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Thin-strand composite panels and subsequent mass timber beams were produced using thermally modified wood strands in a pressurized system. The effects of thermal modification (TM) temperature and dwell time on the mechanical, moisture, and decay performance of panels were studied. TM reduced moisture sorption and increased decay resistance. The thin-strand composites were evaluated in flexure and benchmarked against commercially available structural products. Moreover, the mass timber beams’ out-of-plane bending was accurately predicted with traditionally used laminated beam theory. The study shows that TM, under controlled conditions, enables the production of high-performing wood-strand panels with improved dimensional stability and decay resistance.
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Feasibility of Manufacturing Strand-Based Wood Composite Treated with β-Cyclodextrin–Boric Acid for Fungal Decay Resistance
The feasibility of using β-cyclodextrin (βCD) as an eco-friendly carrier of boric acid for the protection of strand-based wood composites against decay fungi was evaluated. The formation of a βCD–boric acid (βCD–B) complex was confirmed by the appearance of the boron–oxygen bond by using attenuated total reflection–Fourier transform infrared spectroscopy. Chemical shifts of around 6.25 and 1.41 ppm were also observed in 1H Nuclear Magnetic Resonance (NMR) and 11B NMR spectra, respectively. The βCD–B preservatives at two levels (5 and 10 wt.%) were uniformly blended with southern pine strands that were subsequently sprayed with polymeric methylene diphenyl diisocyanate (pMDI) resin. The blended strands were formed into a loose mat by hand and consolidated into 25 × 254 × 12 mm oriented strand boards (OSB) using a hot-press. The OSB panels were cut to end-matched internal bonding (IB) strength and fungal decay resistance test specimens. The vertical density profiles (VDPs) of the IB specimens were measured using an X-ray based density profiler and the specimens with statistically similar VDPs were selected for the IB and decay tests. The IB strength of the treated specimens was lower than the control specimens but they were above the required IB strength of heavy-duty load-bearing boards for use in humid conditions, specified in the BS EN 300:2006 standard. The reduced IB of preservative-treated OSB boards could be explained by the destabilized resin upon the addition of the βCD–B complex, as indicated by the differential scanning calorimetry (DSC) results. The resistance of the OSB panels against two brown-rot fungi (i.e., G. trabeum or P. placenta) was evaluated before and after accelerated leaching cycles. The treated OSBs exposed to the fungi showed an average mass loss of lower than 3% before leaching, while the untreated OSBs had 49 and 35% mass losses due to decay by G. trabeum or P. placenta, respectively. However, upon the leaching, the treatment provided protection only against G. trabeum to a certain degree (average mass loss of 15%). The experimental results suggest that protection efficacy against decay fungi after leaching, as well as the adhesion of the OSB strands, can be improved by increasing the amount of pMDI resin.
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- Award ID(s):
- 1818090
- PAR ID:
- 10148769
- Date Published:
- Journal Name:
- Polymers
- Volume:
- 12
- Issue:
- 2
- ISSN:
- 2073-4360
- Page Range / eLocation ID:
- 274
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/polym12020274
