Application of Ahmad-Rolfes-Stepto theory to the analysis of gel points in aliphatic- and aromatic-based poly(ether-urethane) networks
✍ Scribed by Stanford, John L.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 336 KB
- Volume
- 44
- Category
- Article
- ISSN
- 0959-8103
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✦ Synopsis
The signiÐcant contributions of Stepto to the development and understanding of gelation in non-linear random polymerizations are brieÑy reviewed. As an example, the recent AhmadÈRolfesÈStepto theory is used to interpret experimental gel points in stoichiometric polyurethane network-forming systems based on hexamethylene diisocyanate and 4,4@-diphenylmethane diisocyanate reacting with polyoxypropylene triols. The results conÐrm more exactly the dependence of intramolecular reaction on dilution, reactant structure and molar mass. SigniÐcantly less intramolecular reaction occurs in the aromatic-based system because of the presence of sti †er network-forming chains. Values of the e †ective bond lengths are consistent with reactant structure and show excellent correlation with those expected from solution properties. A comparative analysis of the reaction kinetics of the aliphatic-and aromatic-based polymerizations is also presented.