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A study of pre-treatments in the drying of regrowth Eucalyptus obliqua L'Herit

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Priadi, T (2002) A study of pre-treatments in the drying of regrowth Eucalyptus obliqua L'Herit. Research Master thesis, University of Tasmania.

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Abstract

This study investigated the potential of pre-treatment techniques to produce high
quality back-sawn boards from regrowth messmate stringybark (Eucalyptus obliqua
L'Herit), which is very prone to collapse and checking. Saturated urea solution,
one percent sodium hydroxide, four percent acetic acid, water, urea formaldehyde
resin (UF), and polyvinyl acetate glue (PVA) were used.
In Chapter 4, the experiment of chemical soaking pre-treatments showed that
soaking in sodium hydroxide solution for up to 15 days caused almost double
increase of boards' drying rate. However, this technique and soaking in acetic acid
solution caused more collapse and checks.
In Chapter 5 and 6, the surface coating experiment confirmed that coating with UF
resin did not significantly improve the drying properties of the boards. In contrast,
PVA coating prevented surface checking and considerably reduced edge checking
and collapse. The check value of these P boards was only a quarter the check value
of control boards.
In Chapter 6, the pre-treatments trial proved that significant reductions of
shrinkage and collapse were achieved mainly by urea soaking for eight weeks
(SSW boards). Both tangential and radial shrinkages of S8W boards were less than
half the shrinkages of control boards. The collapse free boards of S8W were
almost double amount of that in control boards. However, this pretreatment caused
more surface checks.
One-day urea soaking followed by eight weeks close stacking (C treatment)
reduced checking. The check free boards of C, W, and P were 38%, 25%, and
88%, while that of the control, S8W, and S2W boards were the same, 19%.
The average drying rates of W, S8W, and S2W boards were respectively 1.3 times,
0.4 times, and 0.6 times the drying rate of the control boards. The average drying
rates of P and C boards were almost the same as that of control boards (1.7 x 10-2
%/hour, in a four month drying trial).
This study indicates the prominent benefit of PV A surface coating in improving the
quality of dried back-sawn timber of regrowth messmate stringybark. Further
research, combining PV A coating and different drying process, such as high
temperature drying, is needed to produce high quality dried timber in a much
shorter time. This study also recommends water soaking when collapse and check
prone timbers cannot be kiln-dried immediately after sawing.

Item Type: Thesis (Research Master)
Keywords: Eucalyptus, Timber, Lumber
Copyright Holders: The Author
Copyright Information:

Copyright 2001 the author

Additional Information:

Thesis (MEngSc.)--University of Tasmania, 2002. Includes bibliographical references

Date Deposited: 03 Feb 2015 03:13
Last Modified: 06 Nov 2016 22:38
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