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Author
Escobar Peral, Álvaro
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Abstract
Polyurethane reactive hot-melt adhesives are a type of adhesive whose demand in the market is in-creasing due to their good performance such as high green strength and high heat resistance. How-ever, these adhesives include large amount of unreacted monomeric diisocyanates, which can re-lease, when applied, toxic vapors for human health.
In the present work, polyurethane hot-melts based on prepolymerized isocyanates have been formu-lated, manufactured and analyzed to obtain adhesives with low free monomer content, having a final content lower than 0.1% by weight.
First of all, the prepolymerized isocyanates used in the present work have been analyzed in order to know their exact composition and free monomer content.
Then, some of the company's commercial products were reformulated with these isocyanates to an-alyze the variation in free monomer content and their final properties. A reduction of free monomer content was detected, however the decrease obtained was not sufficient.
Finally, with the aim of reducing even more the final free monomer content of the adhesive, the manufacture method has been further optimized with reformulations of the commercial products. On one hand, increasing their reaction time between polyols and isocyanates and, on the other, with the addition of catalyst to accelerate the reaction between polyols and isocyanates.
These last modifications in the manufacturing procedure gave promising results rendering a very low free monomer content. The decreased achieved is believed to give a major boost to the marketing of this type of adhesives based on polyurethane.
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