mapping adhesive infiltration in wood cell walls with ... wood adhesives... · mapping adhesive...

Mapping adhesive infiltration in

wood cell walls with synchrotron x-

ray fluorescence microscopy

Joseph E. Jakes, Chris G. Hunt, Dan Yelle, Warren

Grigsbya, Chuck Friharta Bioproduct Development, Scion, Rotorua, New Zealand

X-ray Fluorescence Microscopy

Sophie-Charlotte Gleberb, Stefan Vogtb

bX-ray Science Division, Argonne National Laboratory, Argonne, IL, USA

Wood Bonding and Moisture-

Induced Swelling

Stabilized

wood

surface

Adhesive

flexibility

Wood

Adhesive

High interfacial strain during moisture-induced

swelling can lead to bond failure

Wood

C.R. Frihart, Journal of Adhesion Science and

Technology, 2009, 23, pp 611–27.

Wood cells

Adhesive

Need methods for

cell walls

characterization

X-ray Fluorescence

Spectroscopy

Incident x-ray

L

M

K

Ejected electron

For medium- to

high-Z material,

the excess energy

is largely given off

as fluorescence

photons

Energy

dispersive

detector

system

Examples of XFM research:

B.S. Twining, S.B. Baines, N.S. Fisher, J. Maser, S. Vogt, et al.,

Analytical Chemistry, 2003, 75, pp 3806–16.

T. Paunesku, S. Vogt, J. Maser, B. Lai, and G. Woloschak , Journal of

cellular biochemistry, 2006, 99, pp 1489–502.

U.E.A. Fittschen and G. Falkenberg, Spectrochimica Acta Part B:

Atomic Spectroscopy, 2011, 66 pp 567–80


(XFM)Beamline 2-ID-E at the Advanced Photon Source at Argonne

National Laboratory


(XFM)Sample box at beamline 2-ID-E at the Advanced Photon Source at

Argonne National Laboratory

Wood cells

Adhesive

Tangential

Ra

dia

l

• Bromine-labeled phenol formaldehyde

(PF) adhesive

• 3-bromophenol instead of phenol

• Aliquots pulled at 5 times during

polymerization step

• Pristine tangential-longitudinal surfaces

bonded with Br-labeled PF

• Cured in 155°C for 45 min

• 2 µm-thick cross-sections cut with

diamond knife, floated in water, and

clamped inside foldable TEM grid

• XFM performed at 2-ID-E at the

Advanced Photon Source


(XFM)

15 keV x-ray

beam

Specimen

15°

Energy

dispersive

detector

Fluoresced

photons

Adhesive

Apx. 0.5 μm

spot size

Top View


(XFM)

15 keV x-ray

beam

Specimen

15°

Energy

dispersive

detector

Fluoresced

photons

Adhesive

Apx. 0.5 μm

spot size Primary

Br signal

(k-line)

Counts

Data analysis was carried out using the MAPS

software package. Briefly, full spectra were fit to

modified Gaussian, background was iteratively

determined and subtracted, and the results compared

to standard reference material (NBS 1832 and 1833,

NIST). S. Vogt, Journal de physique. IV, 2003, 104 pp 635–8.

0 2 4 6 8 10 12 14

Energy (keV)


(XFM)

15 keV x-ray

beam

Specimen

15°

Energy

dispersive

detector

Fluoresced

photons

Adhesive

Apx. 0.5 μm

spot size

Top View0.3 µm steps


(XFM)

10-1

101

102

104

106

50 µm 50 µm

Br signal Zn signal

Using TEM-EDXA Saka and Goring (1983) found 400

ppm Zn in CCML, but none in secondary cell walls

SEM EDXA results

50 µm 50 µm

Br EDXABackscattering

image

- XFM 2-3 orders of magnitude

more sensitive than SEM EDXA- No bremsstrahlung

background

- Although electrons are easier

to focus, x-rays have effectively

no side scattering

(log scale)

(µg/cm2)

