Study On The Processing Parameters On Mechanical Properties Of Microcellular Injection Molded Parts

Microcellular injection molded parts, which are usually sandwitch structure with solid-skin layer and inner bubble size of 5～50μm, can improve impact strength,reduce products weight and reduce less tensile strength. Meanwhile, microcelluar injection processing with less injection pressure compared with conventional injection molding, costs less energy sources, and is widely used in engineering structure parts. Because of mixing injection molding and supercritical fluid controlling in the process, microcellular injection mlding is with a narrow processing window and more complexity than traditional injection molding. Therefore, it is hard to control the precessing quality. To ensure the stability and repeatability of producing quality, appropriate process parameters is one of the key points.The influence of process parameters on mechanism performance of microcellular plastic was researched by orthogonal test in the study. The difference of weight and performance between microcellular injtection molded parts and solid parts (traditional injedtion molded parts) was compared firstly. Then the influence of each parameter on mechanism performance of corresponding molding product was ordered, and the difference of process parameters between the two processing methods was discussed. The main job was done as follows.1. PC (GE-HF1130), microcellular injection molding machine(Arburg, Germen) with special design injection units, and supercritical gas generator (N2) were used for injection molding experiments;2.The weight of products was measured on the electronic balance (AY120/AY220). It was found that the weight of Microcellular products can be reduced by 25% at the most, and 6% at least, with an average decrease of 13%, compared to the traditional molding products3.The relationship between mechanical properties and microcellular injection molding process parameters was invesitgated using DOE (Design of Experiment) L18 orthogonal table. Microcellular injection-molded parts at given procesisng conditions were cut into standard samples on versatile sampling machine according to GB/T16421-1996,GB/T12460-1996, and the smpales mechanical properties of tensile strength, elastic modulus, and impact strength were measured via microcomputer controled electronic universal testing machine and cantilever beam impact tester refering respectively. From the experimetal results, it was found that notched izod impact strength of foamed PC is 2.54 times of that of solid injection-molded parts, while the foamed parts of tensile strength and elastic modulus reduced to 83% and 90% of that of traditional injection PC products respectively. The variation of processing conditons could brought the change of tesile and impact properties, the maximum percentage was about 22.5 % and 18.8% respectively.4. Based on the orthogonal, For microcellular injection-molded parts of impact strength, the effect of sorting is mold temperature, injection speed, SCF weight ratio, melt temperature, back pressure and pre-plasticating volume were considered. For tensile strength the size of the effect of sorting is SCF weight ratio, melt temperature, injection speed, back pressure, pre-plasticating volume were considered and mold temperature. For traditional plastic of impact strength, The size of the effect of sorting is holding pressure, mold temperature, cooling time, melt temperature, injection speed and injection pressure,For tensile strength the size of the effect of sorting is cooling time, mold temperature, injection pressure,holding pressure, injection speed and melt temperature.