Sunday, June 15, 2008

Curing at Elevated Temperature

Although most of the bonding that is done with resorcinol adhesives is carried out at ambient air temperature, elevated temperatures naturally accelerate the rate of curing. It is often asserted that it is inadvisable to cure a resorcinol resin above a temperature of about 70o-80o C. There would appear to be no fundamental reasons for such a temperature limit except that at high temperatures, the depolymerization of the para formaldehyde hardener is rapid, and the evolution of gaseous formaldehyde may result in foaming taking place in the glued joint. It is therefore desirable to liberate the formaldehyde more slowly; this may be accomplished by using as a source of formaldehyde methylol compounds such as methylol melamine of urea, or low molecular weight condensates derived from these which are relatively unstable and at elevated temperature split off formaldehyde. And at a temperature of 130oC or even higher, a source of formaldehyde and afford satisfactory and excellent adhesive strength.

Curing temperature is the temperature when the adhesive or resins is changed to their stabile structure. After over this temperature, the resin or adhesive form their own stabile condition and can't change or reprocess again. If the resin then formed a plastic material, then this plastic will have irreversible properties, the plastic itself called thermoplastic.

Next to Filler Adhesive.

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