XFM results

10-1

101

102

104

106

50 µm 50 µm

Br signal Zn signal

Using TEM-EDXA Saka and Goring (1983) found 400

ppm Zn in CCML, but none in secondary cell walls

(log scale)

(µg/cm2)

XFM results Potential artifacts

X-ray beam not perfectly focused

0.5 µm

Spatial distribution of x-rays

10-1

101

102

104

106

(log scale)

XFM results

50 µm

Br signal

(µg/cm2)

Potential artifacts

Br separates from Br-PF

Tested for free Br by: 1. Curing adhesive on filter paper

2. Soaking filter paper in water overnight

3. Tested water for Br ions using ion selective electrode and

total Br using ICP-MS

Up to 1% Br atoms fell off Br-PF and

became Br ions

50 µm

10-1

101

102

104

106

(log scale)

XFM resultsBr signal (µg/cm2)

50 µm50 µm50 µm50 µm

45 min 85 min 115 min 135 min 155 min

Decreasing amount of low MW PF

Tangential

Ra

dia

l

10-4

10-3

10-2

10-1

100

(log scale)

Br signal (normalized to Br phenol formaldehyde)

50 µm50 µm50 µm50 µm50 µm



Tangential

Ra

dia

l

10-4

10-3

10-2

10-1

100

(log scale)

Br signal (normalized to neat phenol formaldehyde)




-1 0 1 2 3 4 5

Distance (m)

10-3

10-2

10-1

100

101

Br

sig

na

ln

orm

aliz

ed

ton

ea

tP

F

10-4

10-3

10-2

10-1

100

(log scale)

Br signal (normalized to Br phenol formaldehyde)




Tangential

Ra

dia

l

10-4

10-3

10-2

10-1

100

(log scale)

Red lines indicate rows of cells

tested with nanoindentation




Nanoindentation Experiment

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

Depth

Lo

adInfinite half-space

Nanoindentation Experiment

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

0 50 100 150 200 250 300

Depth, h (nm)

0

200

400

600

800

1000

Lo

ad.

L(

N)

Depth

Lo

adInfinite half-space

Assess hardness and

elastic modulus0

0

A

PH

0A

SEeff

d

d

s

s

eff EEE

22 1111

S

1

P0

A0

Nanoindentation Procedure for

Wood• Nanoindentation surface prepared on

surface remaining after 2 µm-thick XFM

section removed

• Nanoindentation

• Hysitron TriboIndenter equipped with a

Berkovich tip

• Relative humidity (RH) controlled with RH

generator

• RH = 78% and dry air (<1%)

• Room Temperature

• 20-23°C

• Multiload indents

• Structural compliance method utilized• Jakes et al. (2008) J. Mater. Res. 23(4) pp. 1113.• Jakes et al. (2009) J. Mater. Res. 24(3) pp. 1016.

C

A

C

B

A

5 µm

A: S2 cell wall laminae

(S2CWL)

B: Compound corner middle

lamella (CCML)

C: Empty lumina

PF-filled lumen

Empty lumen

Empty lumenEmpty lumen

2 µm2 µm

Atomic force

microscopy (AFM)

images of residual

indents

PF-filled lumen

Empty lumen


2 µm2 µm

78%

RH

Structural compliance method used

to correct load-depth trace for edge

effects and specimen-scale flexing

Hardness (H) and elastic modulus

(Es) assessed from last seven

unloading slopes and averaged

PF-filled lumen

Empty lumen


2 µm2 µm

Dry air

78%

RH

Structural compliance method used

to correct load-depth trace for edge

effects and specimen-scale flexing

Hardness (H) and elastic modulus

(Es) assessed from last seven

unloading slopes and averaged

PF-filled lumen

Empty lumen

2 µm

Br XFM

image(log scale)

Zn XFM image

used as aid to

locate cell walls

10-4

10-3

10-2

10-1

100

PF-filled lumen

Empty lumen

2 µm

Br XFM

image(log scale)

