Resorcinol formaldehyde latex (RFL) systems are among the most important finishes for high-strength yarns used in composites due to their very good adhesion properties. The most important industrial sector here is the rubber industry. However, due to the health hazards associated with the use of formaldehyde, there is an urgent need for more environmentally friendly and health-compatible processes for finishing with adhesion-promoting substances. In an AiF research project at the DITF, this task was taken up and the development and evaluation of formaldehyde-free adhesion promoter systems for industrial use was aimed at.
The sustainable, bio-based platform chemical HMF (5-hydroxymethyl-2-furfural) was selected as a promising alternative to formaldehyde and investigated with tests on a pilot plant dip system. HMF is toxicologically safe and very similar in reaction behavior to formaldehyde. In principle, HMF can therefore be used in applications comparable to those for formaldehyde. The evaluation of alternative, environmentally friendly fiber modifications on technically important cords compared to RFL adhesion promoters showed promising results in terms of adhesion strength (e.g. in the peel test) for fibers and rubber compounds that can be crosslinked by sulfur-based systems or by organic peroxides. Existing industrial standards could be met.