Effect Of Long Chain Branching On EPDM Processing Properties And Physical Properties

Because of saturated molecular main chain,EPDM has excellent in heat resistance,aging resistance,ozone resistance and other properties,and is widely used in automobiles,seals,wires and cables.In order to meet the high-quality and low-cost production requirements of EPDM products,it is necessary to fully understand the impact of polymer structural parameters on processing and product performance.In recent years,research has found that in addition to chemical composition,Mooney viscosity,and molecular weight distribution,long-chain branching is also an important structural parameter that affects EPDM processing properties and physical and mechanical properties.In this paper,EPDM with different long-chain branching degrees were selected as the raw material.The rheological method was used to characterize the long-chain branching.As results,RPA data indicated that long-chain branched EPDM had lower ?value and larger branching index.Rotary rheometer data showed that as the long-chain branching degree increased,the degree of deviation of G 'gradually increased,and the slope of the low-frequency end region became smaller.The v GP chart showed that as the degree of long-chain branching increased,the ? value and the area under the curve decreased,and the elasticity of the material increased.By adjusting the oil content,under the condition that the hardness of the vulcanizates were basically the same,the effects of long-chain branching on EPDM processing properties and physical and mechanical properties were studied by Mooney viscometer,rotorless vulcanizer,extruder,and Zwick electronic tensile machine.The results showed that with the increase of the filling amount,the compounds had lower Mooney viscosity,more output,lower Green strength and slower vulcanization rate,and the vulcanizates had lower tensile strength,smaller elongation at break,lower delfttear strength,and higher compression set.Compared with linear EPDM,long-chain branched EPDM compounds had lower Mooney viscosity,larger output,better processing safety,smaller Green strength and lower cross-linking degree.The vulcanizates had slightly lower tensile strength,slightly lower delft tear strength,and slightly larger compression set.When other structural parameters were similar,compared with EPDM with lower long-chain branching,EPDM compound with higher long-chain branching had lower Mooney viscosity,larger output,better processing safety,higher Green strength and higher degree of cross-linking.The vulcanizates had slightly higher tensile strength,slightly higher delft tear strength and slightly smaller compression set.In addition,for EPDM,with the content of the third monomer increased,although the compounds had higher cross-linking degree and faster vulcanization rate,at the same time the scorch time became shorter,which resulted in the worse processing safety.In addition,two related equations were constructed using the software: first,the relationship equation between the compounds Mooney viscosity and the polymer Mooney viscosity,and ??;and second,the relationship equation between the output and the compounds Mooney viscosity.This has an important guiding role in predicting the Mooney viscosity and extrusion properties of the compounds in the context of known structural parameters of the polymer EPDM in industrial production.Thermoplastic elastomer combines the advantages of rubber and plastic.It can maintain the elasticity of rubber at normal temperature,and also shows the processing fluidity of thermoplastic at high temperature.Owing to the unique physical and processing properties,thermoplastic elastomer have the advantages that rubber material does not have.The last chapter of this paper studied the effect of long-chain branching on the processing properties and physical and mechanical properties of EPDM / iPP TPV(dynamic vulcanized thermoplastic elastomer).The results showed that during dynamic vulcanization,the cross-linking density would affect the particle size of the rubber phase.Compared with linear EPDM,long-chain branched EPDM had lower molecular weight and broader molecular weight distribution.After blending with i PP,the rubber phase had lower cross-linking density and larger particle size.The TPV had poorer process flow,lower tensile strength,shorter elongation at break,larger tensile permanent deformation,and lower elasticity.Compared with lower long-chain branching degree EPDM / iPP TPV,EPDM / iPP TPV with higher long-chain branching degree had higher cross-linking density and smaller rubber phase particlesize.Correspondingly,the TPV had better processing fluidity,greater tensile strength,smaller tensile permanent deformation and higher elasticity.