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Adya Singh, Tatjana Smolic, Elizabeth Dunningham

Adya Singh, Tatjana Smolic, Elizabeth Dunningham. Adding value to radiata pine wood: stiffness and dimensional stability enhancement by a novel process. Introduction. Pinus radiata , New Zealand’s important natural resource

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Adya Singh, Tatjana Smolic, Elizabeth Dunningham

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  1. Adya Singh, Tatjana Smolic, Elizabeth Dunningham Adding value to radiata pine wood: stiffness and dimensional stability enhancement by a novel process

  2. Introduction • Pinus radiata , New Zealand’s important natural resource • But it lacks stability and stiffness required in high value applications • High performance applications demand specific property improvements

  3. Objectives • To enhance dimensional stability and stiffness • To launch high value product in the market • Possible applications: furniture, joineries...

  4. Process development • A novel process developed to enhance stiffness through chemical treatment in combination with heat and compression

  5. Materials and Methods • Rotary peeled veneer • Dry sapwood • Veneer samples conditioned at 20C and 50% RH

  6. Zirconyl chloride treatment • 30 min soak in ZrOCl2x8H20 solution • Range of salt concentrations used (0.01-3.5%)

  7. 100mm 200mm • Veneers saturated and radially pressed to 40% compression • Pressing temperature 130°C • Pressing time 15 min

  8. Weverk press

  9. 3 point bend test (before and after compression) • Tensile test (compressed samples only)

  10. HT1 WS2 100 mm WS1 HT2 40mm TT 15mm Veneer sample cut up for testing

  11. HT1 WS2 100 mm WS1 HT2 40mm TT 15mm • Treated and compressed veneer was also tested • For dimensional stability (humidity cycling, and 24 hr water soak) • Surface hardness • Microscopically and • Chemically

  12. Scanning Electron Microscopy • Control uncompressed • Control compressed • Zr treated compressed

  13. Chemical testing • Zr content in treated veneer by ICP • carbohydrate content (CHO) analysis • NMR (not successful) • SEM-EDAX (not successful) • XPS (ESCA) (not successful)

  14. Compression and thickness reduction

  15. Changes in density

  16. Density before and after compression • Error bars represent one standard deviation

  17. Properties of unmodified radiata pine • Radiata pine is a medium density softwood • Dry timber (from 30 years old trees) has average density of 453kgm-3 , MOE=8.23GPa and MOR=85.8MPa

  18. Stiffness improvement • Overall improvement by bend test

  19. Specific stiffness of Zr treated compressed veneer • Modulus of Elasticity was normalised to specific value by dividing MOE with specific gravity • Stiffness improvement increased with increasing density • Salt concentrations did not increase stiffness • Error bars represent one standard deviation

  20. Stiffness and strength in tension Measured 12 months after initial MOE

  21. Humidity cycling conditions • 20°C& 65%RH • 25 °C & 90-96%RH • 25 °C & 30-40%RH • Thickness recovery (spring back) measured after humidity cycling

  22. Thickness recovery after humidity cycling

  23. Thickness recovery after 24 hours water soak

  24. SEM images • Uncompressed veneer showing normal appearance of axial tracheids and rays and radial files of axial tracheids

  25. Untreated compressed veneer showing considerable spring back of cells after water soak prior to block preparation (for microscopy)

  26. 3% ZrOCl2x8H2O treated and compressed veneer showing excellent compression retention after water soak prior to block preparation (for microscopy) • Note that compression extends throughout the entire thickness of veneer

  27. 3% ZrOCl2x8H2O treated and compressed veneer • The pattern of cell deformation is irregular, some cells are radially flattened but others deformed unevenly

  28. 3% ZrOCl2x8H2O treated and compressed veneer • Radial flattening of cells is evident in some parts • Cell walls are highly deformed but are largely intact with only minor cracks

  29. 3% ZrOCl2x8H2O treated and compressed veneer • Radial cell walls appear to be more deformed than tangential walls, with pit borders showing a range of deformities

  30. Chemical analysis • Concentration of Zr in 3% ZrOCl2x8H2O treated and compressed veneer was 0.278% on oven dried weight basis measured by ICP

  31. GC analysis of monosacharides • *could be compression wood

  32. Surface Hardness test • Error bars represent one standard deviation

  33. Conclusions • Compression fixation improved with an increase in the concentration of Zr (particularly at 3% and above) • Stiffness increased up to 150 % • Stiffness enhancement followed density increase • No loss in cell wall components • Mechanical damage to cell walls may have contributed to strength losses • Future developments to consider environmental issues and specific product applications • Potential for use of low grade radiata wood, e.g. juvenile wood

  34. Thank you!!!

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