Ensis Wood Processing THE JOINT FORCES OF CSIRO & SCION Adding value to radiata pine wood: stiffness and dimensional stability enhancement by a novel process Adya Singh, Tatjana Smolic, Elizabeth Dunningham

THE JOINT FORCES OF CSIRO & SCION

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

THE JOINT FORCES OF CSIRO & SCION Objectives  To enhance dimensional stability and stiffness  To launch high value product in the market  Possible applications: furniture, joineries...

THE JOINT FORCES OF CSIRO & SCION Process development  A novel process developed to enhance stiffness through chemical treatment in combination with heat and compression

THE JOINT FORCES OF CSIRO & SCION Materials and Methods  Rotary peeled veneer  Dry sapwood  Veneer samples conditioned at 20  C and 50% RH

THE JOINT FORCES OF CSIRO & SCION Zirconyl chloride treatment  30 min soak in ZrOCl 2 x8H 2 0 solution  Range of salt concentrations used ( %)

THE JOINT FORCES OF CSIRO & SCION  Veneers saturated and radially pressed to 40% compression  Pressing temperature 130°C  Pressing time 15 min 200mm 100mm

THE JOINT FORCES OF CSIRO & SCION Weverk press

THE JOINT FORCES OF CSIRO & SCION  3 point bend test (before and after compression)  Tensile test (compressed samples only)

THE JOINT FORCES OF CSIRO & SCION Veneer sample cut up for testing HT1 HT2 WS1 WS2 TT 15mm 40mm 100 mm

THE JOINT FORCES OF CSIRO & SCION  Treated and compressed veneer was also tested  For dimensional stability (humidity cycling, and 24 hr water soak)  Surface hardness  Microscopically and  Chemically HT1 HT2 WS1 WS2 TT 15mm 40mm 100 mm

THE JOINT FORCES OF CSIRO & SCION Scanning Electron Microscopy  Control uncompressed  Control compressed  Zr treated compressed

THE JOINT FORCES OF CSIRO & SCION Chemical testing  Zr content in treated veneer by ICP  carbohydrate content (CHO) analysis  NMR (not successful)  SEM-EDAX (not successful)  XPS (ESCA) (not successful)

THE JOINT FORCES OF CSIRO & SCION Compression and thickness reduction

THE JOINT FORCES OF CSIRO & SCION Changes in density

THE JOINT FORCES OF CSIRO & SCION Density before and after compression  Error bars represent one standard deviation

THE JOINT FORCES OF CSIRO & SCION 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

THE JOINT FORCES OF CSIRO & SCION Stiffness improvement  Overall improvement by bend test

THE JOINT FORCES OF CSIRO & SCION  Error bars represent one standard deviation 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

THE JOINT FORCES OF CSIRO & SCION Stiffness and strength in tension Measured 12 months after initial MOE

THE JOINT FORCES OF CSIRO & SCION 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

THE JOINT FORCES OF CSIRO & SCION Thickness recovery after humidity cycling

THE JOINT FORCES OF CSIRO & SCION Thickness recovery after 24 hours water soak

THE JOINT FORCES OF CSIRO & SCION SEM images  Uncompressed veneer showing normal appearance of axial tracheids and rays and radial files of axial tracheids

THE JOINT FORCES OF CSIRO & SCION  Untreated compressed veneer showing considerable spring back of cells after water soak prior to block preparation (for microscopy)

THE JOINT FORCES OF CSIRO & SCION  3% ZrOCl 2 x8H 2 O 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

THE JOINT FORCES OF CSIRO & SCION  3% ZrOCl 2 x8H 2 O treated and compressed veneer  The pattern of cell deformation is irregular, some cells are radially flattened but others deformed unevenly

THE JOINT FORCES OF CSIRO & SCION  3% ZrOCl 2 x8H 2 O 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

THE JOINT FORCES OF CSIRO & SCION  3% ZrOCl 2 x8H 2 O treated and compressed veneer  Radial cell walls appear to be more deformed than tangential walls, with pit borders showing a range of deformities

THE JOINT FORCES OF CSIRO & SCION Chemical analysis  Concentration of Zr in 3% ZrOCl 2 x8H 2 O treated and compressed veneer was 0.278% on oven dried weight basis measured by ICP

THE JOINT FORCES OF CSIRO & SCION GC analysis of monosacharides  *could be compression wood

THE JOINT FORCES OF CSIRO & SCION Surface Hardness test  Error bars represent one standard deviation

THE JOINT FORCES OF CSIRO & SCION 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

THE JOINT FORCES OF CSIRO & SCION