Effective removal of aged protective coatings from natural heritage in yunyang using strong peelable hydrogels via enhanced interfacial interactions

Organic polymers such polyacrylates, silicones have been used to protect stone-based heritages. However, polymers degrade obviously with time which may lead to secondary damages to heritages. Removal of previously applied but now degraded polymers on stone surface becomes necessary for the long-term preservation of stone heritages. Current cleaning protocol is mainly based on dissolving or extraction of aged polymers by organic liquid, whose kinetics is dominated by the slow diffusion and dissolving processes at the interfaces. Such cleaning process is very time consuming and becomes almost not applicable in large area cleaning. In this work, peelable PVA-borate hydrogels are developed. Organic solvents are introduced to tune gel's mechanical strength and its interfacial adhesion strength. Aged polymer coating can be removed easily by mechanical peeling when appropriate adhesion forces between the gel and aged polymer coating are achieved. Such cleaning protocol has been successfully applied on a fossil wall around 1200 m². Details, precautions and limitations of this protocol is discussed in this work.