Method for bonding using one-component epoxy adhesive mixtures
Adhesive bonds are applied by mixing two adhesives with different properties and dispensing them to form bondlines between substrate pairs. The adhesives are then thermally cured and cooled. Varying the mix ratio permits one to vary the properties of the adhesive mixture so formed for use in bonding many different substrate pairs. The process allows potentially infinite variations of adhesive properties between those of the respective starting adhesives, simply by varying the mix ratio. The invention is especially adapted for use in manufacturing settings in which adhesives are to be applied in multiple places, but differing adhesive properties are needed among the various bonding areas.
1. A method of forming an adhesive bond
a) providing a first epoxy adhesive, wherein the first epoxy adhesive is a single component, thermally curable adhesive that when cured exhibits an elongation E 1 and an elastic modulus M 1 ,
b) providing a second epoxy adhesive, wherein the second epoxy adhesive is a single component, thermally curable adhesive that when cured exhibits an elongation E 2 and an elastic modulus M 2 such that E 2 >E 1 and M 2 <M 1 ;
c) combining the first and second epoxy adhesives at a volume ratio of 1:99 to 99:1 in a two-component dispensing apparatus, to form an adhesive mixture that when cured exhibits an elongation E 3 and an elastic modulus M 3 such that E 2 >E 3 >E 1 and M 2 <M 3 <M 1 ;
d) dispensing the adhesive mixture from the two-component dispensing apparatus and applying the dispensed adhesive mixture to form an adhesive bond at a bondline between at least one pair of substrates;
e) curing the adhesive mixture at an elevated temperature to form a cured adhesive layer at the bondline and
f) cooling the cured adhesive and at least one pair of substrates to below 40° C.
2. The method of claim 1 wherein in steps c)-e) are performed multiple times to apply the dispensed adhesive mixture to multiple pairs of substrates, and the volume ratio in step c) is changed at least once such that the adhesive mixture applied to at least one of the multiple pairs of substrates has a composition different than the adhesive mixture applied to at least one other of the multiple pairs of substrates.
3. The method of claim 2 wherein the adhesive mixture applied to at least one of the multiple pairs of substrates, when cured, exhibits an elongation E3a and an elastic modulus M3a which are different than the elongation E3b and elastic modulus M3b, respectively, of the adhesive mixture applied to at least one other of the multiple pairs of substrates.
4. The method of claim 2 wherein steps c), d) and e) are performed on a first substrate pair, and subsequently repeated on at least one subsequent substrate pair, wherein the mix ratio is changed when step c) is repeated on said at least one subsequent substrate pair.
5. The method of claim 4 wherein subsequent substrate pair exhibits more thermally-induced distortion than the first substrate pair, and the mix ratio is changed to include more of the second epoxy adhesive.
6. The method of claim 4 wherein the subsequent substrate pair exhibits less thermally-induced distortion than the first substrate pair and the mix ratio is changed to include less of the second epoxy adhesive.
7. The method of claim 1 wherein in steps c)-e) are performed multiple times to apply the dispensed adhesive mixture to multiple regions of a pair of substrates, and the volume ratio in step c) is changed at least once such that the adhesive mixture applied to at least one of the multiple regions has a composition different than the adhesive mixture applied to at least one other of the multiple regions.
8. The method of claim 7 wherein the adhesive mixture applied to at least one of the multiple regions, when cured, exhibits an elongation E3a and an elastic modulus M3a which are different than the elongation E3b and elastic modulus M3b, respectively, of the adhesive mixture applied to at least one other of the multiple regions.
9. The method of claim 7 wherein steps c) and d) are performed on a first region of a substrate pair, and subsequently repeated on at least one second region of the substrate pair, wherein the mix ratio is changed when step c) is repeated on said second region.
10. The method of claim 9 wherein second region exhibits more thermally-induced distortion than the first region, and the mix ratio is changed to include more of the second epoxy adhesive.
11. The method of claim 9 wherein the second region exhibits less thermally-induced distortion than the first region and the mix ratio is changed to include less of the second epoxy adhesive.