Compression Molded Polyurethane Block Copolymers. 3. Evaluation of Microphase Compositions
Abstract
This paper presents methods to estimate the microphase compositions in polyurethane segmented block copolymers based upon combined analyses by small-angle x-ray scattering and differential scanning calorimetry. The methods are applied to a system of polyurethanes prepared from 4,4'-diphenylmethane diisocyanate, 1,4-butanediol, and a 2000 MW ethylene glycol capped polypropylene oxide prepolymer. The resultant microphase compositions predict microphase transition temperatures that compare well with observed values. The versatile mechanical properties of segmented polyurethane elastomers are generally attributed to the formation of a microphase separated structure due to incompatibility of the glassy hard segment and rubbery soft segment sequences. From these results, it appears that the morphological behavior of polyurethanes is strongly dependent on polydispersity. In monodisperse model compounds, extend chains are predominant, while in normal segmented polyurethanes, the evidence supports the occurrence of some type of hard segment chain folding or reentry into the hard microdomain.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 27, 1990
- Accession Number
- ADA220160
Entities
People
- J. T. Koberstein
- L. M. Leung
Organizations
- University of Connecticut