FIELD: chemistry.
SUBSTANCE: invention relates to polyurethane flexural stiffeners designed to give local stiffness to the device near the point of attachment to the support. The flexural stiffener comprises a flexible polymer sleeve with an axial through hole for receiving an elongated flexible component and means for attaching the sleeve to the support. At least a part of the flexible polymeric sleeve is a polyurethane elastomer obtained in the reaction of an isocyanate-terminated prepolymer and a curing agent with isocyanate index of from 90 to 120. The isocyanate-terminated prepolymer contains 7 - 15 wt % of isocyanate and is the reaction product of at least one aromatic polyisocyanate and at least one polyether polyol having a hydroxyl equivalent of from 350 to 2000 and a nominal functionality of 2 - 2.3. The curing agent is one or more diol chain extenders having equivalent weight per group reacting with an isocyanate (up to 125) or a mixture of one or more diol chain extenders and one or more polyether polyols having a hydroxyl equivalent of 350 - 2000 and a nominal functionality of 2 - 2.3. The content of the hard segment of the polyurethane elastomer is from 40 to 60 wt %.
EFFECT: invention has great fatigue resistance and works well in a wide range of usage temperatures.
12 cl, 2 dwg, 3 tbl, 5 ex
