Enhancement of Physical and Mechanical Properties of Sugar Palm Fiber via Vacuum Resin Impregnation - Advanced Materials for Agriculture, Food and Environmental Safety - page 126

45

38.59 f

PF: y = 6.3609x + 0.7753
R 2 = 0.9872

UP: y = 3.1486x + 4.6967
R 2 = 0.9737

PF
UP

40

34.42 e

35

30

25.05 d

22.63 d

25

21.89 d

19.53 c

16.47 c

20

11.57 b

14.58 c

12.05 b

15

8.59 a

7.16 a

10

5

0

1000 900 800 700 600 500

Impregnation pressure (mmHg)

Figure 5.1 WPG of PF- and UP-impregnated sugar palm i bers at various impregnation
pressures.

to impregnation. h e WPG of the i ber signii cantly increased linearly as
impregnation pressure increased. h e highest WPG was found with the
i ber impregnated with pressure of 500 mmHg for PF and 600 mmHg for
UP. No signii cant increase was seen when the pressure increased to 500
mmHg. It was also observed that the increasing rate of WPG for i ber
impregnated with PF was higher than that of the i ber impregnated with
UP, as shown in the regression trend lines.
h e dif erent increasing rates can be explained by the dif erence in
molecular weights of the impregnation agents. Due to the low molecular
weight of the PF resin that was specially modii ed to be 500, it has shorter
branching in the polymer unit where it has smaller resin molecules that
allow the resin to penetrate into i ber cell wall. h is is in contrast with
UP, which has a higher molecular weight of 2000 [25, 26]. In order to have
better penetration of the resin, the molecule size of the resin must be suf-
i ciently small to penetrate deep into the cell wall, requiring the resin to be
unpolymerized or only slightly polymerized [27]. h e penetration of resin
into the i ber cell wall depends on several important factors such as the size
of the oligomer or polymer [28], sui cient time of immersion in resin, and
the impregnation pressure. It is also believed that higher molecular weight
resins might penetrate only into the cell lumen and not into the cell wall.
Bearing in mind that resin with a lower molecular weight has the tendency
to leach out from the cell wall, which can cause loss of cell wall bulking
ef ect [29], proper control should be taken on the impregnated i ber. Such
measures to prevent the resin from leaching out from the cell wall and cell
lumen of i ber include immediate polymerization of the resin at er impreg-
nation, or prepolymerization of the resin.