Enhancement of Physical and Mechanical Properties of Sugar Palm Fiber via Vacuum Resin Impregnation - Advanced Materials for Agriculture, Food and Environmental Safety - page 133

500

PF: y = 9.0093x + 234.81
R 2 = 0.9978

UP: y = 15.422x + 247.11
R 2 = 0.904

450

PF
UP

400

344.71 f

341.6 f

326.07 e

297.67 g

288.41 f

312.99 d

350

279.88 e

304.59 c

287.84 b

271.44 d

263.36 c

251.39 b

300

243.77 a

250

200

150

100

50

0

Control 1000 900 800 700 600 500

Impregnation pressure (mmHg)

Figure 5.8 Tensile strength of PF- and UP-impregnated sugar palm i ber at various
impregnation pressures.

It is shown in Figure 5.8 that the tensile strength of PF- and
UP-impregnated i bers signii cantly increased as the impregnation pres-
sure increased. It is more pronounced in the UP-impregnated i bers, as seen
in the regression trends. h e highest tensile strength of PF-impregnated
i bers was found at an impregnation pressure of 500 mmHg (297.67 MPa),
while for the UP-impregnated i bers it was at 600 mmHg (341.6 MPa) at er
no signii cant increase at 500 mmHg (344.71 MPa). It shows that the resin
that was enclosed and impregnated into the i ber cell wall not only acted
to improve physical properties, but at the same time it also increased the
strength of the i ber. h is is due to the fact that resin absorbed into the
i ber gave a reliable measure of the amount of substance in the i ber, which
reacted to stress. Since more added substances (such as PF and UP resins)
in the i ber provide more area to resist stress, a greater amount of added
substances resulted in a stronger impregnated i ber compared to the con-
trol sample; therefore, an increase in tensile strength is another important
advantage of i bers impregnated with PF and UP resins. Similar i ndings
were reported by many researchers [45-47] that show that resin impregna-
tion improved the strength of several lignocellulosic materials.
h e increase in tensile strength in i bers can also be explained by the
reduction of moisture content. When the i ber absorbed moisture and
dif used it into the cell wall, the water molecules started to form hydro-
gen bonds with the hydroxyl groups of the i ber, and the cellulose chains
moved apart, which resulted in an increase in microi bril size. h is caused
the change in the size of the cell, which in turn caused the i ber to swell.
As the celluloses inside the i ber moved away from each other due to i ber
swelling, large gaps between the cellulose chains resulted and weakened