As innovations in the rail sector emerge, adhesive bonding has become a key component in the manufacture of parts that offer superior performance and durability in rail vehicles and infrastructure applications.
For decades these objectives were achieved in part with adhesive solutions containing diisocyanates, a family of chemical building blocks mainly used to make polyurethane products.
Polyurethanes were preferred over other chemistries for their high initial tack, exceptional tensile strength, elongation (up to 600%), and high fatigue resistance. They also show effective resistance to rail cleaners, with no loss of mechanical properties, and do reasonably well in UV exposure for exterior applications.
But the use of these compounds will one day be restricted in Europe – and eventually elsewhere due to the Registration, Evaluation, Authorization and Restriction of Chemicals initiative, or REACH.
REACH calls for the progressive substitution of specific chemicals such as diisocyanates (referred to as "substances of very high concern" or SVHC) when suitable alternatives have been identified. Having entered into force in 2007, REACH provisions are being phased-in over 11 years.
To determine REACH compliance, companies must identify and manage the risks linked to the substances they manufacture or market to the European Union. They have to demonstrate to ECHA (European Chemicals Agency) how they’ve determined a substance can be safely used without harming the end customer.