Enhancement of Physical and Mechanical Properties of Sugar Palm Fiber via Vacuum Resin Impregnation - Advanced Materials for Agriculture, Food and Environmental Safety - page 122

signii cant improvement (p ≤ 0.05) with the increase in pressure. h e tensile
strength increased from 243.77 MPa to between 251.39 and 297.67 MPa for PF
and between 287.84 and 344.71 MPa for UP. h e tensile modulus increased from
3.07 GPa to between 3.1 and 3.98 GPa for PF and between 3.15 and 3.98 GPa for
UP, while the elongation at break decreased from 25.16% to 17.66 and 6.26% for
PF and between 24.24 and 19.05% for UP. Low tensile strength and elongation at
break of PF-impregnated i bres showed that their i bers are inferior in toughness
(48.51 MJ/m 3 to between 33.08 and 12.29 MJ/m 3 ) compared to UP-impregnated
i bres (48.51 MJ/m 3 to between 57.56 and 45.21 MJ/m 3 ). h e outcome of this study
is a new technique for the enhancement of physical and mechanical properties of
natural i bers and their composites.
Keywords : Sugar palm i ber, Arenga pinnata, impregnation modii cation,
vacuum resin impregnation, impregnation pressure
5.1 Introduction
Natural i bers of er numerous advantages; they are abundantly available,
have high specii c mechanical properties, are low in cost, have low density,
are safe to handle, are not a threat to the environment, and are renew-
able and biodegradable [1-17]. Despite these advantages, they suf er from
some drawbacks due to the presence of hydroxyl groups (OH) in the i bre.
When natural i bres are exposed to high humidity, these hydroxyl groups
attract and hold water molecules through hydrogen bonding, which leads
to i ber swelling and causes the presence of voids at the composite inter-
face, resulting in deterioration in mechanical properties [18-20] and loss
in dimensional stability [21] of its i bers and composites. h is was proven
by the limited use of natural i ber composite products in indoor environ-
ments (where humidity is lower) compared to outdoor environments. In
composite processing, the addition of hydrophilic natural i bers to hydro-
phobic plastics results in a composite with poor mechanical properties
due to nonuniform i ber dispersion in the matrix and inferior i ber-matrix
interphase [22, 23]. h is is due to the fact that natural i bers are hydro-
philic in nature and generally contain large numbers of hydroxyl groups
which make them polar (A x OH: molecules with an -OH at one end), while
most hydrophobic polymer matrices are non-polar (C x A y : most carbon
compounds). Incorporation of these polar and non-polar characteristics
creates compounding dii culties that lead to nonuniform dispersion of
i bers within the matrix, which impairs the ei ciency of the composite
[20]. Besides contributing to the high moisture absorption of the i ber, the
polar nature also results in high moisture sorption in composites that leads