Environmental Engineering Reference
In-Depth Information
mechanical interlocking force between the i ber and the matrix is larger.
It encourages the uniformity of the polymeric structure, resulting in an
enhancement of the bonding strength between the polymer on the i ber
surface and the polymer matrix of the composite. In other words, the
impregnation modii cation improved the stress transfer between the i ber
and the matrix, which further improved bonding and mechanical proper-
ties of the composite. Enclosing the i ber surface has other benei ts such as
reducing defects and healing the surface l aws of the natural i ber, thereby
reducing the degree of anisotropy of the natural i ber and its composites.
Besides improvement in physical and mechanical properties, another
advantage of resin impregnation is that it increases i ber biological deg-
radation resistance. Without this resistance, prolonged water molecules
located in the cell wall can initiate degradation of the i ber cell wall. Low
MC is desirable to ensure natural i ber durability as opposed to a i ber
with higher MC, which promotes i ber decay. It is a well-known fact that
ambient MC, chemicals, and radiation ot en cause changes which result in
a slow drit in the physical and mechanical properties of i bers and their
composites [36-44].
Further evidence of improvement in physical properties via resin impreg-
nation was found when a signii cant reduction in water absorption (WA)
was seen at er the impregnated i bers were submerged into water for 24 h,
as shown in Figure 5.5. According to Chen et al . [19], at high humidity lev-
els, liquid water may be held by the forces of surface tension in capillary
spaces available in the material. With impregnation modii cation, the resin
ef ectively served as the i ber's barrier from dif usion of water molecules into
cell wall and capillary spaces (lumen), or at least it reduced the permeability
140
116.82 a
PF: y = -13.37x + 99.859
R 2 = 0.7222
UP: y = -13.554x + 101.9
R 2 = 0.7513
PF
UP
120
100
80
63.49 b
61.64 b
46.55 c
60
42.84 c
33.01 d
26.61 e
30.49 d
26.03 e
23.97 f
40
23.31 f
24.32 f
22.52 g
20
0
Control
1000
900
800
700
600
500
Impregnation pressure (mmHg)
Figure 5.5 WA of PF- and UP-impregnated sugar palm i bers at various impregnation
pressures.
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