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Nondestructive testing of defects in adhesive joints

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TGDDM/DDM SYSTEM:<br />

There are 2 transition temperatures observed <strong>in</strong> TGDDM/DDM system. This is due to the<br />

cyclization reactions occur dur<strong>in</strong>g cur<strong>in</strong>g 9 . Condensation <strong>of</strong> ma<strong>in</strong> cha<strong>in</strong> benzene r<strong>in</strong>g occurs to<br />

some extent, so the char yield is higher than the uncured res<strong>in</strong>, and from the high char yield value<br />

it is <strong>in</strong>ferred that this system will have good flame resistance<br />

TGDDM/DDS SYSTEM:<br />

There is only one transition temperature was observed <strong>in</strong> TGDDM/DDS system and<br />

residue obta<strong>in</strong>ed was 48%.this is attributed to the reason that complete condensation aromatic<br />

groups upon cur<strong>in</strong>g and this leads to very stiff and rigid network. From the highest value <strong>of</strong> char<br />

yield depicts that the material will have excellent flame retardancy.<br />

TGDDM/TETA SYSTEM:<br />

In TGDDM/TETA system also has only one transition temperature is observed and the<br />

residue was 14.33%. This char yield is less than the uncured res<strong>in</strong>. Onset <strong>of</strong> degradation and it<br />

loses the maximum weight <strong>in</strong> a little <strong>in</strong>terval <strong>of</strong> temperature. TETA cur<strong>in</strong>g system is meant for<br />

room temperature cur<strong>in</strong>g it is not suitable for the high temperature cur<strong>in</strong>g. TGDDM is a high<br />

temperature cur<strong>in</strong>g, so it does not yield good properties with TETA cur<strong>in</strong>g agent.<br />

Sl.no Cur<strong>in</strong>g<br />

system<br />

1. Uncured<br />

res<strong>in</strong><br />

Table 4.5: Comparison <strong>of</strong> cur<strong>in</strong>g systems<br />

Temp. at<br />

10%<br />

weight<br />

loss(°C)<br />

Char yield (%)<br />

200°C 400°C 600°C 800°C<br />

157.4 83.75 46.66 26.36 20.57<br />

2 DDM 251 98.125 62.1875 33.125 28.75<br />

3 DDS 305.89 98.398 71.63 51.06 46.91<br />

4 TETA 274.25 95.01 24.78 14.52 14.13

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