Study On Condensed Structure And Aging Properties Of Glass Fiber Reinforced Polypropylene Injection Molded Parts

With the development of science and technology,glass fiber reinforced polypropylene composite products are widely used in various fields of engineering and life because of their high strength,low weight and low cost.At the same time,injection molding is one of the main molding methods for glass fiber reinforced polypropylene parts because of its ability to form complex parts,high production efficiency,flexible process parameters,and easy operation.Different injection molding processes will cause the parts to form different internal condensed structures,which will bring different mechanical properties to the parts and affect the service life of the products.The research object of this paper is a square shell part,which uses polypropylene reinforced material with 10% glass fiber content.The study is to explore the condensed structure and aging properties of glass fiber reinforced polypropylene parts due to the change of process parameters during injection molding.Firstly,the Moldflow is used on the injection molding process of the glass fiber reinforced polypropylene box-shaped shell parts to get the process window,determine the process parameters and their range of variations used in the injection molding experiments performed in this paper.Then the orientation of the glass fibers in the parts under different process parameters was simulated.The results indicate that higher melt and mold temperature,lower injection time,medium-sized holding pressure and longer dwell time facilitate the the glass fibers to orientate along the melt flow direction.Secondly,an injection molding experimental platform was build and the injection molding experiment by changing the five process parameters of melt temperature,mold temperature,injection time,holding pressure and holding time was carried out,and the parts formed under different process parameters were obtained.Then the crystallinity and the tensile section of the part were examed,the influence of process parameters on the internal condensed structure of the part was studied.The results show that higher melt temperature,mold temperature,holding pressure and time are beneficial to the formation of compact condensed structure,promote the full growth of crystal structure and improve crystallinity.Subsequently,the parts formed by different process parameters were respectively subjected to damp heat aging,natural aging and xenon lamp aging,and used tensile testing machine,X-ray diffractometer,etc.,to study the effects of different condensed structures caused by process parameter changes on the aging properties of the parts.The results show that,the tensile strength of the sample is significantly reduced after aging.The parts formed under the melt temperature of 250?,the mold temperature of 55?,the injection time of 4s,the holding pressure of 7.4MPa and the holding time of 12 s have good anti-aging properties.Finally,the surface morphology of the parts before and after aging was observed by scanning electron microscope,and the infrared spectrum test and analysis of the parts were carried out.The results show that for the parts formed under the same process parameters,the aging of the xenon lamp has the deepest effect on the aging of the parts,followed by natural aging,and damp heat aging has the least effect on the aging of the parts.This also indicates that glass fiber reinforced polypropylene parts are not suitable for use and storage in a strong ultraviolet environment,and have a long service life in a hot and humid environment.