The Study of POSS/Polyurethane as a Consolidant for Fragile Cultural Objects

Xing Zhao,Meiman Peng,Lang Guo,Liping Zheng,Liqin Wang,Ziming Wang,Qing Niu

doi:10.3390/coatings12020153

Abstract

Moisture-curable polyurethane (MCPU) is a specifically designed material for the consolidation of fragile cultural objects in high-humidity environments. In order to solve the problem of its susceptibility to yellowing due to heat ageing, polyhedral oligomeric silsesquioxane (POSS) was added to the MCPU to prepare POSS/MCPU. The appearance, stability and mechanical properties of the POSS/MCPU films were characterized using a UV–Vis spectrophotometer, a gloss meter, a colorimeter, a thermal analyzer and a universal material testing machine. The results showed that the films are colorless and transparent and have a light transmission of over 80%. The addition of POSS has almost no effect on the chromaticity of the MCPU, while the thermal stability of the POSS/MCPU is improved compared to the pristine MCPU. The modified film is 2.50 times more resistant to yellowing by heat. The addition of POSS also simultaneously enhances the strength and toughness of the film. Using POSS/MCPU to reinforce the fragile object, the material was found to be significantly effective, indicating it has the potential to be used during the extraction of fragile cultural objects from archaeological sites.

Highlights

Cultural objects are physical carriers of human civilization and are a key to revealing the lost history of mankind
Menthol [12,13], cyclododecane and veratraldehyde [14,15,16] perform excellently when used for the extraction of fragile organic objects, but their use as temporary reinforcement materials generally requires secondary treatment, which can be damaging to fragile objects
Moisture-curable polyurethane (MCPU) was modified with polyhedral oligomeric silsesquioxane (POSS) as a stabilizer to produce POSS/MCPU, which exhibited excellent thermal stability and good reinforcement properties

Summary

Introduction

Cultural objects are physical carriers of human civilization and are a key to revealing the lost history of mankind. Epoxy resin has a high mechanical strength and is generally used for stone relics rather than fragile organic cultural objects. A novel moisture-curable polyurethane has been developed to address the challenges of extracting fragile organic cultural objects in high-humidity environments [17]. The material can be cured at 30–100% relative humidity to form a colorless, transparent film with a flat surface and excellent mechanical properties. It is effective for the reinforcement of fragile organic objects but is susceptible to yellowing under UV light and heat conditions. The effect of its application to delicate samples is investigated

Materials

2.10. Simulation Experiments

Treatment Results

Findings

Conclusions