Random strandboards from mixed southern wood species were manufactured using calcium borate (CB) and zinc borate (ZB) as chemical additives and polymeric methylene diphenylmethane disocyanate (pMDI) as resin. There were four target levels of borate loading and two levels of resin content. Panel properties, including modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB) strength, linear expansion (LE), thickness swelling (TS), leachability, and swelling and strength retention properties under cyclic relative humidity, were measured. The influence of borate content, borate type, and resin content on various properties was analyzed.
It was found that the addition of borate negatively impacted the mechanical and physical properties of the boards. The influence of ZB and CB on both mechanical and physical properties was similar. The increase of resin content improved the properties significantly, especially TS. A certain portion of borate leached out from test samples under the water-soaking conditions. There was a higher initial leaching rate and the leaching rate decreased with the lapse of leaching time. Panels with higher initial borate loading level had higher leaching rate for all panel types. The leaching rates of ZB and CB treated samples were similar. The increase of resin content helped reduce TS and boron leaching. Compared with PF-bonded boards, leaching rate was significantly reduced for the pMDI-bonded panels. Under cyclic humidity exposure condition, the addition of borate negatively influenced the maximum TS, residual TS, and mechanical properties. The effects of ZB and CB on the maximum TS, residual TS, and mechanical properties were similar. The increase of resin content significantly reduced residual TS, but had no influence on maximum TS and mechanical properties. The addition of borate did not have significant influence on the strength retention of the boards under long term cyclic humidity exposure condition.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-06302004-134707 |
| Date | 01 July 2004 |
| Creators | Zhou, Yiqiang |
| Contributors | Cornelis de Hoop, Richard Vlosky, Qinglin Wu |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-06302004-134707/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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