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TPO (thermoplastic olefin) composite for rear bumper back beams was developed. In this study, the composition of PP (polypropylene), rubber and mineral fillers was optimized to minimize the intrusion and the failure after crash. The optimization of the composition was achieved using the mixture design of experiments. The physical properties of TPO composites with various compositions were investigated and the effect of each material on the crash performance of back beam was studied through CAE (computer-aided engineering). The back beams made of the optimized TPO composite for a subcompact car were prepared for the ECE 42 crash test and the TPO-based back beam showed even better performance than conventional PC/PBT-based counterpart. In addition, the newly developed composite has delivered a 15 ~ 40% cost saving and 4 ~ 10% weight reduction versus conventional PC/PBT and GMT (glass mat-reinforced thermoplastic).

Optimal Composition of Light-weight BMC (Bulk molding compound) for automotive headlamp reflector using Glass bubble was investigated. Glass bubble (G/B) normally has low heat conductivity which has a bad influence on cycle time making products like reflectors. It was very important to improve the productivity of Light-weight BMC by means of finding optimal composition of base resin, curing agent and other additives. This study focused on the ideal ratio of each component of BMC, unsaturated polyester resin, glass bubble, inorganic filler, glass fiber and additives. Mechanical and environmental properties of the product which was made of optimized light-weight BMC were evaluated to compare with the properties of the product which was made of existing BMC.

Since the environmental problems and new stricter regulations are forcing the industries to introduce more ecological materials for their products, biodegradable materials have attracted increasing attention. Among these materials, Polylactic acid (PLA) is remarkable for its modulus, strength, chemical resistance. However, PLA could not be used for automobile industries for its low heat resistance and impact strength. Therefore, in this study natural fiber was introduced as reinforcements in order to improve the properties of PLA. And for various experiments, Polypropylene (PP) was used as matrix resin instead of PLA. Especially for improving the properties of PLA composites, surface treatments, annealing, and adding rubber elements were performed. With surface treatments, we found that the mechanical properties of composite were improved. And with annealing treatment, we found the remarkable increase of heat resistance of PLA composite.

The gel fraction and the curing rate of the silver mirror protective film according to the curing condition were investigated. Two-packaged polyurethane dry film made from acryl polyol and three different isocyanate curing agents (HDI-biuret, HDI-trimer and IPDI trimer) were built on the silver mirror layer in order to protect the layer. FTIR/ATR spectra showed the isocyanate content was clearly decreased and the gel fraction was increased as curing temperature and time were increased. The optimum curing condition of the silver mirror protective film was 80□ and 30 minutes. The dry film prepared with the optimum condition satisfied all tests in our materials specification for automotive interior parts. Moreover, the pencil hardness of the film containing dibutyltin dilaurate was stronger than the film without catalyst.

In this study, for the composite polypropylene in instrument panel, mechanical and chemical properties of primer-less waterborne paint is investigated by formulations of paint composition and material properties according to process conditions are also investigated. Primer-less waterborne paint with 30% of polyolefin modified acryl emulsion, 15% of alkyl methacrylate emulsion, 3% of cross-linked polymethacrylate bead, 2% of amide modified polyethylene wax had good adhesion properties onto polypropylene substrate without adhesion promoter and showed better properties on long term reliability test. In production line test, IR curing condition was insufficient for waterborne paint due to high latent heat of evaporation and complicated feature of instrument panel. Waterborne primer-less paint was sensitive to painting environment compared with solvent-borne paint.

Physical properties of waterborne soft feel coatings for instrument panel were investigated. Soft feel coatings give warm and velvet touch for cold and hard plastic materials. A waterborne soft feel coating is composed of two parts. Part A contains polyester polyurethane dispersion (PE-PUD), OH-functional water dispersible polyurethane resin (PC-PUD) and OH-functional water dispersible alkyd resin (OH-PA). Part B contains hydrophilic hexamethylene diisocyanate trimer (HHDI). The soft feeling of a coated panel is related with the amounts of PC-PUD and OH-PA. The physical properties of coated panel are controlled by the NCO/OH ratio from Part A and Part B. The results from all reliability tests satisfied soft feeling, scratch, chemical resistance and fogging.

Physical properties of sprayed polyurethane skin for instrument panel were investigated. Optimized sprayed PU(polyurethane) composition for instrument panel was determined by reaction speed measurement, which were polyol of 6000 molecular weight and modified MDI (NCO=25%). For making sprayed PU skin, raw material was sprayed from 15 cm of distance, at 15 g/min of spraying rate, on 70°C of mold, with 75°C of raw material. Sprayed PU skin had lower density than PVC skin when investigating cross sections of skins using scanning electron microscope (SEM). But the reliability test results satisfied all the specification requirements like scratch, chemical resistance, contamination resistance and fogging. Tensile strength, hardness and elongation of sprayed PU skin were slightly changed during heat aging, but the changing rate was much smaller than those of PVC skin.