This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation, storage, etc. of polyurethane chain extender ML-400. This standard applies to ML-400 products produced by the reaction of formaldehyde with 2-chloroaniline and aniline through condensation, dehydration, distillation, filtration and other processes. The product is mainly used as chain extender and curing agent for polyurethane and polyurea elastomer (especially cast elastomer) products, and can also be used to cure epoxy resin.