Accession Number : ADA293578

Title :   Morphology Studies of CHDI-Based Urethane by Synchrotron X-Ray Diffraction.

Descriptive Note : Final rept.,

Corporate Author : ARMY RESEARCH LAB WATERTOWN MA MATERIALS DIRECTORATE

Personal Author(s) : Desper, C. R. ; Byrne, Catherine A. ; Li, Yingjie ; Chu, Benjamin

PDF Url : ADA293578

Report Date : FEB 1995

Pagination or Media Count : 57

Abstract : Urethane elastomers having hard segments based on CHDI (trans-1,4-diisocyanatocyclohexane) and BD(1 ,4-butanediol) are notable for their high softening temperatures and low hysteretic heat buildup. Experimental studies as a function of temperature using both wide- and small-angle X-ray diffraction of a series of such elastomers, incorporating PTMO (poly(tetramethylene oxide)) soft segments, reveal the persistence of hard segment microdomains up to 275 deg C. These hard segment microdomains appear to be paracrystalline at ambient temperature, transforming to a glassy structure above ca. 100 deg C. That glassy hard segment structure is rigid to at least 275 deg C, conferring rubbery properties on the material. Electron density variance data obtained by SAXS indicate that there is little hard and soft segment mixing at 30 deg C for elastomers for which the molar ratio BD/PTMO is less than 2.0, with some segmental mixing indicated for higher BD/PTMO ratios. Changes in the microdomain structure with temperature are, for the most part, reversible for an elastomer with shorter hard segments corresponding to BD/PTMO = 1.5, but show marked irreversibility for one in which BD/PTMO = 3. These results are found to be consistent with models based on model compound data for the hard segment packing. jg

Descriptors :   *MORPHOLOGY, *X RAY DIFFRACTION, *ELASTOMERS, *URETHANES, *SYNCHROTRONS, TEMPERATURE, EXPERIMENTAL DATA, MODELS, POLYMERS, HIGH TEMPERATURE, ELECTRON DENSITY, RUBBER, GLASS, OXIDES, ORGANIC COMPOUNDS, PACKAGING, MIXING, METHYLENES, HEAT, HYSTERESIS, IRREVERSIBLE PROCESSES, HARDENED STRUCTURES, SOFTENING POINTS.

Subject Categories : Organic Chemistry
      Polymer Chemistry
      Elastomers and Rubber
      Particle Accelerators
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE