The effect of soft-segment structure on the properties of novel thermoplastic polyurethane elastomers based on an unconventional chain extender

Thermoplastic polyurethane elastomers (TPUs) are now widely used because of their excellent properties that include high tensile and tear strength, and good abrasion, impact and chemical resistance. TPUs are multiblock copolymers with alternating sequences of hard segments composed of diisocyanates and simple diols (chain extenders) and soft segments formed by polymer diols. Commonly used hard segments for TPUs are derived from 4,4'-diphenylmethane diisocyanate (MDI) and aliphatic diols. The aim of our research was to examine the possibility of obtaining TPUs with good tensile properties and thermal stability by using an unconventional aliphatic-aromatic chain extender, containing sulfide linkages. Three series of novel TPUs were synthesized by melt polymerization from poly(oxytetramethylene) diol, poly(e-caprolactone) diol or poly(hexane-1,6-diyl carbonate) diol of number-average molecular weight of 2000 g mol-1 as soft segments, MDI and 3,3'[methylenebis(1,4-phenylenemethylenethio)] dipropan-1-ol as a chain extender. The structure and basic properties of the polymers were examined using Fourier transfer infrared spectroscopy, X-ray diffraction, atomic force microscopy, differential scanning calorimetry, thermogravimetric analysis, Shore hardness and tensile tests. It is possible to synthesize TPUs from the aliphatic-aromatic chain extender with good tensile properties (strength up to 42.6 MPa and elongation at break up to 750%) and thermal stability. Because the structure of the newly obtained TPUs incorporates sulfur atoms, the TPUs can exhibit improved antibacterial activity and adhesive properties. (C) 2011 Society of Chemical Industry