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    Fischer-Tropsch Wax

    Fischer-Tropsch wax, or FT wax, is a petroleum-derived hydrocarbon wax that is commonly used in EVA and metallocene based hot melt adhesive applications to adjust melting point, set time, and viscosity.  The problem with this wax is that the supply chain is very volatile because it is produced as a by-product of GTL processing of synthesis gas to synthetic liquid fuel.  There is a constant concern about a global shortage due to crude oil demand amongst manufacturers who use this hydrocarbon wax to produce adhesives.  Recently shortages have led adhesive manufacturers to search for an alternative wax in order to reduce the overall use of Fischer-Tropsch wax in their formulations.

Epolene® - An Alternative to FT Wax

Epolene® polymers are synthetic hydrocarbon waxes that are produced on purpose rather than as a by-product of GTL (gas-to-liquids) processing.  This makes Epolene® a much more reliably sourced wax than Fischer-Tropsch.  In response to requests from hot melt adhesive formulators, Westlake Chemical has evaluated hot melt adhesive formulations with Epolene® wax as a substitute for Fischer-Tropsch wax.  In these formulations the FT wax content has either been partially or completely substituted with the hydrocarbon wax Epolene® N-14 or Epolene® N-21.  The formulations with varying synthetic wax content that were tested are listed in the table below.
 
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Formulated Adhesive Comparison

The performance and properties of the adhesive formulations above were tested for the following properties:
  • Peel Adhesion Failure Temperature (PAFT)
  • Shear Adhesion Failure Temperature (SAFT)
  • Low temperature fiber tear
  • Open Time @ 177°C
  • Set Time @ 177°C
  • Melting Temperature (Tm)
  • Crystallization Temperature (Tc)
  • Brookfield Viscosity @ 149°C and 177°C

The properties of each hot melt adhesive formulation are compared in the graph below.
 
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Adhesion & Cohesion

All of the formulations resulted in hot melt adhesives with similar PAFT, SAFT, and low temperature fiber tear.  Full or partial substitution of Fischer-Tropsch wax with Epolene® wax is possible without any negative effects on the adhesive and cohesive performance of the formulation.

Open & Set Time

Substitution of FT wax with Epolene® resulted in hot melt adhesive formulations with a slightly longer open time.  Interestingly, complete substitution of FT wax with Epolene® N-14 resulted in the formulation with the most similar open time as the full FT wax formulation.  The set time of the adhesive formulations were relatively unchanged by substitution of FT wax with Epolene®.

Thermal Analysis

Partial and full substitution of FT wax with Epolene® N-14 resulted in a hot melt adhesive with a very similar thermal profile as the full FT wax formulation.  When FT wax was substituted for Epolene® N-21, however, the melting temperature of the resulting formulation was significantly higher than the full FT wax formulation.  The crystallization temperature of the formulations was unaffected by substitution of FT wax with Epolene®.

Viscosity

The viscosity of the hot melt adhesive formulation was slightly increased when FT wax was substituted with Epolene®.  The largest increase in viscosity was seen when FT wax was completely substituted with Epolene® N-14.

Summary & Conclusion

Finding a suitable replacement for Fischer-Tropsch wax in hot melt adhesive formulations has become more important as the supply for these hard synthetic waxes has become more and more unstable.  Epolene® polymers are polyethylene waxes that have shown to closely match the performance of FT wax without having a negative impact on hot melt adhesive properties.  Epolene® N-14 and Epolene® N-21 provide similar performance in hot melt adhesive formulations and are recommended as a substitute for Fischer-Tropsch wax.

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