Manufacture, Properties And Processing Of Long Fiber Reinforced Thermoplastics

Lightweight of automobile is one of the effective ways for energy-saving and emissions-reducing. With the development of our society, there is a big amount of vehicle consumption in China. However, lightweight of automobile is still in the status of lacking of application and technology. Long fiber reinforced thermoplastics sheet with PP matrix (LFT-PP) has advantages of light mass, high strength, easy molding and low cost. It is becoming a substitute for engineering plastics and metal material. It is the first choice of polymer composites for lightweight of automobile. In this context, this article will do some fundamental study based on the development of LFT-PP and application of technology.First of all, a simple technique of LFT-PP manufacture is proposed with LFT production line of 200 ton annually by using in-line compounding from modified single screw extruder. It was found that improved mixing screw combining of moderate spreader-plate and extrusion die with direct zero twist roving can be used to manufacture LFT-PP with better mechanical properties.In the case of free flow screw, the influences of different conditions such as variation of screw speed, mixing length, and channel depth on RTD (residence time distribution), MRT (mean residence time) and normal variance are investigated. Yeh model is applied for fitting RTD, and Percent of Plug flow reactor P, and dead volume of continuous stirred tank reactor d are two parameters. Process parameters and screw configurations are associated with fiber breakage and dispersing by P and d. Based on RTD data analysis and mixing characterizations of in-line compounding with different geometry screw of free flow screw, grooved screw, and pinned screw, the mechanism available for fiber breakage and dispersing was given with fiber shear analysis applied by the melt. It is technical fundament for further enlargement and industrialization of LFT-PP.Secondly, the influences of matrix, fiber, and the interface on LFT-PP mechanical properties are investigated. The results show adding fiber contents is key factor for increasing mechanical properties. Strength and toughness could be enhanced by fiber length addition; on the other hand, stiffness could be increased by fiber dispersion improvement. At the same time, interfacial agent PP-g-MAH would increase the strength and stiffness, whereas reduce toughness.By combining with fiber length factor and fiber dispersion factor, the consistency of tensile strength, tensile modulus and impact strength were simulated with Kelly-Tyson's model simulation, Cox mixing principle, and strength-strain relation are applied in the study respectively. It is found that experiment status and simulation status are favorable.Adding interface agent PP-g-MAH would reduce the toughness of LFT-PP; however, hybrid reinforcement and interfacial optimization can be applied for improving the toughness of LFT-PP. The study shows good balance of strength and toughness could be achieved by interface optimization of PP-g-KH570. Meanwhile, excellent integration of high strength, high stiffness and high toughness could be from hybrid composite of LFT-PP filled by Nano-CaCO3.Finally, flow molding of LFT-PP is investigated with temperature change of pre-heating and cooling process. In addition, the influences of tooling temperature and molding pressure on LFT-PP flow molding are studied. Blank design is optimized with compression molding of engine under shield and car front module, and key parameters of LFT-PP flow molding is listed, at the same time possible shortages and its resolutions of flow molding are summarized.LFT-PP fitting for engine under shields is manufactured from in-house LFT-PP production line by in-line compounding, and qualified parts is molded with process optimization. Since 2006, and total volume of LFT-PP has increased for more than 100 ton. It has good economic returns and social benefits. In addition, manufacturing capacities and molding technique are accepted by cooperative companies. It is applied for many parts on specific domestic cars.