Studies of the Structure of Polyurethane Elastomers. II. The Determination of the Blockiness of Poly(Ether)Urethane Elastomes

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Two types of poly(ether)urethane elastomers (PEUE), which had the same composition ratio but different degrees of blockiness, were synthesized by the reaction of 4,4′-diphenyl methane diisocyanate (MDI), polyoxytetramethylene glycol (PTG), and hydrazine (HD) or ethylenediamine (EDA) by means of the prepolymer method. The degree of blockiness of the PEUE thus synthesized by the reaction of MDI, PTG, and HD was determined by measuring the molecular weight of a hard segment (urea segment), itself obtained by perchloric acid depolymerization. The values of the blockiness of PEUE which had been synthesized by the prepolymer method without any solvent or in a solvent by means of a prepolymer reaction were about 0.4 and 0.7 respectively. The degree of the blockiness of the PEUE prepared from MDI, PTG, and HD, as measured by the above method, corresponded to the infrared absorbance ratio of the PEUE synthesized by the reaction of MDI, PTG, and EDA at 1740 cm−1 and 1720 cm1. From these results two infrared absorbances, at 1740 cm−1 and 1720 cm−1, were assigned to the urethane linkage in a soft segment and at the end of an urea segment respectively.
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