.The reinforcement is highest when fibers are orientated along the axis of deformation which is along elongation but should be oriented vertically to compression.Fibers showed a different effect on the reinforcement factors when tested in elongation and when tested in compression.With increasing stain the tensile reinforcement factor increased first,and then decreases.This is related to loss of fiber-rubber adhesion with high deformation.However,in compression the reinforcement factor increases steadily with compressive strain.A geometrical model was developed for these different behaviors.In conclusion,for packer recipes,DCF are valuable means of reinforcement with propor consideration of the deformation regimes encountered in usage.Acrylic coagent(TRIM/S),maleic anhygride grafted polybutadiene(MA),phenol-formaldehyde adhesive resin(RDL)and zinc-diacrylate(ZDMA)are all suitable to dramacially decrease the mooney viscosity of HNBR/DCF compound for easier processing except for added hydrogenated carboxylated nitrile rubber(HXNBR)which kept the Mooney viscosity stable.TRIM/S and RDL can significately improve the hardness of HNBR/AF vulcanizate.The SEM pictures showed HXNBR,MA,ZDMA and RDL all can improve the interaction between fiber and rubber.Future work can look into combining these compound ingredients.