Researchers at NCPTT are discovering new treatments for historic stone conservation with the help of Hybrid Plastics, the University of Southern Mississippi, and a grant from the National Science Foundation. The team is developing new stone strengtheners, also called consolidants, based on the latest advances in polymer science. The National Science Foundation is awarding the partnership a grant of $360,000 for the three-year project.
The National Science Foundation’s grant enables NCPTT to bridge the gap between academic and federal research labs and private industry with this partnership. This collaboration brings together a unique combination of expertise and resources to address fundamental challenges in stone conservation that may ultimately advance the field of conservation and heritage science.
Commercially- available consolidants are on the market, but ever increasing restrictions on environmental regulations make it harder to use these products in an outdoor environment. Additionally, some of the products work better on materials like sandstone than on limestone or marble.
A little more than a year ago, NCPTT was facing the dilemma of cleaning and treating porous sugaring monuments in cemeteries. That’s when Joe Lichtenhan and Carl Hagstrom of Hybrid plastics paid the Center a visit. Hybrid Plastics is a young company pioneering the use of a new group of polymers based on modifying POSS (Polyhedral Oligomeric Silsesquioxane) molecules. Lichtenhan had the idea of using POSS polymers as treatments for deteriorating stone. Researchers at Hybrid plastics previously had successfully tested a POSS derivative as an adhesive on select grave markers in City Cemetery, Nashville, Tenn.
More recently, Derek Patton, an assistant professor at the University of Southern Mississippi, developed an interest in the project. Patton studies interactions of polymers and surfaces and has an interest in new ways to synthesize polymers. The University has one of the nation’s leading polymer science schools. Patton and his graduate students bring unique expertise to the team.
Proposed new stone consolidants are based on the POSS molecule’s ability to form a cage-like structure that provides strength and stability under a variety of environmental conditions. The polymers have properties that are similar to both ceramics and plastics. Depending on the modifications made to the molecules, the polymers can be used as adhesives, water repellents, or consolidants.
One important property of a consolidant is the “breathability” of the polymer. Water vapors must be able to move in and out of the stone easily. Water can cause stone to deteriorate between the polymer and the stone. NCPTT and its partners believe they have a way to create POSS polymers to treat stone without holding water. The new consolidants may be able to be cured using UV light, much like new dental adhesives. POSS polymers are unlikely to change the appearance of natural stone—a critical property for a stone consolidant.