Elastomere Fasern auf Polyurethanbasis

Abstract

Commercially valuable elastomers can be obtained from diisocyanates and long-chain, non-polar glycols by the O. Bayer polyaddition process using crosslinking reactions. Soft elastomers of this series, in particular, are soluble in polar solvents, e.g. dimethyl formamide. Highly elastic threads can be produced from these solutions by means of the spinning process. Further development of these discoveries resulted in elastomers which are directly produced in polar solvents, and which have an essentially linear structure. In these elastomers the urea bridges Unking the soft, long-chain glycol blocks represent the actual crosslinking principle, and this by means of interaction between neighbouring CO- and NH-groups (hydrogen bonds!).
The solutions in dimethyl formamide possess valuable viscosity properties.
The elastic properties are greatly influenced by molecular weights and the build-up system (polyester, polyether) of the «soft blocks» and also by the chemical composition of the crosslinking «hard blocks».
In another development series the elastomeric state is only reached in the forming operation (e.g. during the spinning process).
The elastic properties of these new elastomeric threads are discussed in comparison with those of natural rubber. Measurement of these properties is intricate and led to the development of more delicate measuring methods. Processing techniques for spinning (wet and dry!) call for an adaptation to the great softness of these elastomers.