Use of an initiator
system comprising:a combination of an organoborane and a
polyaziridine, in a ratio ofaziridine groups to
boron atoms of greater than 1.3:1,as an initiator of polymerisation in an
adhesive composition for bonding a low
surface energy substrate;provided that the initiator
system does not contain more than a trace amount of a complex of organoborane with a complexing agent selected from:an amine other than a
polyaziridine;a complexing agent comprising at least one
hydroxide;a complexing agent comprising at least one
alkoxide; oramidine complexing agent.An initiator
system as described is of the formula VI: wherein R1 is C1-C10
alkyl,R2 and R3, 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-R3 may optionally be part of a carbocyclic ring;R5 is a polyvalent radical,R6 and R7 which may be the same or different are H or C1-C10 alkyl, particularly C1-4 alkyl, especially methyl, andy is a number of at least 2, particularly 2-4, especially 3, and the value of x multiplied by y is greater than 1.3.Particular examples of initiator compounds include, trimethylol
propane tris(3-(2-methyl aziridino))
propionate and trimethylol
propane tris-3-N-aziridinyl
propionate.