Lining and Consolidating Adhesives:Some New Developments and Areas ofFuture Research

This paper focuses on the light aging properties of heat-seal lining adhesives when used as solution-delivered consolidants, an investigation that is the first phase of a long-term research project. Because adhesives may yellow, discolouration related to aging is an important factor to consider when using adhesives as consolidants. The lining adhesive BEVA 371 is sometimes used for consolidation despite the fact that its photochemical stability does not appear to have been evaluated during its initial testing. In our work, BEVA 371 and 371b, along with alternative formulations with components that have been sourced or synthesized, are in the process of being evaluated qualitatively for their activation behaviour and analytically for their photochemical stability. The alternative tackifiers being considered are urea-aldehyde and hydrogenated hydrocarbon resins. These have low molecular weight and high glass transition temperatures (Tg), and offer improved photochemical resistance compared to the ketone resins found in the two BEVAs. Alternatives for other components, such as amorphous polyolefins and low Tg resins (which affect cohesion), are also being tested. Experimental formulations have been tested in accelerated light aging experiments and are being evaluated using Fourier transform infrared spectroscopy and solvent removability tests. Finally, synthesis of an ethylene vinyl acetate (EVAc) vinyl versatate (VVe) terpolymer is shown as a way to offer improved resistance to hydrolysis over EVAc copolymers used in conservation materials.