【作者】 吴正环；

【导师】 瞿金平；

【作者基本信息】 华南理工大学 ， 材料加工工程， 2013， 博士

【摘要】 高分子材料共混改性是材料加工领域经久不衰的课题。在研究与开发新型高性能聚合物合金的同时，也需要协调资源，环境与能源之间的关系，实现聚合物产业的真正的可持续发展。探索高效循环利用聚合物的途径是近年来的一个重要的发展趋势。对于多组分不相容聚合物共混物来说，较弱的相容性会极大地限制其应用范围。其中一种值得关注的方法是在其成型过程中，通过加工参数的调控，进而改变物理场，从而最大程度地提升组分间的相容性，最终简便，高效，环保地实现聚合物合金的高性能化。常规塑料混炼改性普遍采用螺杆机械，主要受到剪切力场支配，不同组分的熔体只能在层与层之间进行分散，对共混体系的相容性提高有限。而新型的体积拉伸流变技术的出现，实现了塑料加工过程由剪切力场支配到拉伸形变支配的重大转变。从而使得聚合物的共混体系在熔融塑化过程中能够突破层与层之间的界限，能够更有效的发生链段的空间扩散及渗透，并且改善了分散相熔体液滴的破碎效果以及相界面的结合能力，实现多组分聚合物之间相容性的提升。基于文献调研，在选定双转子拉伸流变挤出机为加工设备，以聚苯乙烯（PS）和线性低密度聚乙烯（LLDPE）为研究对象前提下，提出以下几种方案：改变PS和LLDPE的组分；更改双转子拉伸流变挤出机的转速；变换物料在双转子拉伸流变挤出机中的停留时间；改换双轴拉伸流变挤出设备的加工温度；在PS/LLDPE共混加工过程中添加不等量的相容剂SEBS等。对PS/LLDPE共混物的微观形貌，力学性能，热性能，以及结晶性能，相容性进行了系统的研究，最终结果表明，“加工参数-微观形态-热、力学性能-相容性”之间存在密切关系。通过加工参数的调控，并且通过加工参数的调控，最终实现了体积拉伸流场中PS/LLDPE不相容共混物的强制增容。研究发现，通过双转子拉伸流变挤出机加工后，不同配比的PS/LLDPE两相共混物除了存在“海-岛”结构，还出现了独特的“蜂-巢”结构，不同组分的“蜂-巢”结构形状不同，而此结构在PS和LLDPE两相配比为20和80时最为稳定，这种结构能够在一定程度上提升两相不相容结构的稳定性。可以通过提高转速至不超过30Hz，或者转速在10-15Hz下延长停留时间，控制加工温度在180oC，以及添加相容剂SEBS的方式来完善该结构，从而提升体系的力学性能和相容性。结果显示，PS的Tg值随着自身含量减少从纯料的93.4oC降至86.0oC；转速为26Hz时的LLDPE的Tg值要高于13Hz下的Tg值13.7oC；10Hz时，停留时间的增加使得共混物的弯曲强度从7.56MPa提升至8.13MPa，停留时间越长，PS的Tg值越低；180oC时PS的Tg值为76oC，LLDPE的Tg值为-30.9oC，此时体系的相容性最好；相容剂SEBS含量为20%时，体系的断裂伸长率从不含SEBS时的8.7%达到260.34%，冲击强度从4.2MPa升至52.6MPa，PS的Tg值为86.6oC，而LLDPE的Tg值为-54.4oC，相容性达到最佳。更多还原

【Abstract】 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.更多还原