Supplementary fibre supplies for the manufacture of MDF and particleboard. Part II. Feasibility study on manufacture of HDF using OSB fines as the raw material
An experimental work was carried out to evaluate the feasibility of using OSB fines as supplementary fibre resource to partially replace the commonly used wood fibre resource, such as SPF sawdust or shavings for the manufacture of high density fibreboards (HDF).
HDF was made with OSB fines with two different pre-treatments and five different mix ratios. Two pre-treatments of OSB fines were 24-hour water soak and steam preheating. The mix ratios of the OSB fines with SPF fibres included 0% as control, 25%, 50%, 75% and 100%. The panels were also made from green aspen sawdust or aspen chips. A total of 42 panels were made. The fibres were analysed for their fibre geometry, pH value and acid buffer capacity. The panels were evaluated with their internal bond strength (IB), modulus of elasticity (MOE) and modulus of rapture (MOR), thickness swell (TS), edge thickness swell (edge TS) and water absorption (WA) after 24-hour water soak, linear expansion (LE) and face screw holding.
The test results suggest that:
Stronger HDF panels could be made from OSB fines up to 75% in the mixture with SPF fibre as compared to those from SPF fibre, and were comparable to SPF panels when 100% OSB fines were used in terms of the mechanical and physical properties.
Comparing panels made from SPF, panels made from OSB fines had better properties in terms of panel dimensional stability. TS, edge TS, and WA reduced significantly with increasing OSB fines content.
Refining steam pressure significantly affected the panel properties. The lowest steam pressure used in the experiment resulted in the best panel properties.
The mechanical properties of the panels were improved with the pre-treatments of OSB fines. Comparing two different pre-treatments, pre-steaming was more effective than water soaking.
There was no significant impact on the panel properties, fibre quality and wood acidity due to the difference in raw material size and moisture content.
In general, under the similar refining process condition, no significant change in fibre length was observed when increasing mix ratio of OSB fines. However, the fines content in fibre was increased when increasing OSB fines content in the furnish. Comparing the fibre refined from 100% SPF to the fibre made with different contents of OSB fines, SPF fibre had the longest fibre length and the lowest fine content.
Fibre acidity was changed when using OSB fines. In general, the refined fibres become more alkaline with increasing OSB fines content.
The study shows that it is very important to identify suitable process conditions for using OSB fines since the optimal process condition for OSB fines would be significantly different from the one normally used for SPF wood.