Effects of crosslinking on thermal and mechanical properties of polyurethanes

• Published in: Journal of applied polymer science Vol. 83; no. 1; pp. 212 - 223
• Main Authors: Chiou, Bor-Sen, Schoen, Paul E.
• Format: Journal Article
• Language: English
• Published: New York Wiley Periodicals, Inc., A Wiley Company 03.01.2002; Wiley
• Subjects: Applied sciences; crosslink density; Exact sciences and technology; glass-transition temperature; Organic polymers; Physicochemistry of polymers; polyurethane; Properties and characterization; Rheology and viscoelasticity; Molecular structure; Dynamic mechanical properties; Crosslink density; Crosslinked polymer; Property structure relationship; Experimental study; Glass transition temperature; Etherurethane polymer
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.10056

The effects of chemical crosslinking on the thermal and dynamic mechanical properties of a polyurethane system were examined. The polyurethanes were prepared from poly(propylene glycol), a diol; trimethylolpropane propoxylate, a triol; and poly(propylene glycol), tolylene 2,4‐diisocyanate terminated, a diisocyanate monomer. The crosslink density was controlled by varying the triol concentration from 10 to 70 mol % and the isocyanate‐to‐hydroxyl (NCO/OH) ratio from 1.0 to 1.3. All the samples had one glass‐transition temperature and no crystalline regions. In addition, there were larger increases in glass‐transition temperature over the range of triol concentrations studied than over the range of NCO/OH ratios studied. For all samples, the Dibenedetto equation relating glass‐transition temperature to extent of crosslinking fit the data very well. Also, samples with higher crosslink densities had much larger elastic moduli for temperatures above the glass‐transition temperature. By assuming the system was a phantom network, approximate crosslink densities for stoichiometric samples were obtained from the dynamic mechanical data and these agreed fairly well with theoretical predictions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 212–223, 2002