Viscoelastic properties of Japanese lacquer film

✍ Scribed by Eiichi Obataya; Kenji Umemura; Misato Norimoto; Yoshitaka Ohno

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 190 KB
• Volume: 73
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19990829)73:9<1727::aid-app13>3.0.co;2-l

✦ Synopsis

The storage modulus (EЈ) and loss modulus (EЉ) of Japanese lacquer films were measured over a temperature range of Ϫ150 to 400°C. Three relaxation processes labeled ␣, ␤, and ␥ were detected at 80, Ϫ60, and Ϫ140°C, and their apparent activation energies (⌬E) were 63-91, 13, and 9 kcal/mol, respectively. These were attributed to the micro-Brownian motions of polymerized urushiol, the molecular motion related to the absorbed water, and the motions of methylene groups in the side chains, respectively. With aging at room temperature, the location of the ␣ peak shifted to higher temperature and its ⌬E value decreased. This result was ascribed to the autoxidative polymerization of urushiol. The EЈ of lacquer films increased with heat treatments at 100°C or above. When treated at temperatures below 200°C, the location of the ␣ peak shifted to higher temperature, with a reduction in the ⌬E value. Heat treatments at 200°C or above resulted in remarkable shrinkage and weight loss of films owing to the pyrolysis of lacquer constituents.