Mechanical and thermal properties of UV-curable polyurethane and polyurea acrylates

✍ Scribed by Xuehai Yu; Brian P. Grady; Richard S. Reiner; S. L. Cooper

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 925 KB
• Volume: 49
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1993.070491110

✦ Synopsis

Soft-segment molecular weight, soft-segment crystallization, hard-segment-type, and reactive diluent level were examined in urea and urethane acrylates. Increasing soft-segment molecular weight led to a decreased tensile modulus, increased strength, and increased elongation at break. Soft-segment crystallization increased the modulus below the melting temperature, but decreased the modulus above the melting temperature because crystallization interfered with cross-linking. Materials with hard segments that allowed for greater phase separation showed a higher modulus, higher ultimate stress, and higher ultimate elongation. Materials with reactive diluents 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidinone ( NVP) showed qualitatively different behavior. HEMA caused the modulus and strength to increase with little effect on elongation up to concentrations of 50 wt %; at higher concentrations, the elongation decreased. NVP also increased the modulus and strength; however, at 40 wt % NVP, ultimate elongation increased in a well-phaseseparated system and decreased in a poorly phase-separated system. In tensile tests, samples with 40% NVP also showed substantial sample necking and drawing.