Analytical Observations Regarding Butvar B-98 and Paraloid B-72 Blends as a Suitable Adhesive in Hot Climates
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Analytical Observations Regarding Butvar B-98 and Paraloid B-72 Blends as a Suitable Adhesive in Hot Climates Paige L. Schmidt, Aaron Shugar, and Rebecca Ploeger Art Conservation Department SUNY Buffalo State College Rockwell Hall 230 1300 Elmwood Ave Buffalo, NY 14222 ABSTRACT An adhesive that can withstand elevated temperatures is necessary for the conservation of artifacts in hot climates. The use of Butvar B-98 as a modifier to raise the glass transition temperature of Paraloid B-72 was investigated. The characteristics of B-48N and B-72 blends, currently in use in the field of conservation, were used as a comparison for analysis of the B-98 and B-72 blends. Differential Scanning Calorimetry (DSC) was used to determine the glass transition temperatures (Tg) of the blends and shear testing was used to investigate the shear strength of the blends. While the B-98 and B-72 blends attained elevated glass transition temperatures and performed well during shear testing, issues regarding miscibility and phase separation of the blends were investigated using transmission FTIR, DSC, and optical microscopy. INTRODUCTION Multiple factors must be considered when selecting an adhesive to be used for the mending of artifacts in hot climates, especially without environmentally controlled storage spaces. Working properties such as tack, open time, and viscosity dictate the usability of an adhesive and its practicality for a conservator. Additionally, the long term stability of even the most easy to use adhesive must be examined before it can be recommended for use in conservation [4]. An important consideration for the long term stability of amorphous polymer adhesives in hot climates is glass transition temperature (Tg), which should exceed the highest temperature to which a mended artifact might be exposed. Several polymers, including cellulose nitrate, Paraloid B-72, Paraloid B-48N, and subsequent acrylic blends, have been used historically and in contemporary conservation as an attempt to fulfill the parameters required of archaeological adhesives in hot environments [6, 7, 16]. However, each of these adhesives has its own problematic characteristics. Finding an alternative adhesive or adhesive blend with more appropriate characteristics for use in hot climates would be beneficial to the field. One of the most ubiquitous adhesives historically used in archaeological ceramic conservation is cellulose nitrate, a semi-synthetic nitrated cellulose [16]. Dr. Charles Selwitz writes that “these relatively low molecular weight polymers [have] unique tackiness, thinness, and solvent release properties sought after in many conservation applications. Consequently, cellulose nitrate has found broad usage in art conservation” [16:2]. However, concerns regarding the life span of cellulose nitrate as a structurally sound adhesive for conservation have been
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