The Numerical Simulation And Experimental Study On Water-assisted Co-injection Molding Of Polymer

Against the three key scientific issues of molding mechanism, interfacialinstability and front penetrating unbalanced filling flow for innovative water-assistedco-injection molding (shortened as WACIM), the systematic in-depth experimentalstudy, numerical simulation and theoretical analysis were conducted in this paper. Themechanism of interfacial instability and front penetrating unbalanced filling flowwere revealed for the first time, and the control criteria of effectively inhibiting theinterface instability and front penetrating unbalanced filling flow in water-assistedco-injection molding process was also proposed. The theoretical foundation of thewhole water-assisted co-injection molding process comprehensive controllingindustrialization science manufacture in which realist that science ensures the qualityand technology ensures success was laid. This paper mainly achieved followingresults.Against the key scientific issue of the thickness uniformity controlling interfacialinstability, the relevance theory between interfacial instability and process parametersor rheological properties was established by means of experimental study andnumerical simulation. The key control parameters of interfacial instability wereclarified, the mechanism of interfacial instability was revealed. Research results showthat the degree of interfacial instability increases with increasing of core melttemperature and die wall temperature, while decreases with increasing of watertemperature, rheological index and viscosity coefficient of core melt. Couplinginteraction between high viscosity melt cured film viscous stratification induced shearstress gradient and velocity field perturbation is a key factor which causes the coremelt and water stratification interface unstable.Against the key scientific issue of front penetrating unbalanced filling flow inbifurcated die in the WACIM process, the relevance theory between front penetratingunbalanced filling flow and process parameters or rheological properties wasestablished by means of numerical simulation. The critical control parameters of frontpenetrating unbalanced filling flow were clarified, the mechanism of front penetrating unbalanced filling flow was revealed. Research results show that the degree of frontpenetrating unbalanced filling flow increases with increasing of die wall temperaturedifference and core melt delay time, while it decreases with increasing of core-skinmelt viscosity ratio, besides, the degree of front penetrating unbalanced filling flow ofwater is significantly greater than core melt. The front penetrating unbalanced fillingflow is induced by the unbalance of front penetrating flow resistance in each branch,and it’s the theoretical premise of inhibiting unbalanced filling flow that its frontpenetrating flow resistance has self-balancing features. When core-skin melt viscosityratio is greater than1, the core melt front penetrating flow resistance has alsoself-balancing features, which makes its front penetration show balanced filling flowstate even though the presence of die wall temperature difference interference.