Bending properties of wood treated with a new organic wood preservative system
Introduction
Over the past 25 years, a plethora of new preservative systems have been introduced into the marketplace. In order for standards to be promulgated for these new systems, preservative treatments or treating regimens should not have a deleterious effect on wood properties. Many studies (Barnes and Winandy, 1986) have been conducted on the effect of various treatments on the mechanical properties of wood. For example, research by Winandy and others (Winandy et al., 1992, Winandy and Barnes, 1991, Barnes et al., 1990, Barnes and Winandy, 1989) recommended drying temperature limitations for CCA-treated wood, which were adopted by standards-setting organizations. Post-treatment conditioning cycles have varying effects on the resultant strength of wood depending on species, treatment, and type of conditioning. Losses in modulus of rupture from 8% to 33% have been reported depending on the steaming time, temperature, and preservative retention (Barnes, 1985). Other work has shown that ACQ and other treatments do not cause significant reductions in mechanical properties (Barnes et al., 1993, Barnes and Winandy, 1986). No practical deleterious effects of waterborne copper naphthenate treatment on the bending properties of southern pine have been observed (Barnes et al., 2005). Post-treatment steaming of copper naphthenate-treated pine had no practical negative effect on mechanical properties (Barnes and Linton, 2007). Other studies show no more than a treatment effect common with waterborne systems for other new copper-based systems like micronized copper azole and copper quat systems (MCA, MCQ) (Barnes et al., 2008c), copper xyligen (CX) (Barnes et al., submitted for publication), and copper betaine (Barnes et al., in press). This paper reports on the testing of southern pine treated with an all organic system, designated PTI, containing propiconazole (PPZ), tebuconazole (TEB), and imidachloprid (IMCP).
Section snippets
Materials
All sapwood, defect-free southern pine samples were cut from commercial kiln-dried dimension stock into samples measuring 38 mm × 38 mm × 610 mm (r t l). Samples were randomly assigned to three treatment groups such that each group would have a similar weight range, ring count, and earlywood/latewood ratio. The sample groups were shipped to Arch Wood Protection where they were treated and returned to the authors. A fourth group was retained as untreated control samples. Thirty-five samples were
Results and discussion
When unadjusted values were compared using the Student–Newman–Kuels’ test, no differences among any of the mean property values were shown. Consequently, the LS technique was used to separate means. Specific gravity was found to be a significant covariate in all analyses. Average treatment data are shown in Table 1. Summary data from the least squares analysis are shown in Table 2. In all cases these values have been adjusted for specific gravity.
The least squares comparison of modulus of
Summary
The data obtained in this study would indicate that no deleterious effect on bending properties was seen with PTI treatments used in this study, even for the highest retention. Additionally, the copper azole treatment (CA-B) used as a positive control show no negative effects when compared to control values. This result is similar to results obtained with other waterborne preservative systems except that no treatment effect was shown when comparing with untreated controls.
Acknowledgements
The authors gratefully acknowledge the sponsor of this research, Arch Wood Protection, Inc. This manuscript was accepted as Journal Article FP 421, Forest & Wildlife Research Center, Mississippi State University.
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