Effect of Extreme pH on Bond Durability of Selected Structural Wood Adhesives
Bibliographic record
Abstract
This is the second part of a two-part study aimed at examining the effect of extreme adhesive pH on bond durability. The first part dealt with short-term exposure and this second part dealt with long-term exposure. This part also included an examination of wood degradation by adhesive pH.Nine structural wood adhesives [four high pH phenol formaldehyde (PF), one intermediate pH phenol-resorcinol formaldehyde (PRF), two low pH melamine formaldehyde (MF), and two low pH melamine-urea formaldehyde (MUF)] were studied in terms of their pH effect on wood-adhesive bond durability using Douglas-fir wood substrate with specimens tested in block shear. The block shear specimens were initially subjected to vacuum-pressure treatment under water, followed by exposure, while wet, at 50°C for 0, 4, 8, 12, and 17 months. At each exposure period, the specimens were dried to their original moisture content prior to testing for shear strength and evaluation of wood failure.Indications of the extent of degradation of the wood layer adjacent to the bond line due to adhesive pH during the long-term exposure were also examined by the 1% sodium hydroxide solubility test. There were indications that the wood layer closest to the bond line, which contained included glue, had higher solubility compared to those farther from the bond line. This suggests that wood degradation and/or adhesive decomposition occurred and was considered to be induced by the adhesive alkalinity or acidity under the long-term exposure conditions.The PF showed the best durability performance followed, in decreasing order, by PRF and MF/MUF. The latter adhesives degraded completely after an exposure period of 8 to 17 months.The four PF adhesives passed the shear strength and wood failure requirements of the well-known North American structural wood adhesive standards indicating that their high pH had no significant detrimental effect on the wood-adhesive bond durability after the 17-month exposure period despite their being subjected to multiple cyclic tests. This observation was not apparent for the PRF, and the pH effect was considered inconclusive for the MF/MUF since they degraded during the exposure period.The results of this study provide support to wood adhesive standards that do not impose restriction on the upper spectrum of the pH range, and would be useful to adhesive standard developers. These results also serve as background information for adhesive companies in their formulation of wood adhesives as well as for bonded wood product manufacturers in their use of adhesives and for builders in their use of bonded wood products.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".