Study On Forced Compatibilization And Mechanism Of Polystyrene/Linear Low Density Polyethylene Blends In Volume Elongational Flow Field

Polymer blends modification is the enduring issue in polymer processing field. In orderto achieve the truly sustainable development of polymer industry, new high-performancepolymer blends are researched and developed, meanwhile, the relationships that among re-source, environment and energy should be coordinated. It is a significant development ten-dency that exploring efficient means of recycling polymers in recent years. Referring to mul-ticomponent incompatible polymer blends, the application areas would be greatly restrictedfor its poor compatibility. There is an attractive method. Physical field is changed by control-ling processing parameters, so that the compatibility among components can be enhanced tothe maximum. In other words, the high performance of polymer blends can be achieved sim-ply, efficiently, and environmental friendly.The screw processing machine is commonly used in conventional polymer blendingmodification, which is dominated by shear force field. Molten fluid of different componentscan only be dispersed among layers, it will improve the compatibility of polymer blends lim-ited. A new volume elongation rheological technology comes out and achieves the significantchange of plastics processing procedure, which from dominated by shear force field to domi-nated by elongation force field. It makes polymer blends break the boundary among layersduring melting and plasticating process, the diffusion and penetration of chains can be ful-filled more efficiently in space, moreover, it is improved with the breaking effect of the dis-persed phase molten droplet and the combining ability on the phase boundary, the compatibil-ity among multicomponent polymers is promoted.Based on documents research, in the premise of choosing twin-rotor extruder dominatedby elongation rheology as the processing device, five experimental programs were proposed:altering the ratios of PS and LLDPE; changing the rotation speed of twin-screw extruderdominated by elongation rheology; extending the residence time of materials in thetwin-screw extruder dominated by elongation rheology; Altering the processing temperaturein the twin-screw extruder dominated by elongation rheology; and adding different ratios ofunreact compatibility agent SEBS. The micromophology, mechanical properties, thermal per-formance, and crystality properties were all researched systematically, which all reflected thecompatibility properties. Final results showed that a close relationship existed in “processingparameters-micromophology-thermal, mechanical properties-compati bility”. Elongationalflow field induced forced compatibilization on Polystyrene/Linear low-density polyethyleneimmiscible blends were finally fulfilled through controlling processing parameters. It was shown in the research that, except “sea-island” structure, a particular “bee-comb”structure existed in PS/LLDPE blends, in which different component appeared with different“bee-comb” structures, the structure was in the most steady state especially when the ratio ofPS and LLDPE was20and80. Such structure could promote the stability of the two-phaseincompatible structure in a certain degree, which could be completed through four methods,such as raising the rotation speed to not more than30Hz; extending the residence time in thecase that the rotation speed was between10to15Hz; controlling processing temperature at180oC; and adding compatibilizer SEBS, so that the mechanical properties and compatibilitycould be promoted.The results also showed that the Tgvalue of PS decreased from93.4oC to86.0oC with thecontent dropping from100%to20%; the Tgvalue of LLDPE in the rotation speed of26Hzwas13.7oC higher than that of LLDPE in the rotation speed of13Hz; the flexural strength in-creased from7.56MPa to8.13MPa with the extending of residence time when the rotationspeed was10Hz, the longer of the residence, the lower of the Tgvalue of PS; the Tgvalue ofPS was76oC, while the Tgvalue of LLDPE was-30.9oC when the processing temperaturewas180oC, the compatibility of system was the best; The elongation at break of the systemincreased from8.7%to260.34%, and the impact strength of the system increased from4.2MPa to52.6MPa with the compatibilizer SEBS content raised from0%to20%, mean-while, the Tgvalue of PS was86.6oC, and the Tgvalue of LLDPE was-54.4oC, the compati-bility of system achieved the best.