TWO-PART CURABLE COMPOSITION

1 - 20 . (canceled)

21 . A two-part curable composition comprising:

a) a first part (part A) comprising:

at least one cyanoacrylate monomer; and

b) a second part (part B) comprising:

a nucleophilic initiator, wherein said nucleophilic initiator is selected from the group consisting of organic bases, quaternary ammonium salts, metal salts of carboxylic acids, and mixtures thereof; and

a plasticizer;

said two-part curable composition further comprising a color changing indicator in part A and/or part B.

22 . The two-part curable composition according to claim 21 , wherein the at least one cyanoacrylate monomer is selected from mono-functional cyanoacrylate monomers, multi-functional cyanoacrylate monomers including bifunctional cyanoacrylate monomers, hybrid cyanoacrylate monomers, and mixtures thereof.

23 . The two-part curable composition according to claim 21 , wherein the at least one cyanoacrylate monomer is selected from the group consisting of methyl cyanoacrylate, ethyl cyanoacrylate, n-propyl cyanoacrylate, iso-propyl cyanoacrylate, n-butyl cyanoacrylate, sec-butyl cyanoacrylate, iso-butyl cyanoacrylate, tert-butyl cyanoacrylate, n-pentyl cyanoacrylate, 1-methylbutyl cyanoacrylate, 1-ethylpropyl cyanoacrylate, neopentyl cyanoacrylate, n-hexyl cyanoacrylate, 1-methylpentyl cyanoacrylate, n-heptyl cyanoacrylate, n-octyl cyanoacrylate, 2-octyl cyanoacrylate, 2-ethylhexyl cyanoacrylate, n-nonyl cyanoacrylate, n-decyl cyanoacrylate, n-undecyl cyanoacrylate, n-dodecyl cyanoacrylate, n-octadecyl cyanoacrylate, allyl cyanoacrylate, cyclohexyl cyanoacrylate, 2-methoxyethyl cyanoacrylate, 2-ethoxyethyl cyanoacrylate, phenoxyethyl cyanoacrylate, 2-(1-alkoxy) propyl cyanoacrylate, 2-(2′-alkoxy)-methoxyethyl-2″-cyanoacrylate, 2-(2′-alkoxy)-ethoxyethyl-2″-cyanoacrylate, 2-(2′-alkoxy)-propyloxypropyl-2″-cyanoacrylate, 2-(2′-alkoxy)-butyloxybutyl-2″-cyanoacrylate, 2-(3′-alkoxy)-propyloxyethyl-2″-cyanoacrylate, 2-(3′-alkoxy)-butyloxyethyl-2″-cyanoacrylate, 2-(3′-alkoxy)-propyloxypropyl-2″-cyanoacrylate, 2-(3′-alkoxy)-butyloxypropyl-2″-cyanoacrylate, 2-(2′-alkoxy)-ethoxybutyl-2″-cyanoacrylate, trimethylsilyethyl cyanoacrylate, trimethylsilypropyl cyanoacrylate, trimethylsilyloxyethyl cyanoacrylate triethylsilyloxyethyl cyanoacrylate, phenylethyl cyanoacrylate, and mixtures thereof.

24 . The two-part curable composition according to claim 21 , wherein part A of the two-part curable composition comprises from 50% to 99% by weight of cyanoacrylate monomer(s), based on the total weight of said part A.

25 . The two-part curable composition according to claim 21 , wherein part A further comprises at least one additive selected from the group consisting of an acidic inhibitor, a radical stabilizer, a thixotropic agent, a thickener, a toughener, an adhesion promoter, an accelerating agent, a filler, and mixtures thereof.

26 . The two-part curable composition according to claim 21 , characterized in that part A comprises:

from 85% to 95% by weight of cyanoacrylate monomer(s);

from 0.001% to 0.1% by weight of acidic inhibitor(s);

from 0.1% to 0.3% by weight of radical stabilizer(s);

from 2% to 10% by weight of thickener(s); and

from 2% to 10% by weight of thixotropic agent(s).

27 . The two-part curable composition according to claim 21 , wherein the nucleophilic initiator is selected from the group consisting of caffeine, calcium acrylate, barium acrylate, calcium stearate, 2-(morpholinothio) benzothiazole, and mixtures thereof.

28 . The two-part curable composition according to claim 21 , wherein part B comprises from 0.01% % to 1% by weight, of nucleophilic initiator(s) based on the total weight of said part B.

29 . The two-part curable composition according to claim 21 , wherein the plasticizer is selected from the group consisting of:

a) esters of C2-C4 carboxylic acids with C2-C5 alkyl alcohols having 2-4 hydroxyl groups optionally ethoxylated;

b) phthalates;

c) trimellitates;

d) adipates;

e) benzoates;

f) citrates;

g) sebacates;

h) (meth)acrylates monomers; and

i) mixtures thereof.

30 . The two-part curable composition according to claim 21 , wherein part B of the two-curable composition comprises from 50% to 99% by weight of plasticizer(s), by total weight of said part B.

31 . The two-part curable composition according to claim 21 , wherein the color changing indicator is in part B.

32 . The two-part curable composition according to claim 21 , wherein the color changing indicator is selected from the group consisting of:

Michler's hydrol;

pH indicator; and

mixtures thereof.

33 . The two-part curable composition according to claim 32 , wherein the pH indicator is selected from the group consisting of Bromocresol green, bromocresol purple, bromothymol blue, bromophenol red, m-cresol purple, o-cresol red, methyl yellow, methyl red, methyl orange, methyl violet, pentamethoxy red, pyrogallol red, thymol blue, Macrolex red, and mixtures thereof.

34 . The two-part curable composition according to claim 21 , wherein the color changing indicator is a pH indicator.

35 . The two-part curable composition according to claim 21 , wherein the pH of part B is higher than 6.

36 . The two-part curable composition according to claim 21 , characterized in that:

the two-part curable composition is colored after mixing of part A and part B, in the uncured state, and colorless or lightly-colored after curing; or

the two-part curable composition is colorless or lightly-colored after mixing of part A and part B, in the uncured state, and colored in the cured state; or

the two-part curable composition is colored with one color after mixing of part A and part B, in the uncured state, and colored with another color after curing.

37 . The two-part curable composition according to claim 21 , characterized in that the two-part curable composition is colored after mixing of part A and part B, in the uncured state, and colorless after curing.

38 . The two-part curable composition according to claim 21 , characterized in that the color changing indicator allows a loss of more than 70% of the color changing indicator's UV-absorption band at the wavelength where the absorption is maximum, between a colored uncured state after mixing part A and B after 60 seconds, and a cured state of the two-part curable composition.

39 . A method for bonding substrates using the two-part curable composition of claim 21 , the method comprising the steps of:

mixing together the two components of the two-part curable composition;

applying the mixing obtained above to at least one of the substrates, and

mating together the substrates for a time sufficient to permit an adhesive bond to form between the mated substrates.

40 . A method for determining cure of the two-part curable composition of claim 21 , comprising using a color changing indicator in the two-part curable composition.