Viscoelastic properties of Japanese lacquer film

Abstract

ABSTRACT: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.

Synthesis and Curing Behaviors of Cross-Linkable Polynaphthols from Renewable Resources: Preparation of Artificial Urushi

“…This transition might be caused by the main-chain motion of polynaphthol. The storage modulus was of 1 order of magnitude larger than that of natural urushi, indicating the formation of a tough cured film. A smooth trace of dissipation factor (tan δ) clearly suggests the homogeneous structure of the film.…”

A preliminary examination of urushi-based conservation options for the treatment of photodegraded Japanese lacquer using scanning electron microscopy and profilometry

“…As damage proceeds, microcracks propagate both vertically and horizontally leading to incremental loss of the surface and associated decoration such as makie particles and nashiji flakes (Yamashita & Rivers, 2011a). Progressive photodegradation is also associated with increasing sensitivity to solvents and fluctuations in RH (Ogawa et al, 1998;Obataya et al, 1999Obataya et al, , 2002McSharry et al, 2007McSharry et al, , 2011. Obataya et al (2002) inferred that raw urushi is more susceptible to photodegradation than processed urushi.…”

Curing behaviors of Korean Dendropanax lacquer determined by chemical and physical measures

“…In recent years, natural lacquers such as a cashew nut shell liquid (CNSL) lacquer and oriental ( Rhus vernicifera ) lacquer have attracted considerable interest because of the excellent protective and decorative properties. These have been used as surface coatings for wood, porcelain, metalware, and so forth 2–13. Over the past 45 years, synthetic lacquers have competed with natural lacquers.…”

“…Oriental lacquer is made from the sap of lacquer trees, Rhus vernicifera , primarily in Korea, Japan, and China. A number of studies have been made on the chemistry, curing behavior, film properties, and viscoelastic and surface morphological properties 7–13. More recently, many patents or studies related to the applications of CNSL and oriental lacquers have been published 2–13…”