The present communication addresses compatibility of two synthetic rubber types,chloroprene and nitrile-butadiene ones,with a number of base oils of petroleum origin and lubricating greases produced thereof.Four base ...The present communication addresses compatibility of two synthetic rubber types,chloroprene and nitrile-butadiene ones,with a number of base oils of petroleum origin and lubricating greases produced thereof.Four base oils,including three naphthenic products with varying degrees of refining and one paraffinic product,were compared with each other in terms of their effect on the rubbers.Degenerative changes occurring in the rubbers on contact with the oils and greases were studied using accelerated ageing tests.Alterations in rubber parameters,such as hardness,weight and glass transition temperature,caused by interaction with oil were monitored.The main physicochemical mechanisms standing behind the changes observed in the rubber properties were found to be(i) migration of plasticizer from rubber into the oil phase,(ii) absorption of oil by rubber,and(iii) oxidation of rubber.An increase in glass transition temperature(Tg) of rubber aged in a base oil or grease was considered as an indirect indication that the plasticizer had migrated out of rubber;the plasticizer accumulation in the oil phase being directly confirmed by gas chromatography.In order to suppress the plasticizer migration,oil additivation with dioctyl adipate(DOA),a common plasticizer used in rubber formulations,was attempted.However,the DOA-additivated oils,while reducing plasticizer migration,were found to cause more swelling than the original oils in the case of chloroprene rubber.As an alternative,replacement of DOA by an alkylated aryl phosphate in nitrile-butadiene rubber formulations was considered,but it did not solve the problem either.The results of this study suggest conclusively that the type of rubber,the plasticizer,and the base oil are all the crucial parameters that should be considered when matching rubber with oil in real-life applications.Interaction of rubber with base oils and with greases produced thereof is largely controlled by(i) solvency of the base oils and(ii) polarity and cross-linking density of the rubber matrix.Higher temperatures accelerate ageing in all cases.展开更多
The receptance approach to periodic structure theory is applied to study the wave propagation and vibration power flow into a base-isolated multi-storey building due to horizontal harmonic ground motion.Multi-storey b...The receptance approach to periodic structure theory is applied to study the wave propagation and vibration power flow into a base-isolated multi-storey building due to horizontal harmonic ground motion.Multi-storey buildings and laminated rubber bearings have been modeled as periodic systems in this paper. Although the simplified model considered is quite simple,it is expected that it will bring forth the key differences between continuous and a single freedom systems.The results indicate that the isolation effectiveness depends on not only the number of storeys of the laminated rubber bearings but also the frequency characteristics of the superstructure.展开更多
文摘The present communication addresses compatibility of two synthetic rubber types,chloroprene and nitrile-butadiene ones,with a number of base oils of petroleum origin and lubricating greases produced thereof.Four base oils,including three naphthenic products with varying degrees of refining and one paraffinic product,were compared with each other in terms of their effect on the rubbers.Degenerative changes occurring in the rubbers on contact with the oils and greases were studied using accelerated ageing tests.Alterations in rubber parameters,such as hardness,weight and glass transition temperature,caused by interaction with oil were monitored.The main physicochemical mechanisms standing behind the changes observed in the rubber properties were found to be(i) migration of plasticizer from rubber into the oil phase,(ii) absorption of oil by rubber,and(iii) oxidation of rubber.An increase in glass transition temperature(Tg) of rubber aged in a base oil or grease was considered as an indirect indication that the plasticizer had migrated out of rubber;the plasticizer accumulation in the oil phase being directly confirmed by gas chromatography.In order to suppress the plasticizer migration,oil additivation with dioctyl adipate(DOA),a common plasticizer used in rubber formulations,was attempted.However,the DOA-additivated oils,while reducing plasticizer migration,were found to cause more swelling than the original oils in the case of chloroprene rubber.As an alternative,replacement of DOA by an alkylated aryl phosphate in nitrile-butadiene rubber formulations was considered,but it did not solve the problem either.The results of this study suggest conclusively that the type of rubber,the plasticizer,and the base oil are all the crucial parameters that should be considered when matching rubber with oil in real-life applications.Interaction of rubber with base oils and with greases produced thereof is largely controlled by(i) solvency of the base oils and(ii) polarity and cross-linking density of the rubber matrix.Higher temperatures accelerate ageing in all cases.
文摘The receptance approach to periodic structure theory is applied to study the wave propagation and vibration power flow into a base-isolated multi-storey building due to horizontal harmonic ground motion.Multi-storey buildings and laminated rubber bearings have been modeled as periodic systems in this paper. Although the simplified model considered is quite simple,it is expected that it will bring forth the key differences between continuous and a single freedom systems.The results indicate that the isolation effectiveness depends on not only the number of storeys of the laminated rubber bearings but also the frequency characteristics of the superstructure.
