Waxes
The two main reasons to include waxes in hot melt adhesive formulations are to:
- Lower cost
- Reduce viscosity
Generally included at levels of 20-30% in hot melt adhesive formulations, properties
affected by the wax content are blocking characteristics, softening point, and open
time. The high melting microcrystalline waxes (m.p. 90°C) and synthetic waxes
(m.p. 100-120°C) are used because they contribute to high temperature properties
and greater cohesive strength. The high melting paraffin waxes (m.p. 65-70°C)
are used extensively in hot melt coatings for their barrier, anti-blocking and heat
seal properties, as well as their lower cost.
Figure 1 : Influence of wax preaging on EVA hot melt initial color
As with other organic materials, waxes are susceptible to autoxidation and will
lose their original properties if overlooked. Please reference the attached photo
illustrating, there is not only a significant improvement in the initial color of
the wax, but also in the overall color retention of the wax after aging. Other benefits
include enhanced viscosity stability and adhesive properties, all contributing to
the improved performance of the final hot melt adhesive.
