We use single component epoxy adhesive on our transformers to bond the ferrite cores together. This glue is applied as a dot of size of 3 to 4mm and a height of 0.5 to 1mm and cured at 160 degrees for 30 minutes.

We observe that after the glue has cured, it slowly starts developing a white patch (earlier it was transparent , clear) and after 24 to 48 hours the whole dot becomes white and the adhesion is totaaly lost and it peels of the surface. We have tried cleaning the surface the core, supplied dry air to dispensing equipments, changed the temperature and curing time but still the problem persists.

Could anyone let me know an answer and a solution for this problem.

V.B.Venkatesh
http://www.hical.com

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