Development of a Hybrid Solid-Microcellular Co-injection Molding Process

Abstract

This paper presents the development of a hybrid solid-microcellular co-injection molding process that combines aesthetic and processing advantages of injection molding with benefits and property attributes of microcellular plastics (MCPs). A two-color injection molding machine has been modified and equipped with an interfacial platen and a supercritical fluid (SCF) unit for co-injection molding with regular resins and MCPs. Co-injection molded polystyrene (PS) parts with a microcellular core encapsulated by the solid skin layer have been successfully produced. Systematic experiments were carried out with solid-microcellular co-injection molding, conventional solid-solid co-injection molding, and regular microcellular injection molding processes to study the effects of process conditions and core/skin volume ratios on the penetration and morphology of the microcellular core. Light microscopy and scanning electron microscopy (SEM) of the solid-microcellular co-injection molded specimens reveal a microcellular core with fairly fine and uniform cell size of 8 to 12 microns and a cell density of up to 3 × 10 cells/cm. Under similar process conditions, microcellular cores were found to penetrate longer and generate a more uniform and thicker skin layer than do solid cores. While improving the surface finish with solid skin layers, this process is capable of producing parts with reduced sink marks, lighter part weights, and shorter cycle times.

Influence of Polylactide Modification with Blowing Agents on Selected Mechanical Properties

“…extrusion [4,11,12] and injection [1,5,6,13]. In both cases, it is important to choose the type and quantity of the dosing blowing agent, and thus the conversion of processing parameters taking into account the characteristics and max.…”

Passive mold temperature control by a hybrid filming-microcellular injection molding processing

“…Micro cells also greatly enhance the part toughness of many polymeric materials by acting as crack arrestors. Substantial research and development have been conducted on the processing and characterization of many different microcellular and filled plastics [2,[6][7][8][9][10][11][12][13][14][15]. However, the problems of microcellular surface reports and study are still insufficient.…”

Microcellular Foam Injection Molding Surface Improvement Methods

“…The final part had a solid skin and foamed core [33] . However, the production cost is very expensive.…”

“…Turng and Kharbas analyzed the penetration behavior as well [32] . A general-purpose polystyrene (GPPS) resin (BASF145D) was used as both skin and core material.…”