Anaerobically curable compositions

An anaerobically curable composition comprises a hydroxy-functionalised mono(meth)acrylate, an aromatic mono(meth)acrylate that is not hydroxy-functionalised, a (meth)acrylate-functionalised polyurethane, and an anaerobic cure-inducing component. The composition may comprise 5-30 wt.% hydroxy-functionalised mono(meth)acrylate (e.g. hydroxyethyl methacrylate), 5-60 wt.% aromatic mono(meth)acrylate (e.g. benzyl methacrylate), 20-50 wt.% (meth)acrylate-functionalised polyurethane, and 5-15 wt.% polyethylene filler. The composition may be thixotropic with a viscosity of 500-3000 mPa.s and may comprise hydrophobic silica. Preferably, the molecular weights of the hydroxy-functionalised mono(meth)acrylate, the aromatic mono(meth)acrylate, and the polyurethane are 100-150 g/mol, 150-200 g/mol, and 5000-7000 g/mol, respectively. A method of sealing a joint between male and female mating parts comprises applying the composition to at least one mating part, joining the mating parts to form a joint, and curing the composition so as to seal the joint. Preferably, one of the mating parts is formed from a metal and the other from a plastics material.