Fibre-reinforced technical elastomer products are an integral part of everyday life and plant engineering. Applications range from tyres, conveyor belts and V-belts to bellows. They are made of high-strength fibre materials that are embedded in an elastic matrix. However, without the use of adhesion promoters to absorb the forces acting on them, the products will not perform adequately. These are applied to the yarns as a dip and fixed as a resin. Resorcinol/formaldehyde (RF) dips are frequently used. Due to the carcinogenic effect of formaldehyde and the unpleasant odour of resorcinol, the search is on for alternatives that come close to the price-performance ratio of RF systems. The same applies to predips, which are mainly used as an additional pre-treatment measure for non-polar PET or p-aramid fibres. In the state of the art, multifunctional isocyanates and epoxides play a key role here. Although these are highly reactive, they are also very toxic. The presentation will outline the work carried out at the DITF to successively replace the individual components with suitable compounds and process adaptations. In optimised dips, for example, formaldehyde can be replaced by 5-hydroxymethylfurfural and resorcinol by special active lignins or lignosulfonates. New predips based on crosslinkable anhydride-based reactive systems or innovative inline fibre activations using active oxygen species are interesting and sustainable approaches for producing composites with outstanding mechanical properties, especially for PET filament yarns.