Polyurethane elastomers : manufacture, applications, markets, and trends
Of the nearly 400 billion pounds of plastic produced every year, about 6% of that total is polyurethane (PU) and about 15% of that 6% is used purely for elastomer applications (Fig. 9.1). PU elastomers are very high performing within the general class of synthetic materials, and their applications run the gamut from footwear, to automotive body panels, truck bed liners, roller blade wheels, polishing pads for integrated circuit production, gaskets, blood bags, cattle ear tags, and polymer films. They are particularly specified when abrasion resistance, tensile strength, dynamic properties (periodic stress/strain), and low-temperature properties are paramount. They are usually not selected for applications where price is overriding, where routine temperature service greater than 120 °C is required, or where resistance to particular solvents is expected.
The PU elastomer business is divided into thermosetting elastomers that are cross-linked and made by casting techniques, thermoplastic that are made by reactive extrusion techniques, and elastomeric fibers that are made via numerous methods but generally spun from concentrated solutions. The fiber markets are handled separately since the applications are quite divergent from the other elastomers produced. Of thermosetting and thermoplastic PU (TPU) elastomers, the approximate ratio for their production and consumption is about 3:1 (Fig. 9.2) . Apart from fibers, the large producers of PU building blocks are significant participants in the PU elastomer business, most of them having a global presence in this market. However, there are numerous (thousands) of much smaller participants in the PU market that have niche product or regional presence and can compete quite effectively within specific
FIGURE 9.1 Approximate volume relationships between polyurethane elastomers and all polyurethanes consumed.
FIGURE 9.2 Approximate volume relationships between polyurethane thermosetting elastomers and thermoplastic polyurethanes consumed.
segments. Further, what concentration does exist within the PU elastomer business may in the future be prone to dilution since commoditization of products makes them less attractive to large publically held manufacturers.