The Influence Of Glass Transition Temperature On The Performance Of Acrylic Thermoplastic Adhesives

Acrylic thermoplastic resins are commonly used in conservation for consolidation and as adhesives. They are popular with conservators due to their reversibility and their considerable strength in moderately temperate environments; however, when used in an environment that exceeds their glass transition temperature (Tg), the adhesives will soften and flow, causing the adhered objects to slump or fall apart. The research presented here examines the performance of acrylic adhesives in environments with high heat exposure. Previous experiences of some conservators suggests that thermoplastic adhesives with a high Tg may not be appropriate for some substrates or fail after some years. It has been also suggested that the failure is due to their brittleness. Therefore, one of the aims of this research was to understand the relationship between glass transition temperatures and brittleness while continuing to provide reversibility and maintain strength. This paper presents results from experiments that tested the use of four acrylic thermoplastic adhesives and two mixtures of these adhesives to explore the effects of temperature on the performance and stability of these adhesives. Environmental simulations were performed using a temperature cycling chamber which was followed by four-point bending tests to assess strength and brittleness. The second part of the study tested the effect of temperature on the creep behavior of each adhesive. The results of this study will contribute to a better understanding of the long term behavior of adhesives in environments outside the climate controlled museum.