Ensis Wood Processing THE JOINT FORCES OF CSIRO & SCION Adding value to radiata pine wood: stiffness and dimensional stability enhancement by a novel process.

Ensis Wood Processing

THE JOINT FORCES OF CSIRO & SCION

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

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 20C and

50% RH

THE JOINT FORCES OF CSIRO & SCION

Zirconyl chloride treatment

30 min soak in ZrOCl2x8H20 solution

Range of salt concentrations used (0.01-3.5%)

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

HT2WS1

WS2

TT15mm

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

HT2WS1

WS2

TT15mm

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

Target Solution Initial Compressed Compression Compress.

strength /%thickness/mmthickness/mm % %

control 2.63 1.58 40 400.01 2.64 1.71 35 400.1 2.68 1.61 40 401 2.64 1.51 43 40

2.5 2.68 1.52 43 402.7 2.64 1.59 40 403 2.59 1.38 47 40

3.4 2.69 1.56 42 403.5 2.51 1.51 40 40

THE JOINT FORCES OF CSIRO & SCION

Changes in density

Solution Initial Compressed Density strength density density increase

% g/cm3 g/cm3 %

control 0.401 0.621 550.01 0.390 0.594 520.1 0.371 0.600 621 0.389 0.622 60

2.5 0.441 0.712 612.7 0.395 0.631 603 0.371 0.601 62

3.4 0.416 0.659 583.5 0.437 0.656 50

THE JOINT FORCES OF CSIRO & SCION

Density before and after compression

Error bars represent one standard deviation

0

0.2

0.4

0.6

0.8

1

350.01

400.1

431

432.5

402.7

473

423.4

403.5

40control

Den

sity

(g

cm-3

)

not compressed compressed

Comp. Strain%Soln. Conc%

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

Solution initial MOE 3pt bendstrength MOE after compressonMOE increase

% Gpa Gpa %control 6.30 13.77 1190.01 5.37 13.55 1520.1 6.14 13.46 1191.0 6.08 14.72 1422.5 5.02 9.90 972.7 6.11 15.60 1553.0 7.70 17.77 1313.4 5.45 11.31 1083.5 7.15 11.28 58

THE JOINT FORCES OF CSIRO & SCION

Error bars represent one standard deviation

Specific stiffness of Zr treated compressed veneer

0

10

20

30

40

0.01 0.1 1 2.5 2.7 3 3.4 3.5

Soln conc.

MO

Es

(Gp

a)

Uncompressed Compressed

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

Solution bend tensile tensilestrength MOE MOE MOR

% Gpa Gpa Mpacontrol 12.5 13.24 53.55

0.1 11.09 12.66 50.261 15.25 17.52 47.02

2.5 10.15 13.09 19.762.7 13.56 12.60 25.283 19.24 14.24 33.24

3.5 14.88 13.56 24.71

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

21 2023

19

5

11

4 53

0

5

10

15

20

25

0 0.01 0.1 1 2.5 2.7 3 3.4 3.5

Soln conc.

Ave

rag

e th

ickn

ess

reco

very

%

THE JOINT FORCES OF CSIRO & SCION

Thickness recovery after 24 hours water soak

3128

3128

16 15 1411 12

0

5

10

15

20

25

30

35

0 0.01 0.1 1 2.5 2.7 3 3.4 3.5

Soln conc.

Ave

rag

e th

ickn

ess

reco

very

%

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% 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

THE JOINT FORCES OF CSIRO & SCION

3% ZrOCl2x8H2O 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% 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

THE JOINT FORCES OF CSIRO & SCION

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

THE JOINT FORCES OF CSIRO & SCION

Chemical analysis

Concentration of Zr in 3% ZrOCl2x8H2O 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

Sample Control Control Zr-chloride Zr-chloride SolidAverage % compressed replicate wood content (w/w) 3% 3%

Arabinose 1.44 1.53 1.27 1.01 1.44Xylose 6.3 6.1 5.9 5.7 4.8Mannose 12.2 13.3 11.8 9.2 12.1Galactose 1.7 1.6 1.6 5.3* 1.6Glucose 48.4 47.5 44 45.5 44.9Total 69.9 70 64.6 66.7 64.9

*could be compression wood

THE JOINT FORCES OF CSIRO & SCION

Surface Hardness test

1.351.12

1.04

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

ControlCompressed

Zr compressed Control

Dep

th o

f p

enet

rati

on

/ m

m

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