Influence and prediction of processing parameters on the properties of microcellular injection molded thermoplastic polyurethane based on an orthogonal array test

Abstract

Thermoplastic polyurethane is a commonly used polymer in our daily lives. Microcellular injection molding (a.k.a. MuCell) is an emerging method capable of mass-producing thermoplastic polyurethane foams with tunable microstructures and properties. This study investigated the effects of four main processing parametersnamely, plasticizing temperature, carbon dioxide (CO 2 ) content, injection volume, and injection speed-on microcellular injection molded thermoplastic polyurethane ASTM tensile test bars. Property variables of interest included the cell diameter, cell density, skin layer thickness, and Young's modulus. Influence sequences of parameters on each variable were obtained via the orthogonal array test method. It was found that the CO 2 content primarily affected the cell diameter and cell density, whereas the temperature mainly influenced the skin layer thickness and Young's modulus. Surface fitting of each dependent variable was done by combining its two most influential parameters from the experiment data. The value of each property variable within the processing window could then be predicted from the fitted surface. In addition, microcellular injection molding of thermoplastic polyurethane was simulated by a commercial software package, and the simulated results confirmed the reliability of the cell diameter prediction.

Preparation of microcellular thermoplastic polyurethane (TPU) foam and its tensile property

“…Due to above‐mentioned advantages, CO 2 has been adopted as the blowing agent to acquire fiber shape, bead shape, and bar shape TPU foams . While these above noted foaming processes were mainly used to investigate the effects of processing parameter and blowing agent on the cell morphology.…”

Microcellular injection molding of polypropylene and glass fiber composites with supercritical nitrogen

“…25,26 Using microcellular injection molding technology with SCFs, the cell morphology, surface quality and mechanical properties of molded parts can be controlled by the injection molding processing parameters such as blowing gas content, shot size, injection speed, melt and mold temperature, melt pressure, dwell time and so on. [27][28][29][30][31][32] Since the properties of molded polymer composites are affected by the processing conditions and the amount of reinforcement, a finer cell structure, a more uniform cell size distribution and a better reinforcement distribution and orientation can be achieved by controlling the foaming processing conditions.…”

Morphology and properties of thin-walled microcellular polycarbonate/acrylonitrile–butadiene–styrene blend foam

“…4,5 Moreover, microcellular injection molding has the additional advantage of using environmentally friendly blowing agents, such as supercritical carbon dioxide (ScCO 2 ) or supercritical nitrogen (ScN 2 ). There are some researches about the preparation of microcellular plastics by supercritical gas, such as microcellular polystyrene, 2,6,7 polyurethane, 8 cross-linked polyethylene, 9 polypropylene, 10 polycarbonate/poly(lactic acid) blend, 11 polyurethane/polylactic acid, 12 poly(ether ether ketone) and poly(ether imide) blend 13 and polypropylene/polystyrene blend 14 by ScCO 2 . And microcellular polypropylene, 15 polyethylene terephthalate glycol, 16 poly(phenylene sulfide), 17 polystyren, 18 ABS, 19 polypropylene/high-density polyethylene, polypropylene/low-density polyethylene, and poly(lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxy-valerate) blends, 20 poly (lactic acid)/poly(ε-caprolactone) blends, 21 and acrilonitrile–butadiene–styrene (ABS) 22 foams were prepared by ScN 2 .…”