Characterization of polyisobutylene-based model urethane networks

✍ Scribed by Toshio Miyabayashi; J. P. Kennedy

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 541 KB
• Volume: 31
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1986.070310813

✦ Synopsis

Polyisobutylene-based model urethane networks have been prepared by crosslinking liquid a,odi(hydroxyl)polyi.vobutylenes, i.e., PIBdiols carrying exactly two =CH20H functions, F.

= 2.0 * 0.1, and rather narrow molecular weight distributions, MJM. = 12-1.6, with tritriphenylmethyl isocyanate HC&pCsH,-NCO),.

Networks prepared with M, = 1400 and 7500 PIBdiols, and with %/lo and 80/20 mixtures of these PIBdiols (bimodal networks), have been characterized by extraction, by the Flory-Rehner swelling method, and by the Mooney-Rivlinequilibrium modulus method, and tested by stress-strain measurements. M, values of the M, = 1400 PIBdiol network obtained by swelling (1550) and by equilibrium modulus studies (1500) were in excellent agreement with the M,, of the prepolymer. A h the C2 parameter was negligible in comparison to GI, suggesting the absence of intarchain entanglements. This is the first hydrocarbon-based polyurethane network that-exhibits a negligible Cz value by stress-strain measurements of unswollensamples. The M, values of the a, = 7500 PIBdiol were also in good agreement with the M. of the prepolymer; however, C2 was larger than C, , indicating interchain entanglements. Ecdence for strain-induced toughening was observed with both networks prepared with the M,, = 1400 and 7600 PIB-diols.

The ultimate properties of the two bimodal Eetworks did not show improvement over those of the individual constituents, however, the M,'s of the constituents were not very different.