4. Wood glue

Wood glue is an adhesive capable of tightly bonding pieces of wood together or with other materials [RE 11] . Many substances have been used historically as glues. They were all made from natural materials until the late 1940s, when synthetic glues were introduced, gradually surpassing natural glue. Wood adhesives can be classified into :

• natural glues: animal and vegetable glues (casein, soy, tannin and lignin) [RE 11] . They are known for their low water resistance;

• synthetic glues: derived from petroleum and other synthetic resins, these are artificial polymers that meet specific needs, such as superior resistance to humidity. Synthetic adhesives...