what is glue made of

Glue can be made from various components, both natural and synthetic. Historically, glue was made from collagen obtained from animal parts, particularly horse hooves and bones. However, modern glues predominantly consist of synthetic materials such as polymers and resins, which provide strong adhesive properties and are more sustainable. In principle, glues are composed of an adhesive agent, additives (e.g., filling agent, resins, preservatives, moisturizers), and solvents. Natural adhesive agents like natural rubbers, starch, and casein are used, but synthetic adhesive agents are more commonly used. Additives are used to improve adhesive strength and the duration of storage life, and solvents are used to dissolve binding agents and additives to make the glue manageable. The constituents of glues differ per type and purpose of the glue. Additionally, there are glues that are solvent-free, where water is used to dissolve the binding agent and additives. The hardening processes of glues and the presence of additives to make the glue water-resistant depend on the type and purpose of the glue. Furthermore, there are two kinds of two-component glues available: glue based on polyurethane (PU) and the other based on epoxy resins, each suitable for different materials. Overall, while historically glue was made from animal-based collagen, modern glues are predominantly made from synthetic materials, providing reliable adhesive properties and being more sustainable.