Preparation of polypropylene composites being cured their surface characteristics for automotive application and it's characterization

The surface aesthetics at interior and exterior parts of modern automotive become more important day by day. As a matter of fact, nowadays, along with the high-quality ones, it is also a characteristic looked for for middle-class vehicles, too. Polypropylene (PP) material is widely used in the manufacture of interior and exterior components in automotive industry in terms of its tribological properties fortified by line-filling and tempers as well as its being cheap, lightweight, easily handled, and recycled. In this study, polypropylene compounds were prepared in order to improve quality surface properties of automotive interior parts (dash panels, inner door panels, etc.). When preparing the compounds, melt mixing method is used in a twin screw extruder to obtain a homogeneous mixture. Physical, thermal, mechanical, morphological and tribological tests were applied to the samples taken from the compounds in order to determine their effect on the quality of the finished surface. The results show that the main factors affecting scratch resistance are the crystallization, the interaction between the polymer and the filler, the activity of the dispersion in the main matrix, hardness / impact resistance balance, and the surface modification with the slip agent. In this context, thermal, mechanical, morphological and tribological effects that cause scratch resistance in developed PP composites were examined, and surface aesthetic performance was compared. Samples were examined morphologically at 650-4000 cm-1 using fourier transform infrared spectroscopy (FT-IR). At the end of the investigations, PDMS containing silicon additive was found to have poly (dimethylsiloxane characteristic peaks). In the physical characterization of all samples, density measurement was carried out according to ISO 1183 standard. Density was measured with a D-type durameter according to the Shore D test standard. Compared to the polypropylene homopolymer, higher melt flow index (MFI) values of the polypropylene copolymer used as the matrix material were determined. Mechanical characterization was performed with test equipment. From the tensile-strain results, the elastic modulus and % tensile strength and tensile strength values were calculated. How different matrix and different proportions affect the mechanical properties of fillers and additives has been determined. All specimens were thermally characterized by DSC. Percent crystallinity values were found to be higher in talc-containing composites than fillers containing wollastonite as a filler. Heat deflection temperature test (HDT) was obtained from samples whose main matrix was polypropylene homopolymer compared to other PP types. When the amount of talk increased, the HDT value also increased. It was found that the crystallinity of composites containing wollastonite as filler using SEBS (styrene-ethylene-butylene-styrene triblock copolymer) as elastomer was higher. The test method used for the scratch tests was carried out under load of 15 N in the Erichsen 430 II P scratch tester. Using a cross hatch cutter scratch method, 20 horizontal and 20 vertical scratches were applied at a distance of 2 mm with a 90 degree angle with a scratch device. In the device, a 1 mm ISO 1518-1 type was used as the end. Scratch points (zones) were created to test the scratch widths of the test samples. In the scanning electron microscopy (SEM) analyzes of the scratch areas, images from 10 different points for each sample were taken in a size of 500 μm. Scale width averages were calculated with SEM images. The scratched resistance and scratch visibilities of the samples formed with the scratch zones were calculated. As scratch width increases, scratch protection decreases. It has been found that blends with the main matrix polypropylene copolymer, which significantly affected the scratch formation compared to the homogeneous or copolymers used, provided better scratch protection than polypropylene homopolymers. In particular, it has been found that the use of wollastonite, SEBS and silicon admixtures in these mixtures contributes significantly to the prevention of scratch formation, and, on the other hand, it has been found that mixtures containing talc filler increase scratch formation. As a result of the measured scratch visibility tests due to color change, it was determined that wollastonite added to the construct using polypropylene copolymer increased scratch appearance when used with SEBS compared to talc. Within the scope of the studies to determine the scratch characteristics from the tribological properties, the scratches on some samples were examined by SEM. These investigations were carried out in 100μm size, and damage to the samples, fish back and cut formation were detected. In the talc used, the scratch formation is cut to the last stage, while the scratch formation in the wollastonite structures remains in the second stage, the fish scale. When comparing the results of scratch visibility detected with a spectrophotometer to determine the scratch resistance and the scratch-protected results of the scratch width measurement with SEM for the same specimens, no link between the two methods was found.