| The process that combined microcellular injection molding and in-mold decoration(MIM/IMD)can be used to mold lightweight plastic products with high apparent quality.However,the mechanical properties of polymer products are easily deteriorated due to the uneven bubble structure in the molded products.Moreover,due to the differences in polarity and interface compatibility between the decorative film and the substrate,it is easy to cause poor interface adhesion between the decorative film and the substrate,resulting in poor appearance quality of the product.In order to solve the above problems,the mechanical properties and interfacial bonding strength of MIM/IMD products are deeply studied in this paper.And the effect of molding process parameters(melt temperature of210～240 °C,mold temperature of 30～60 °C,injection speed of 60～140 mm/s,SCF concentration of 0.2～0.6%)and glass fiber content(0～30%)on bubble structure,mechanical properties and interfacial bonding strength are studied.This provides a theoretical method for optimizing the mechanical properties of products and improving the apparent quality,and meets the lightweight manufacturing requirements of plastic products with high apparent quality and high mechanical properties.The main work is as follows:(1)The MIM/IMD cell growth model was established to predict the cell structure inside the product under the condition of film coating.Numerical simulation and test were combined to carry out simulation analysis and test sample preparation according to the test scheme design.The influences of molding parameters and glass fiber(GF)content on the bubble structure,mechanical properties and interfacial bond strength of the products were analyzed by various characterization test methods.(2)In order to improve the bubble structure of MIM/IMD process,single factor control variable method was used to study the influence law of forming process parameters and GF content on the bubble structure of MIM/IMD process by numerical simulation and physical experiment.The results showed that the increase of injection rate and SCF concentration was conducive to the formation of uniform and dense bubble structure.With the increase of melt temperature and mold temperature,the bubble structure of products deteriorates due to the influence of melt viscosity.The pore structure was improved when the content of GF was 0～20%.When the content of GF is 20-30%,it is speculated that there is a threshold of GF content with improved cellular structure.When the amount of GF exceeds this threshold,the cellular structure will deteriorate.(3)In order to solve the deterioration of mechanical properties of products,based on the change of bubble structure,the influence of molding process parameters and GF content on mechanical properties of products was studied.The results showed that compared with the forming process parameters,the mechanical properties of the products enhanced by GF were significantly improved.Compared with the products without GF added by 30%GF,the tensile,bending and shear strength of the products increased by216.11%,205.58% and 100.10%,respectively.(4)In order to solve the problem of poor performance(such as laminating)caused by poor interface bonding between decorative products and substrate,the surface quality is good or bad as the interface bond strength measurement standard,further study the forming process parameters and GF content on the influence of heterogeneous interface bond strength law.The results show that the interfacial bond strength has a negative correlation with the surface quality.With the increase of melt temperature and surface quality deterioration,the interfacial bond strength increases by 128.74%.Mold temperature has little effect on surface quality and interfacial bond strength of products.With the increase of injection speed and SCF concentration,the interface bond strength decreased by 47.98%and 35.14%,respectively.With the increase of GF content,the surface quality deteriorates and the interfacial bond strength increases by 56.23%. |
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