A basic experimental study of sandwich injection molding with sequential injection

Abstract

An experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin‐core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non‐uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function).

Effects of Process Parameters on the Skin/Core Distribution in Co-Injection: Experiments and Simulations Using a Simple Geometry

“…Experimental mould filling studies of co-injection moulding have been reported by many authors [4][5][6][7][8][9][10] , showing that the main factors influencing the skin=core distribution are the amount of core and skin material, their relative viscosities, the moulding parameters and, last but not least, mould geometry. The maximum theoretical amount of core material that can be injected without breakthrough is between 65% and 75% in simple axial symmetric parts, and is much lower in more complicated geometries [2] .…”

Space–time discontinuous Galerkin finite element method for two-fluid flows

“…In the Volume of Fluid (VoF) method [25,42,50,73] a fractional volume or color function is defined to indicate the fraction of a mesh element that covers a particular type of fluid. Algorithms for volume tracking are designed to solve the equation @c=@t þ r Á ðcuÞ ¼ 0, where c denotes the color function, u the local velocity at the front, t the time and r ¼ ð@=@x 1 ; .…”

A new adaptation of mapping method to study mixing of multiphase flows in mixers with complex geometries

“…A number of methods have been used for this purpose, such as; front capturing methods (Noh & Woodward, 1976): see e.g. VOF method (Hirt & Nichols, 1981), the method of Young (Young et al, 1980), front tracking methods (Tryggvason & Unverdi, 1990;Tryggvason et al, 2001;Unverdi & Tryggvason, 1992): see e.g. marker and cell method (Aulisa et al, 2004), adaptive front tracking method (Galaktionov et al, 2000) and mapping method (Kruijt et al, 2001a).…”