Table 2.
Results of nanoindentation measurements performed on cured urea–formaldehyde-(UF) bond lines
| Adhesive | Number of indents [1] | Reduced modulus E r [GPa] | Hardness H [GPa] | Total indentation work W tot [pJ] | Ratio W e /W p [1] | Indentation creep C IT [1] |
|---|---|---|---|---|---|---|
| UF-1 | 36 | 10.24 ± 2.15 | 0.63 ± 0.11 | 44.95 ± 7.49 | 1.24 ± 0.32 | 0.14 ± 0.04 |
| UF-1 + 2% P1 | 37 | 9.52 ± 1.35 | 0.59 ± 0.11 | 45.39 ± 5.21 | 1.25 ± 0.24 | 0.14 ± 0.02 |
| UF-2 | 28 | 7.56 ± 1.42 | 0.40 ± 0.09 | 58.79 ± 8.42 | 0.77 ± 0.11 | 0.20 ± 0.02 |
| UF-2 + 2% P1 | 37 | 8.39 ± 1.45 | 0.42 ± 0.03 | 55.31 ± 2.66 | 0.79 ± 0.11 | 0.19 ± 0.01 |
W e /W p is the ratio of elastic to plastic deformation work, indentation creep (C IT) was defined as the relative change of the indentation depth while the applied load was kept constant. UF-1, UF-2 pure adhesives, UF-1 + 2% P1, UF-2 + 2% P1 adhesives filled with 2 wt% fibrillated beech pulp (P1)