Polymerisation initiators, polymerisable compositions, and uses thereof for bonding low surface energy substrates

Quaternary boron salts are used as initiators of polymerisation in adhesive compositions for bonding low surface energy substrates such as polyolefins. The quaternary boron salts are of the formula I wherein R1 is C1-C10 alkyl, R2, R3 and R4, which may be the same or different, are, C1-C10 alkyl or C3-C10 cycloalkyl, phenyl, or phenyl-substituted C1-C10 alkyl or C3-C10 cycloalkyl, provided that any two of R1-R4 may optionally be part of a carbocyclic ring, and M+ is a metal ion or a quaternary ammonium ion. Particular examples of initiator compounds include sodium tetraethyl borate and lithium tetraethyl borate, lithium phenyl triethyl borate and tetramethylammonium phenyl triethyl borate.