Two-part, cyanoacrylate/free radically curable adhesive systems

1. A two-part curable composition comprising:

(a) a first part comprising a cyanoacrylate component and an acidic component; and

(b) a second part comprising a free radical curable component and a peroxy acetal and/or ketal,

wherein the peroxy acetal and/or ketal is present in an amount from about 0.05 to about 5 percent by weight of the composition and is embraced by

wherein here R1, R2, R3 and R4 are each independently selected from hydrogen, C 1-6 alkyl, C 5-7 cycloalkyl, alkoxy, C 1-6 peroxy alkyl, C 5-7 aryl, and C 6-10 alkaryl, and R1 and R4 taken together form a cyclic ring with at least two peroxy linkages as part of the ring, wherein the peroxy acetal and/or ketal is one or more of:

A. wherein R1 and R4 are each tert-butyl and R2 and R3 are each hydrogen or cyclohexane;

B. wherein R1 is tert-butyl, R2 and R3 are each cyclohexane, and R4 is methoxy;

C. wherein R1 and R4 are each tert-butyl, R2 is ethyl, and R3 is methyl;

D. wherein R1 and R4 are each tert-butyl, R2 is phenyl, and R3 is ethyl;

E. wherein R1 and R4 are each tert-butyl, R2 is phenyl, and R3 is 1-phenyl methyl; and

F. wherein R1 and R4 are each tert-butyl, R2 is hydrogen, and R3 is 1-phenyl methyl.

2. The composition of claim 1 , wherein when Parts A and B are mixed together the acidic component liberates reactive species from the peroxy acetal and/or ketal thereby initiating cure of the free radical curable component.

3. The composition of claim 1 , wherein the cyanoacrylate component comprises H 2 C═C(CN)—COOR, wherein R is selected from alkyl, alkoxyalkyl, cycloalkyl, alkenyl, aralkyl, aryl, allyl and haloalkyl groups.

4. The composition of claim 1 , wherein the free radical curable component is selected from a (meth)acrylate component, maleimide-, itaconamide- or nadimide-containing compounds, or combinations thereof.

5. The composition of claim 1 , wherein the free radical curable component is a (meth)acrylate component selected from the group consisting of polyethylene glycol di(meth)acrylates, tetrahydrofuran (meth)acrylates and di(meth)acrylates, hydroxypropyl (meth)acrylate, hexanediol di(meth)acrylate, trimethylol propane tri(meth)acrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, benzylmethacrylate, tetraethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, di-(pentamethylene glycol) dimethacrylate, tetraethylene diglycol diacrylate, diglycerol tetramethacrylate, tetramethylene dimethacrylate, ethylene dimethacrylate, neopentyl glycol diacrylate, trimethylol propane triacrylate and bisphenol-A mono and di(meth)acrylates, and methacrylate-functional urethanes.

6. The composition of claim 1 , wherein the first part is housed in a first chamber of a dual chamber syringe and the second part is housed in a second chamber of the dual chamber syringe.

7. The composition of claim 1 , wherein at least one of the first part or the second part further comprises at least one of a plasticizer, a filler and a toughener.

8. The composition of claim 7 , wherein the toughener is a member selected from the group consisting of (a) reaction products of the combination of ethylene, methyl acrylate and monomers having carboxylic acid cure sites, (b) dipolymers of ethylene and methyl acrylate, (c) combinations of (a) and (b), (4) vinylidene chloride-acrylonitrile copolymers, (5) vinyl chloride/vinyl acetate copolymer, (6) copolymers of polyethylene and polyvinyl acetate, and combinations thereof.

9. The composition of claim 1 , wherein the first part and the second part are present in a ratio of about 1:1 by volume.