10-4

10-3

10-2

10-1

100

Define ROI’s with

multiple indents

equidistant from

lumen edge

Zn XFM image

used as aid to

locate cell walls

0.00 0.05 0.10 0.15 0.20 0.25

Br signal normalized to neat PF

200

300

400

500

600

700

800

H(M

Pa

)

10

15

20

25

30

Es

(GP

a)

45 min85 min115 min135 min155 min

0.00 0.05 0.10 0.15 0.20 0.25


200

300

400

500

600

700

800

H(M

Pa

)

10

15

20

25

30

Es

(GP

a)


Dry air 78% RH

Each symbol type represents a different series

Each data point represents average properties within ROI

0.00 0.05 0.10 0.15 0.20 0.25


200

300

400

500

600

700

800

H(M

Pa

)

10

15

20

25

30

Es

(GP

a)


0.00 0.05 0.10 0.15 0.20 0.25


200

300

400

500

600

700

800

H(M

Pa

)

10

15

20

25

30

Es

(GP

a)


Dry air 78% RH

0.00 0.05 0.10 0.15 0.20 0.25


0.8

1.0

1.2

1.4

1.6

1.8

No

rma

lize

dH

0.6

0.8

1.0

1.2

1.4

1.6

No

rma

lize

dE

s


0.00 0.05 0.10 0.15 0.20 0.25


0.8

1.0

1.2

1.4

1.6

1.8

No

rma

lize

dH

0.6

0.8

1.0

1.2

1.4

1.6

No

rma

lize

dE

s


Summary

• Synchrotron-based XFM has sensitivity and spatial resolution to map out Br-labeled PF infiltrated into wood cell walls

• Higher MW PF (longer cook times) infiltrate less into cell walls near bondline

• Hardness and elastic modulus directly proportional to PF infiltration

• PF infiltration decreases moisture-induced softening of wood cell walls

Jakes, J.E., S.-C. Gleber, S. Vogt, C.G. Hunt, D. Yelle, W. Grigsby, C. Frihart. 2013. New

syncrotron-based technique to map adhesive infiltration in wood cell walls. In the Proceedings

of 36th Annual Meeting of the Adhesion Society held in Daytona Beach, FL, USA on March 3-6,

2013. Available online at http://adhesionsociety.org/program2013/


Induced Swelling

Stabilized

wood

surface

Adhesive

flexibility

Wood

Adhesive



Wood


Technology, 2009, 23, pp 611–27.

Wood cells

Adhesive

Need methods for

cell walls

characterization


Induced Swelling

Stabilized

wood

surface

Adhesive

flexibility

Wood

Adhesive



Wood


Technology, 2009, 23, pp 611–27.

We have methods

to map adhesives

and assess

hygromechanical

properties of cell

walls


Induced Swelling



We have methods

to map adhesives

and assess

hygromechanical

properties of cell

walls

Possible mechanisms to stabilize wood surface:

• Adhesive infiltration modifies water sorption

behavior of cell wall

• Chemical change (e.g. less –OH groups)

• Mechanical bulking

• Stronger cell walls swell less

• Increased strength from less water or

chemical modification?


Induced Swelling



We need methods

to quantify effect of

adhesive infiltration

on moisture-

induced swelling in

cell walls

Fundamental research questions:

• What is cell wall ultrastructure?

• How does cell wall swell with moisture?

• How does adhesive penetration modify

moisture-induced swelling at cell wall level?

• How are moisture-induced swelling forces

generated?

• What is the most efficient method to stabilize

wood surface?

• Increase or decrease mechanical

properties?

• Bulk cell walls? (whole cell different than

cut cell?)

• Chemically modify cell wall polymers?

• How deep into wood does stabilization need

to occur?

PF-filled lumen

Empty lumen

2 µm

10-4

10-3

10-2

10-1

100

Acknowledgements:•Tom Kuster (FPL) for SEM work

Questions?

mapping adhesive infiltration in wood cell walls with ... wood adhesives... · mapping adhesive...

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