IntroductionPinus radiata , New Zealands important natural resourceBut it lacks stability and stiffness required in high value applicationsHigh performance applications demand specific property improvements

ObjectivesTo enhance dimensional stability and stiffness To launch high value product in the marketPossible applications: furniture, joineries...

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

Materials and MethodsRotary peeled veneerDry sapwoodVeneer samples conditioned at 20C and 50% RH

Zirconyl chloride treatment30 min soak in ZrOCl2x8H20 solution Range of salt concentrations used (0.01-3.5%)

Veneers saturated and radially pressed to 40% compressionPressing temperature 130CPressing time 15 min

Weverk press

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

Veneer sample cut up for testing

Treated and compressed veneer was also testedFor dimensional stability (humidity cycling, and 24 hr water soak)Surface hardnessMicroscopically and Chemically

Scanning Electron MicroscopyControl uncompressedControl compressed Zr treated compressed

Chemical testingZr content in treated veneer by ICPcarbohydrate content (CHO) analysisNMR (not successful)SEM-EDAX (not successful)XPS (ESCA) (not successful)

Compression and thickness reduction

Changes in density

Density before and after compressionError bars represent one standard deviation

Properties of unmodified radiata pineRadiata 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

Stiffness improvementOverall improvement by bend test

Specific stiffness of Zr treated compressed veneerModulus of Elasticity was normalised to specific value by dividing MOE with specific gravityStiffness improvement increased with increasing densitySalt concentrations did not increase stiffnessError bars represent one standard deviation

Stiffness and strength in tension Measured 12 months after initial MOE

Humidity cycling conditions20C& 65%RH25 C & 90-96%RH25 C & 30-40%RHThickness recovery (spring back) measured after humidity cycling

Thickness recovery after humidity cycling

Thickness recovery after 24 hours water soak

SEM imagesUncompressed veneer showing normal appearance of axial tracheids and rays and radial files of axial tracheids

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

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

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

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

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

Chemical analysisConcentration of Zr in 3% ZrOCl2x8H2O treated and compressed veneer was 0.278% on oven dried weight basis measured by ICP

GC analysis of monosacharides

*could be compression wood

Surface Hardness testError bars represent one standard deviation

ConclusionsCompression fixation improved with an increase in the concentration of Zr (particularly at 3% and above)Stiffness increased up to 150 %Stiffness enhancement followed density increaseNo loss in cell wall componentsMechanical damage to cell walls may have contributed to strength lossesFuture developments to consider environmental issues and specific product applicationsPotential for use of low grade radiata wood, e.g. juvenile wood