Hot-melt adhesive

Hot-melt adhesives can also be applied by dipping or spraying, and are popular with hobbyists and crafters both for affixing and as an inexpensive alternative to resin casting.

Amorphous adhesives deform easily, tending to dissipate most of mechanical strain within their structure, passing only small loads on the adhesive-substrate interface; even a relatively weak nonpolar-nonpolar surface interaction can form a fairly strong bond prone primarily to a cohesive failure.

The distribution of molecular weights and degree of crystallinity influences the width of melting temperature range.

Polymers with crystalline nature tend to be more rigid and have higher cohesive strength than the corresponding amorphous ones, but also transfer more strain to the adhesive-substrate interface.

Presence of unsaturated bonds makes the adhesive more susceptible to autoxidation and UV degradation and necessitates use of antioxidants and stabilizers.

[5] Materials containing polar groups, aromatic systems, and double and triple bonds tend to appear darker than non-polar fully saturated substances; when a water-clear appearance is desired, suitable polymers and additives, e.g. hydrogenated tackifying resins, have to be used.

[6] Increase of bond strength and service temperature can be achieved by formation of cross-links in the polymer after solidification.

This can be achieved by using polymers undergoing curing with residual moisture (e.g., reactive polyurethanes, silicones), exposure to ultraviolet radiation, electron irradiation, or by other methods.

[43] HMA are capable of bonding an array of different substrates including: rubbers, ceramics, metals, plastics, glass and wood.

[40] Today, HMA (hot-melt adhesives) are available in a variety of different types, allowing for use in a wide range of applications across several industries.

For use in industrial processes, adhesive is supplied in larger sticks and glue guns with higher melting rates.

[43] Examples of industries where HMA is used includes: Hot-melt adhesives are often sold in sticks or cartridges suited to the intended glue gun.