Development of Polyurethane Engineering Thermoplastics. 1. Preparation and Structure

PATRICIA M. FRONTINI; MARTA RINK; ANDREA PAVAN

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 1993 p. 2003 - 2022

0021-8995

Rigid, tough thermoplastic copolyurethanes were prepared by a prepolymer technique. Thesoft-segment content was varied over the 5-30 wt %. Six stoichiometric formulations basedon diphenylmethane 4,4?-diisocyanate ( MDI ) , one or two different polyetherglycols, andone or two chain extenders of different structure were examined to test the possibilities ofvarying the degree of crystallinity of the products. Despite their thermoplastic characteristics,the resulting products were insoluble in the solvents normally used for elastomeric polyurethanes.The influence of curing temperature upon crystallinity and degree of polymerizationwas analyzed. Phase-structure analysis, performed by differential scanning calorimetry,dynamic-mechanical thermal analysis, and wide-angle X-ray scattering revealed complexphase structures strongly dependent on previous thermal history. In any case, the softsegments appear to constitute a dispersed phase in a rigid amorphous or semicrystallinematrix. Some samples exhibited two hard-segment glass transitions associated with theexistence of a bimodal length hard-segment distribution. X-ray diffraction patterns suggestedthat more than one crystalline form was present in the crystalline phase