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Nondestructive testing of defects in adhesive joints

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21. Bajsic G, Rek V. J Appl Polym Sci 2001; 79(5): 864-873.<br />

22. Gopakumar S, Nair MRG. Polymer 2005; 46(23): 10419-10430.<br />

23. Smith MJ, Peppas NA. Polymer 1985; 26(4): 569-574.<br />

Table I (NR/PEG) block copolymer sample specifications<br />

Block Copolymer<br />

NCO/OH ratio NR/PEG mole ratio<br />

NR/PEG (4000/4000) – 1 1.0 1<br />

NR/PEG (4000/4000) – 2 1.1 1<br />

NR/PEG (4000/4000) – 3 1.2 1<br />

NR/PEG (4000/4000) – 4 1.3 1<br />

NR/PEG (4000/4000) – 5 1.4 1<br />

Table II Equilibrium uptake values <strong>of</strong> the block copolymers <strong>in</strong> water<br />

Block Copolymer<br />

Equilibrium uptake<br />

(Q∞ mol%) values<br />

NR/PEG (4000/4000) – 1 9.45<br />

NR/PEG (4000/4000) – 2 10.47<br />

NR/PEG (4000/4000) – 3 7.78<br />

NR/PEG (4000/4000) – 4 8.61<br />

NR/PEG (4000/4000) – 5 4.72<br />

Table III Swell<strong>in</strong>g characteristics <strong>of</strong> NR/PEG block copolymers <strong>in</strong> water and at pH 4, pH 7<br />

and pH 9.<br />

Water pH 4 pH 7 pH 9<br />

Block Copolymer n k n k n k n k<br />

NR/PEG (4000/4000) – 1 0.47 2.43 1.09 0.42 0.97 0.36 1.03 0.35<br />

NR/PEG (4000/4000) – 2 0.42 6.63 0.74 2.78 0.74 2.43 0.60 4.79<br />

NR/PEG (4000/4000) – 3 0.60 6.58 1.22 0.76 0.92 1.86 0.92 2.15<br />

NR/PEG (4000/4000) – 4 0.59 4.38 0.88 1.90 0.73 3.01 0.70 3.28<br />

NR/PEG (4000/4000) – 5 0.61 16.99 1.14 3.55 0.90 6.25 0.67 53.76<br />

Unit: k x 10 2 gg -1 m<strong>in</strong> n .<br />

Table IV K<strong>in</strong>etic data on the solvent uptake by NR/PEG block copolymers <strong>in</strong> water.<br />

Block Copolymer k1 x 10 3 (m<strong>in</strong> -1 )<br />

NR/PEG (4000/4000) – 1 3.29<br />

NR/PEG (4000/4000) – 2 6.33<br />

NR/PEG (4000/4000) – 3 19.30<br />

NR/PEG (4000/4000) – 4 33.12<br />

NR/PEG (4000/4000) – 5 ⎯ a<br />

- a – negative value was obta<strong>in</strong>ed

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