Enhancement of Physical and Mechanical Properties of Sugar Palm Fiber via Vacuum Resin Impregnation - Advanced Materials for Agriculture, Food and Environmental Safety - page 137

90

UP: y = -1.3385x + 54.336
R 2 = 0.4621

PF
UP

PF: y = -4.2373x + 39.787
R 2 = 0.9631

80

70

57.56 a

60 48.51 a 50.75 a

48.05 a

47.68 a 45.12 a 45.21 a

50

33.08 b

40

26.46 b

30

21.71 c

17.81 c

20

12.98 d

12.29 d

10

0

Control 1000 900 800 700 600 500

Impregnation pressure (mmHg)

Figure 5.13 Toughness of PF- and UP-impregnated sugar palm i bers at various
impregnation pressures

be strong and tough if it ruptures at high stress and exhibits high strain
values. In contrast, for a material low in toughness, it may be strong (has
high ultimate stress), but also has low strain values as found in brittle mate-
rials. High toughness translates to high stress and strain values and this
is a desirable property of i bers produced especially for composite rein-
forcement. Toughness is an important criterion for engineers to consider
when selecting, modifying, or designing new material that requires high
durability. It is also important during an impregnation process because
most impregnation modii cation, especially when using PF, results in an
increase in material brittleness. Although it is good to have materials with
high modulus that can resist deformation, most of the time it is a lot better
to have materials that bend instead of break, and if they bend, stretch, or
deform in some way, they do not break [62, 63]; therefore, it is important
to not focus solely on producing a i ber with a high modulus (as found
in PF-impregnated i bres) and high strength. It is also worth considering
producing a strong i ber that has high toughness.
In addition to toughness, it is also important to consider weight gain of
materials at er undergoing modii cation, as it can increase the i nal weight
of the end product (composite). h e PF-impregnated i bers show signii -
cant increases in SG (Fig. 5.2) as a result of a higher WPG (Fig. 5.1), while
no signii cant weight gain is shown in UP-impregnated i bers.
With regard to human safety and the environment, it is well known that
the formaldehyde emission of PF can have severe ef ects compared to UP. It
causes allergic reactions such as watery eyes, burning sensations in the eyes,
and many other side ef ects to human health, not to mention further prob-
lems for the disposal of formaldehyde waste. Although the lower molecular
weight of PF gives better penetration of resin molecules into the i ber cell