The susceptibility of non-veneered composite panel products to decay is greater than solid timber when exposed to high moisture contents and severe decay hazard conditions. Preservative chemicals incorporated into these products at various stages of manufacture generally improve the decay resistance of these materials but certain strength properties, especially internal bond, are adversely affected. It appears from the literature survey that treatment of the composite panel products with ACA type preservative system could provide adequate protection with acceptable loss in the strength properties of the panels.
This project is the conclusion of a study begun in 1982 to investigate some aspects of the development and collection of moisture in exterior walls. The purpose of this project is to monitor the behavior of the test walls through their dry-out of moisture collected during the winter of 1982-83. These walls had been installed in the exterior wall of the materials testing laboratory at Forintek's Eastern Laboratory. The test walls which have been included in this study consist of variations on conventional walls, some of which have had particular problems in electrically heated houses in Newfoundland and other areas. The main research goal in this study has been to demonstrate the effect of minimizing air exfiltration into walls. The indoor environmental conditions are reasonably severe while the exterior conditions have the advantage of being produced by natural conditions. The benefits of this study are that a better understanding of the causes and cures to the problems will be attained. It may be possible to subbest how the problems may be avoided in future construction, and how they may be corrected in already-built housing. It may also be possible to help some building products recover and maintain markets for their use. One such product is hardboard siding which has suffered much criticism and loss of acceptability for reasons that are probably not related to the product or to the way it was used.
The study tour to Norway and Sweden was planned and coordinated by Russell C. Moody and Anton TenWolde from the U.S. Forest Products Laboratory. Forintek Canada Corp. was invited to participate on the tour with them with a view to beginning cooperative planning and research in areas of environmental concern, specifically moisture management in wood framed structures. The tour took place from August 17 to September 1, 1983. The author also stopped off in England to visit the British Research Establishment Laboratory in Princes Risborough and the TRADA laboratory in the same vicinity. Special appreciation is accorded to Mr. Torbjorn Schmidt at the Swedish Forest Products Laboratory in Stockholm and Mr. Erik Aasheim at the Norwegian Institute of Wood Technology. Their recommendations and assistance in setting up visits and tours was of great help. Mr. Schmidt also accompanied us in some of our journeys in Sweden and joined us in Norway for some of our meetings there.
Scanning electron microscopic observations of treated and untreated wood residues of poplar and eucalyptus were carried out. We hoped to evaluate the different methods of treatment and study the effect that different conditions such as temperature, time, pressure and chemicals have on the physical modification of the wood residues. It was observed that wood samples which had been treated by continuous acid hydrolysis in a Cascade reactor at temperatures below 243C and discharge pressure below 4000 psi had little effect on the wood structure. At a moderate discharge pressure (2975 to 2500 psi), the degree of wood disruption increased with the increase in reactor temperature; thus more of the wood tissue was reduced to wood fibers and fiber bundles at 223C than at 208C. Although wood samples retained in the ractor for shorter times than 100 sec showed insignificant morphological changes, longer retention times may increase the outflow of lignin from the cell wall layers. Tetrahydrofluran was shown to remove the lignin deposits in the treated wood. Wood samples discharged from the reactor and subsequently washed with tetrahydrofluran showed clean fiber surfaces and separation of the fibers as fault lines developed among the fiber bundles. The wood samples of E. saliqua were more resistant to pretreament as compared to the samples from poplar wood. The process of liquefaction was shown to effectively alter the wood structure of poplar. The poplar wood chips which were treated at 320C for 5min followed by discharging at 520 psi contained shattered tissue fragments and associated spheres. Cellulose microfibrils however were not found in these treated wood samples.
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