DELAYED CURING HIGH Tg CRASH DURABLE ADHESIVE
The invention relates to structural epoxy adhesives comprising an epoxy resin, a trifunctional epoxy resin; and a polyphenolic blocked polyurethane. The cured adhesives exhibit high Tg and good mechanical properties. The invention includes methods of making, and curing the adhesives, as well as the cured adhesive and article comprising the cured adhesive.
1 . An epoxy composition comprising:
a) a trifunctional epoxy resin;
b) a DGEBA epoxy resin;
c) a polyphenolic blocked polyurethane;
d) a filler;
e) a hardener; and
a curing accelerator.
2 . The epoxy composition of claim 1 , comprising 2 to 30 wt % of the trifunctional epoxy resin, based on weight of the epoxy composition.
3 . The epoxy composition of any claim 1 , wherein the trifunctional epoxy resin comprises an epoxy based on tris-(hydroxyl phenyl)-methane.
4 . The epoxy composition of any of claim 1 , wherein the trifunctional epoxy resin comprises a compound of formula:
5 . The epoxy composition of any of comprising 5 to 50 wt % liquid DGEBA epoxy resin, based on weight of the epoxy composition.
6 . The epoxy composition of any of claim 1 , comprising 0 to 20 wt % solid DGEBA epoxy resin, based on weight of the epoxy composition.
7 . The epoxy composition of any of claim 1 , comprising 10 to 30 wt % of the polyphenolic blocked polyurethane, base on weight of the epoxy composition.
8 . The epoxy composition of any of claim 1 , comprising 10 to 25 wt % of the filler, based on weight of the composition.
9 . The epoxy composition of any of claim 1 , comprising 3 to 7 wt % of the hardener, based on weight of the composition.
10 . The epoxy composition of claim 1 , wherein the hardener comprises dicyandiamide.
11 . The epoxy composition of any of claim 1 , comprising 0.2 to 1.5 wt % of the curing accelerator, based on weight of the composition.
12 . A cured adhesive composition obtained by curing the epoxy composition of claim 1 .
13 . The cured adhesive composition of claim 12 , wherein the curing comprises exposing the epoxy composition to a temperature in excess of 140° C.
14 . The cured adhesive composition of claim 12 , having a Tg at least 110° C.
15 . The cured adhesive composition of claim 14 , having a Tg at least 120° C.
16 . The cured adhesive composition of any of claims 12 , having an impact peel resistance of 8 to 25 N/mm.