Polyurethane adhesive is a water-resistant glue used in bookbinding and woodworking. Different chemical combinations give rise to different properties, such as stiffness, density, and hardness. The adhesive was first developed in 1985 and has undergone several improvements, with the fourth generation having a low viscosity, high solidity, and curing time of a few seconds. It is sold under various brand names and is now available for general consumer use.
Polyurethane adhesive is a type of glue used in book binding and woodworking. Polyurethane is a class of polymers that are created from a chain of organic units, joined together with urethane links. A wide variety of polyurethane adhesive products are available. Different chemical combinations give rise to different properties. The chemical composition can be alerted to produce different levels of stiffness, density and hardness.
The main advantage of a polyurethane adhesive is that it is water resistant. This property makes it the glue of choice for bookbinders and book repair companies. The glue has a very low level of viscosity, cures within seconds and has a flexible state at room temperature. When used in terms of adhesives, cure time is the amount of time it takes before the adhesive has bonded the two.
As an adhesive, polyurethane was first developed in 1985. The first version had very specific properties. The adhesive was made available in 1988 and had a high viscosity, a low initial fastness level, but had a three day waiting period before it cured.
In 1996, the second generation of polyurethane adhesive was developed. Curing time has been reduced to less than three days while maintaining the low starting solidity levels and high viscosity. Further work was undertaken to reduce cure time while maintaining the characteristics that made the adhesive useful.
The next major improvement occurred in 2000. At this stage, the curing time was reduced to a maximum of 16 hours and a minimum of six hours. The solidity has been improved and the viscosity has been lowered to make it more commercial.
The fourth generation was made available in 2007. In this version the viscosity is much lower, the solidity remains the same as in the 2000, but the curing time is a few seconds. This change is crucial to both commercial success and long-term product utility.
In North America, polyurethane adhesive is sold under the brand names Gorilla Glue or Excel. Sales of polyurethane adhesives have expanded outside the specialty bookbinding industry. These products can now be found at any hardware store for general consumer use.
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