Thermoplastic polyurethane microcellular fibers via supercritical carbon dioxide based extrusion foaming

Abstract

This study aims to develop, for the first time, thermoplastic polyurethane (TPU) microcellular composite fibers via an extrusion foaming process using supercritical CO2 as a blowing agent. Results showed that by employing organically modified montmorillonite clay nanoparticles (CloisiteTR 20A) in the matrix at an optimal concentration of about 1.0 wt%, the nucleation rate of foaming was enhanced, thus resulting in the formation of small bubbles in the extruded fibers. Cell sizes as low as several microns or even submicron and fiber diameters less than 30 μm were obtained in the present study. When processed with 0.5 wt% of a slip agent (Oleamide TR121), the extruded TPU fiber foams exhibited fewer cells near the fiber surface. Mechanical studies showed that the tensile modulus per mass based on the initial slope of the stress–strain curve remained almost the same for both unstretched and stretched fibers with or without foaming. However, the yield stress and the maximum tensile load at an equal mass basis were lower for fibers with foaming. POLYM. ENG. SCI., 53:2360–2369, 2013. © 2013 Society of Plastics Engineers

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.…”

Die opening-induced microstructure growth in extrusion foaming of thermoplastic sheets

“…The cell density (N 0 ) is defined as the approximate number of cells per cubic centimeter of foamed polymer and can be readily determined using the following wellknown equation [10]:…”

“…Numerous researchers and diverse inter-disciplinary industries have been very active in the field of extrusion foaming in the last few years, primarily because it allows them to manufacture thermoplastic foams continuously [8][9][10][11][12][13][14]. Extruded thermoplastic foams are being utilized in several distinct industrial fields such as in filters, membranes, packaging, biomedical tissue engineering, thermal insulation and sound dampening applications [15][16][17][18].…”

The effect of nanoclay on the crystallization behavior, microcellular structure, and mechanical properties of thermoplastic polyurethane nanocomposite foams

“…That was the reason why nanoclay content as high as 5 or 10% was investigated in this study. However, there are still some open issues regarding the effects of the added nanoclay on the micro cellular morphology and HS crystallization behaviors of nanocomposite foams. Therefore, a thorough investigation of the effects of nanoclay fillers on HS crystallization of TPU during the injection foaming process will help obtain the desired foam microstructure and improved physical properties (e.g., compression strength, barrier properties, etc.)…”

“…In recent years, TPU foamed products have been used in a variety of applications in daily life [5]. Several foaming methods have been used to fabricate plastic foams such as batch foaming [6], reaction foaming [7][8][9], extrusion foaming [10][11][12][13], and injection foaming [14][15][16]. The first two methods have lower production efficiencies that limit their industrial applications.…”