Polyurethane adhesives are those glues that are made of urethane polymers with chemical based of isocyanate group also known as elastic adhesives, due they have an extraordinary elasticity and elongation before the fracture occurs (up to 600%), and also like epoxy adhesives exist rigid polyurethane adhesives, due to the high fracture resistance presented by these adhesives about 25 MPa.
The elastic polyurethane adhesives are cured by polyaddition reactions, taking on a slightly reticulated structure with properties of an elastomer material; rigid polyurethane adhesives are as well as cure by polyaddition but they also acquire a high crosslink structure of thermoset material.
There are 3 different types of polyurethane adhesives or glues:
2 component Polyurethane adhesives (Pur 2C)
1 component Polyurethane adhesives curing by heat (Pur 1C - heat) - Rigid polyurethane
1 component Polyurethane adhesives curing by moisture (Pur 1C - moisture) - Elastic polyurethane