What is a Hot Melt Pressure Sensitive Adhesive

With a global market worth several billion dollars a year, pressure sensitive hot melt adhesives play a huge part in the modern lifestyle, used in everyday industries from automotive to bedding to labelling and so on. With the trend away from solvent borne adhesives, this growth seems likely to continue. Yet the complex behaviour behind this class of adhesives can make the formulation of them seem more of an art than a science.

This post is intended as a brief overview of their characteristics, constituents, advantages, pitfalls, and the myriad testing methods for this fascinating family. To receive the full, technical details, fill out the form at the bottom to have our whitepaper sent to you.

Definition of a pressure sensitive hot melt

Let’s start with defining our subject, not least because it is the title of this piece. Pressure sensitive adhesives are generally described as non-reactive adhesives which form a bond between two surfaces when pressure is applied. The hot melt part differentiates these from adhesives that use water or another solvent as a medium which evaporates after coating out onto a surface leaving a pressure sensitive coating. Hot melts achieve this by simply melting down until they are fluid enough to coat out or spray. Because of this, the whole of the adhesive is usable rather than say, 40% in a solvent-based product with 40% solids content.

 Pie chart of contents of a pressure sensitive hot melt

Comparison of pie charts of typical pressure sensitive hot melt (above) to EVA based hot melt (below). Apart from using rubber polymers instead of EVA, these grades often have oil as a diluent instead of wax to retain tack when at ambient temperatures. This particular PSA formulation also has a quantity of filler which is sometimes used to keep the price competitive.

To learn the main differences between pressure sensitive hot melt adhesives and conventional packaging hot melts, as well as all the other things that go into making pressure sensitive hot melts such a huge player in today's world, fill out the form below to have our full technical whitepaper emailed to you.