Polyurethane adhesives are adhesives based on isocyanate chemistry. Polyurethane adhesives are also known as elastic adhesives, as they have extraordinary elasticity and elongation before fracture (up to 600%), but like epoxy adhesives, there are also rigid polyurethane adhesives, due to the high fracture toughness of these adhesives (up to 25 MPa). Elastic polyurethane adhesives cure by polyaddition reactions, acquiring a slightly cross-linked structure with the properties of an elastomeric material. Rigid polyurethane adhesives also cure by polyaddition but acquire a highly cross-linked structure with the properties of a thermosetting material.
One of the most important aspects of this industrial adhesive is its drying process.
It consists of two phases: a primary phase and a secondary phase in which it absorbs moisture from the environment or surrounding materials. For this reason, although it dries fairly quickly, the curing process of Pur Hot Melt can take between 24 and 72 hours.
Therefore, as it is a reactive adhesive, it needs moisture for this reaction to occur. This condition is usually present in both the air and the material to be bonded, so it is not usually a problem.
Pur hot melt adhesive differs from other adhesive products in that it can be used both indoors and outdoors thanks to its high resistance to moisture. In fact, it retains its cohesion from -40°C to 100°C.
Without a doubt, if you need an adhesive for difficult materials, Pur Hot Melt is the best choice. It is capable of providing good adhesion on non-porous materials and between different elements.