William J. Farrissey

The Effect of Microcrystalline Structures upon the Physical Properties of Polyurethanes

This article proves the existence of crystal structures in elasto meric polyurethanes and describes the changes in molecular struc ture observed to result from thermal aging. Experimental results show that annealed polymer exhibits properties which are different from quenched, amorphous polymers, evidence of formation of crystal structures during the annealing process.

Polymers from Unconventional Reactions of Isocyanates

HE RAPID GROWTH of the polyurethane industry over the past twenty years has T been adequately documented in trade journals and market reports [ l ] . The remarkable versatility of polyurethane as a class may be illustrated by the varied forms available: rigid, semi-flexible and flexible foams, microcellular elastomers, thermoplastic elastomers, coatings, spandex fibers, and integral skin cellular products, to name a few [2]. All of these products are derived from reacting a very few types of isocyanates with an almost endless variety of polyols or polyamines or water. It has been the task of the applications chemist to select from these materials, the functionality, molecular weight and structural types of reactants which, when combined, will yield the desired properties. Much has been written concerning the chemistry and structure-property relationships of the polyurethanes [2,3]. The most common fault of these otherwise versatile materials i s their relatively low upper use temperature. This report describes other polymers derived from isocyanates, which utilize the many other reaction routes open to these very reactive monomers to produce a large number of potentially useful polymers of greatly improved thermal stability. The general reactions of isocyanates are outlined in Scheme I. From these reactions may be derived the polymers to be described subsequently. Most of the reactions outlined are strongly susceptible to catalysis, as described in Table 1.

A high-impact polyurethane engineering thermoplastic

NJECTION MOLDABLE THERMOPLASTIC POLYURETHANE (TPU) ELASTO’ mers have enjoyed widespread usage in a variety of applications for nearly two decades. Generally, materials range in hardness from 70 Shore A to 80 Shore D and exhibit the excellent elastomer properties outlined in Table 1. Applications include skate wheels, fork lift wheels, ski boots, automotive parts, etc. This wide variety of properties available for TPU elastomers is derived from the composition and extent of the hard and soft segments in the polymer. A typical MDI based polyurethane elastomer consists of soft elastomeric segments of polyether or polyester polyols linked together with hard blocks of diphenylmethane diisocyanate/extender polyurethane. An example derived from poly (tetramethyleneether) glycol, 1,4-butane diol and MDI is diagrammed below: