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Nondestructive testing of defects in adhesive joints

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Table 4.6: DSC Results<br />

DSC thermo grams <strong>of</strong> edge sample, TETA cure, DDS cure, DDM cure.<br />

SL. NO. CURATIVE USED Tg(°C) ONSET OF<br />

TGDDM cured with DDM:<br />

EXOTHERMIC<br />

PEAK(°C)<br />

1 DDM 145.53 235.75<br />

2 DDS 113.71 240.49<br />

3 TETA(MIDDLE) 53.27 229.64<br />

4 TETA(edge) 85.97 227.04<br />

For TGDDM cured with DDM the Tg value was observed at 145.53°C. an exothermic<br />

peak starts at 235°C and reaches maximum exothermic heat flow at around 260°C. This <strong>in</strong>dicates<br />

that post cure at 210°C is not sufficient, still higher temperature is required for post cure. That<br />

may be around 250°C because exothermic peak reaches maximum at that temperature. Maximum<br />

exothermic temperature shown <strong>in</strong> DSC curves is the temperature at which the residual cure gets<br />

completed. At 280°C there is an endothermic peak. This may be due to some impurities gett<strong>in</strong>g<br />

evaporated at that temperature.

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