The Regression Models of Ultraviolet Rays Effect on Break Strain and Strain at the Ultimate Tensile Strength of Polypropylene Composite Materials

Many types of polymer materials used in engineering are exposed to ultraviolet (UV) light, including automotive components (car bodies, bumpers, dashboards, etc.) which will cause degradation. Some polymers are used in the form of pure polymers and some in the form of composite materials. This study aims to determine the occurrence of degradation in composite materials. This study used polypropylene as a matrix in the composite material sample, while oil palm fiber was used as a reinforcement. This research investigates the degradation of composite materials due to exposure to ultraviolet light. In this research, the degradation of the specimen samples was measured based on changes in Break Strain (BS) and Strain at the Ultimate Tensile Strength (SUTS), related to the length of UV exposure based on 6 different levels of UV exposure, i.e.: 0 hours (UV unexposed), 96 hours, 336 hours, 504 hours, 1008 hours, and 1512 hours. Then the test resulted data was used to generate a strain regression model of BS and SUTS it was obtain from this reaserch that regression model of SUTS is : Y 1 = -3.10 -9 x 3 + 7.10 -6 x 2 - 0.0067x + 14.706 with R² = 0.9894 and regression model of BS is : Y 2 = 10 -8 x 3 + 2.10 -5 x 2 - 0.0161x + 50.287 with R² = 0.9961. Furthermore, these regression models can be used to predict the maximum strain, of composite materials exposed to UV light for some many time length, which can later be used, to determine the lifetime of the material.