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Incorporation of Poly(Dimethylsiloxane) into Poly(Tetramethylene Oxide) Based Polyurethanes: The Effect of Synthesis Conditions on Polymer Properties

Two procedures for incorporating low levels of poly(dimethylsiloxane) (PDMS) in polyurethane (PU) have been studied. The bulk synthesis of poly(siloxane-urethane) was performed in two steps: the first involves the formation of a prepolymer between isophorone diisocyanate (IPDI) and poly(tetramethylene oxide) (PTMO). In the second step 1,4-butanediol (BD) was added as the chain extender. A kinetic study followed by infrared spectroscopy showed the higher reactivity of PDMS compared to PTMO. Thus, two procedures for incorporating PDMS are described, depending on whether the poly(dimethylsiloxane) was introduced in the first or in the second step. Films were made from these formulations, and we studied their morphology. The products obtained from each procedure were characterized by size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMTA) and uniaxial tensile testing, and showed significant differences. These poly(siloxane-urethane) polymers are intended to be used as hydrophobic coated formulations on polyester fabrics in a further study.