Multiphase structure of the polyether/polyester polyurethanes and their influence on the mechanical properties

Solution cast films of segmented polyurethanes based on 4,4-diphenylmethane diisocyanate (MDI), ethylene glycol (EG) and different polytetramethylene glycol (PE)/polyethylene adipate glycol (PS) mole ratios have been investigated in terms of thermogravimetric analysis (TGA), optical microscopy (OM), differential scanning calorimetry (DSC) and stress-strain techniques. OM revealed birefringent aggregates, different in size and shape. DSC evidenced hard segments domains with short-range and crystalline internal orders. The PE/PS mole ratio influences the perfection of the short-range ordered domains, which in turn determines the tensile and hysteresis properties. Contributions to the uniaxial deformation mechanism of the rigid particules system are advanced on the basis of the DSC and OM results.