Biomedical Engineering Reference
In-Depth Information
h
f
(nm)
10
Ubl TMP
high I
8
Xylan
low I
6
4
Bl TMP
low I
2
0
50
100
150
200
250
Time (min)
Figure6.6
Thehydrodynamicthicknessof theformedhemicellulosefilmsoncelluloseasa
functionof time.
1.0
ref
xyl 100 mgl
−
1
ref
xyl 100 mgl
−
1
0.8
1
0.6
0.4
0.1
0.2
0.0
0.01
−
0.2
−
0.4
0
10
20
30
40
50
60
70
80
0
10
20
30 40
Distance (nm)
50
60
70
80
Distance (nm)
(a)
(b)
Figure6.7
The forcesmeasuredonapproach (a) andseparation (b) between twocellulose
beads across a reference solution (1mMNaCl, pH10) and a xylan solution (100mgml
−1
xylanin1mMNaCl,pH10). (ModifiedfromPaananenetal.2003.)
6.5.3
Effect of Xylan Adsorption on the Interaction between Cellulose Beads
Xylan adsorbs on cellulose in weakly alkaline solutions at low ionic strength and the
adhesion between cellulose surfaces decreases. The adsorption is observed in the force
curves as a stronger and longer-ranged repulsion on approach (Figure 6.7a), the range of
repulsion changing from less than 10 nm to approximately 60 nm. Adsorption of xylan
onto cellulose was supported by the QCM-D experiments (Figure 6.1). The slight pull-off
force around 0.1-0.4 mN m
−
1
observed between pure cellulose spheres is replaced by
a weak repulsion upon adsorption of xylan (Figure 6.7b). Both the force measure-
ment and the corresponding QCM-D results are described in greater detail in Paananen
et al
., 2003.
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