Experimental On External Gas-Assisted Injection Molding Of Crystallized Products

External gas-assisted injection molding(EGAIM)can effectively improve the sink mark,which has been widely applied to the ribbed amorphous products.The crystallization of crystalline materials will lead to a large shrinkage rate of the materials,and the sink mark will produce easily in non ribbed side of products.Therefore,apply EGAIM to crystalline products is significance.Can EGAIM effectively improved the sink mark of crystallized products studied in this paper.Based on study,characteristics of crystalline materials will combine with the EGAIM process characteristics,the rule of improving product sink marks by EGAIM process parameters was studied.Meanwhile,based on the quantitative analysis of the charr area of products,the influence of EGAIM on the charr of crystalline products is discussed.Finally,the process mapping and optimization are studied,which can be used for the process guidance of EGAIM in crystalline products.This paper includes the following four aspects:(1)The effect of EGAIM on improving the sink mark of ribbed crystallized products was studied.The conventional injection molding and EGAIM were used to prepare the crystallized products,and the digital micrometer was used to measure the sink mark depth of comparative analysis.The measure results show that EGAIM can improve the sink mark depth of crystallized products of 0.365 mm to 0.085 mm,which is difficult to be distinguished by eyes;(2)The rule of improving the sink mark of crystallized products by EGAIM was analyzed.Full factor experiment was used to design the experiment scheme,and the injection products of crystalline and amorphous polymers with different process conditions were prepared.The platform was built to measure the width and depth of the products sink mark,in order to quantitatively analyze the quality of sink mark,and the influence of EGAIM process of the product sink mark is analyzed.Meanwhile,the difference between the improvement in sink mark of crystallized products and amorphous products by EGAIM is compared and analyzed.EGAIM on the improvement of sink mark in crystallized products was better than amorphous products,and the weight can be used as a secondary index for the improvement in sink mark;(3)The charr behavior of EGAIM products of injection molding was analyzed.The image processing method is used to segment the charr area of the products,and the size of the charr area is obtained to quantify the degree of charr.PP and PC products were prepared by EGAIM,and the influence of EGAIM processed on the charr of products were analyzed.Meanwhile,the charr situation of crystalline products and amorphous products was compared and analyzed,and the rule for the proportion of charr area and the process parameters of EGAIM was analyzed.The results showed that EGAIM had inproved on the charr of crystalline products;(4)The sink mark,charr and weight of crystallized products as the quality characteristics,the mapping model of process parameters is established,and the multiobjective process parameters are optimized.The process mapping model of crystallized products of EGAIM was established by uniform experimental design and stepwise regression.The process mapping model was optimized by NSGA?,and the EGAIM process parameters of the products of the best comprehensive quality were obtained.The experimental study on the process of EGAIM crystalline products provides a foundation of the successful application of EGAIM in crystalline products,and also makes a new development for the development of EGAIM.