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Nondestructive testing of defects in adhesive joints

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content due to higher filler-polymer <strong>in</strong>teractions compared to untreated and silane-treated silica.<br />

PTh- and untreated-silica filled EPDM show similar levels <strong>of</strong> bound rubber content, lower than<br />

the silane-treated silica.<br />

PTh-silica filled EPDM (EPTh), SBR (SPTh), and NBR (NPTh) show self-cur<strong>in</strong>g<br />

behavior as shown <strong>in</strong> Fig. 2. This self-cur<strong>in</strong>g behaviour is due to the presence <strong>of</strong> sulphur moieties<br />

<strong>in</strong> the deposited PTh-film on the silica surface.<br />

Torque (dNm)<br />

16<br />

12<br />

8<br />

4<br />

SPTh (S: S-SBR; PTh: Plasma-thiophene coated silica)<br />

EPTh (E: EPDM; PTh: Plasma-thiophene coated silica)<br />

NPTh (S: NBR; PTh: Plasma-thiophene coated silica)<br />

0<br />

0 4 8 12 16 20 24 28 32<br />

Time (m<strong>in</strong>s.)<br />

Fig. 2: Self-cur<strong>in</strong>g behaviour <strong>of</strong> PTh-silica filled SBR, EPDM and NBR<br />

For all three polymers, tensile strength is <strong>in</strong>creased significantly due to the PTh-<br />

treatment. However, for SBR (SPTh) the addition <strong>of</strong> PTh-coated silica results <strong>in</strong> higher tensile<br />

strength as well as a higher modulus at 300% elongation and lower elongation at break values as<br />

shown <strong>in</strong> Fig. 3. This can be expla<strong>in</strong>ed by a better dispersion and filler-polymer <strong>in</strong>teraction as<br />

well as a higher crossl<strong>in</strong>k density.<br />

4

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