Properties of pressure sensitive adhesives found in paper recycling operations

Hot-melt and water-based adhesives are very different materials with similar physical properties. Their ability to act as adhesives is due to physical bonds and mechanical interlocks which form as adhesive flows into topographical features on the substrate surface. Hot-melt adhesives are based on soft, rubbery polymers while water-based adhesives are usually acrylic latex emulsions. Both of these materials are soft and weak resulting in adhesive fragmentation during repulping. We have previously successfully modeled the behavior of hot-melts. The formulation and structure of water-based adhesives make them more susceptible to moisture when in storage, in use and in the recycling process, and thus, understanding their behavior is more difficult. Several experimental techniques have been developed to test how moisture is absorbed by adhesive and what effect water has on the performance of an adhesive material.