Research On The Toughening Modification Of ABS/PMMA Blends By EMA Co-polymer

With the development of the shell material into thin-walled, light mass and attractive appearance, injection molded plastic parts with high surface luminosity and bright color is increasingly favored by consumers. Researches on the specular resin can avoid the adverse effect caused by the traditional spraying and polishing highlights process on the environment, cost, resources and manpower, and hence become a research hotspot. ABS/PMMA blends has the outstanding comprehensive performance advantages in the forming of shell products, and its surface properties can be improved effectively with the increase in PMMA content, which provides a good way for the development of specular materials. However, ABS/PMMA blends with high PMMA content have certain limitation, the weakness of toughness. The limitation used to be overcome by blending toughening modification, but there are published limited researches about modification of ABS/PMMA blends at home and abroad. Therefore, further studies on the toughening modification and its toughening mechanism has positive significance.The "zero defects" injection molding of tests specimens was explored by controlling the mould structure and injection molding process parameters in the process of die trial. The same-side runner and the whole piece of ejection mechanism overcame cold material mark and ejection mark defects, respectively. The sample quality was closely associated with molding processes such as temperature, time and pressure. Moreover, hot runner mold were more suitable for molding dumbbell tensile specimens compared to the ordinary mould, and could improve the shrinkage, cold flow marks and other injection molding defects effectively at the same time.EMA copolymer toughened ABSPMMA were prepared in a co-rotating twin-screw extruder. The effect of EMA on mechanical properties and surface gloss of ABS/PMMA blends was investigated by melt blending. Experiment results show that the elongation at break and impact strength of ABS/PMMA were improved effectively with the incorporation of EMA. Fracture morphology of ABS/PMMA blends toughened by EMA revealed that the shear yield and crazing would be induced under the action of external force, and then a large amount of energy would be dissipated in the process of inducement and the formation of yield zone. In addition, the surface gloss appeared the first after rising downward trend with the increase in EMA content, which might be related to the compatibility role of EMA. ABS/PMMA/EMA blends present optimum mechanical and luster properties when the content of EMA is6wt%.Further studies on the notch sensitivity of ABS/PMMA/EMA blends were conducted based on the formal results. The blends showed strong notch sensitivity due to the EMA component but the EMA content seemed not a factor responsible for it. Fracture morphology of ABS/PMMA/EMA blends revealed that EMA particles could have promoted the cracks near the notch tip so that the brittle fracture occurred and high notch sensitivity would be obtained in a sharper condition. Moreover, the effect of notch depth on the notch sensitivity of ABS/PMMA/EMA blends was investigated by notch tension test under low strain rate. The influence of notch depth on notch sensitivity is obvious, which might be related to the skin-core structure of injecting molded parts. It could also be obtained that there existed obvious shear yield zone while in the skin.Modifiers like SEBS-g-MAH and ABS HRP were blended with ABS/PMMA/EMA blends trying to overcome its notch sensitivity in this paper. It was found that both SEBS-g-MAH and ABS HRP could perfect the notch sensitivity of the blends. Besides, SEBS-g-MAH was more suitable for acute cases, and the modification was involved into the content ratio of SEBS-g-MAH/EMA. A better impact toughness and a worse surface gloss would be gained when the ratio turned larger. However, the modification effect of ABS HRP was independent of its content and the notch radius. Compared to SEBS-g-MAH, ABS HRP could improve the impact toughness as well as maintain the surface gloss of the blends...