The Study Of Extrudate Distortion And Mechanisms Of Solution Polymerized Styrene-butadiene Rubber

The subject was supported by The National Natural Science Funds. In this work,extrusion rheological properties of two kinds of SSBR rubber and compound werestudied by a double-capillary rheometer. The headstream of extrusion distortion wasanalyzed and the effect of carbon black on rheological properties was investigated.The results showed that the overall distortion occurred when SSBR rubber wasextruded, compared to SSBR-T2003, the extrusion distortion of SSBR-2305was worse.The headstream was the instability of elongational flow at the die entrance at highshear rate. SSBR-2305had a higher viscosity, showed stronger non-Newtonianbehavior and had larger elastic energy storage, which was related to its highermoiecular weight and tin coupled structure. Raw rubber was plasticated by Hakketorque rheometer, but plastication had a small effect on the viscoelastic and extrusionproperty.The compound had a better extrusion property. Filled with large carbon blackcontent, only occurred surface distortion of different degrees. The second smoothextrusion zone occurred at high shear speed when the SSBR-2305compound filledwith30phr and50phr carbon black was extruded. Adding carbon black not onlystablilized the elongation flow and refrained from the overall distortion, but alsoalleviated the tensile deformation at the die wall and improved the surface distortion.With the increasing of the carbon black content, the viscosity of the compoundincreased, however the die swell ratio became smaller, which showed the elasticenergy storage decreased. The flow curve of the SSBR-2305compound fractured and the curve gradient was discontinuity at back and forth of the fracture, it indicated theinterfacial interaction between compound and pipe wall was strong and the stick-sliptransition could occur at high rate.The extrusion property had a bad temperaturesensitivity.The compound had less elastic energy storge and larger viscous loss at dieentrance, elongation flow tended to stable.The headstream of the compound located atdie wall, which was the interfacial instability caused by the strong stress concentration.The network formed when carbon black content exceeded30phr and Payne effectoccurred.The more carbon black content, the larger network content, Payne effect wasstronger. The elastic energy storge of compound was reduced, which was one reason ofthe improvement of the extrusion stability.The forming of the carbon network made the SSBR-T2003compound filled with20phr CB increase suddenly，while the G′and G″of the SSBR-2305compoundgradually increased. The carbon network made the die swell ratio and elastic decreaseby a large margin, the extrudate appearance was improved.The compound filled with N660had a larger die swell ratio and elastic energystorage, so the extrusion distortion was worse. Shear viscosity changed a little in theoverall rate and the compound had a weaker Payne effect. The compound filled withN375had a smaller die swell ratio and elastic energy storage. Shear viscosity wasbigger, but had a limited increase and compound had a stronger Payne effect.Thecompound filled with Z1115had a smaller die swell ratio, and the extrusion distortionwas improved observably. Shear viscosity was bigger and compound had a muchstronger Payne effect.