Anatomy of a Copper Clad Laminate. Part III: Epoxy Resins

“The function of the resin is to act as a ‘glue’ to hold the laminate together. Epoxy resins can be purchased from various vendors at various steps of manufacture. Epoxy resin can be had in a liquid form so that it can be concocted to upstaged resin using proprietary recipes and processes.  It can also be purchased in the advanced or upstaged state, wherein the solid resin, complete with hardness and catalysts, is ready for use in treating.”

According to a FBI document date 20 August 1990 (classified SECRET):

This glass cloth laminate is manufactured using a Bisphenol A epoxy resin cured with Dicyandiamide.

A Memo from Det. Insp. Williamson dated 3 september 1990 states that:

“The glass cloth laminate is manufactured using a Bisphenol A epoxy resin cured with Dicyandiamide.”

“A feature of any interest in the manufacture of epoxy resin would be chemical used in the curing process. the In the Case of Production PT35 the curing chemical is dicyandiamide. This is the most commonly used chemical for this purpose in the industry and does not assist in identification.”

Here is an infrared spectrum  of Bisphenol A diglycidyl ether (commonly abbreviated BADGE or DGEBA)

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Here is an IR spectrum of Bisphenol A.

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And here is an IR spectrum of dicyandiamide

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Obviously, a good place to look for evidence of the dicyandiamide is around 2200 cm-1 and indeed the peak shows up on the spectrum of DP/347(a) taken at CIBA in early 1992.

Infrared Spectrum of DP/347(a) taken at CIBA in early 1992

 

The absorbance at 2210 cm−1 due to the C[TRIPLE BOND]N of the dicyandiamide is used for quantitative analysis of this material. (SEE Epoxy Resins: Chemistry and Technology, Second Edition, edited by Clayton May. P 1133). This absorption line has been shown to be very sensitive to curing conditions. To be continued…

REFERENCES

Application of FTIR on Epoxy Resins