Civil Engineering Reference
In-Depth Information
as high aspect ratio and their nanometer scale dispersability, contributes to good rein-
forcement and improves the mechanical properties of the biocomposites [8-10]. When
polymer is intercalated and exfoliated into layered nanoclay platelets, the mechanical,
heat resistance and high barrier properties and l ammability resistance are improved
compared to the conventional biocomposites [11, 12].
Natural i bers are biodegradable reinforcing materials which can be used as alter-
natives to synthetic i bers such as glass and carbon i bers. Natural i bers are environ-
mentally-friendly, low cost, easily and widely available, and have high specii c strength
and modulus, etc. [13, 14]. Kenaf i ber (KE) is a warm season annual i ber crop closely
related to cotton and jute. h e KE has a single, straight, branchless stalk, and is derived
from the outer i brous bark as bast i ber. Kenaf i ber is composed of approximately
45-57% cellulose, 21% hemicelluloses, 8-13% lignin and 4% pectin by weight. It is
being applied to commercial products in various i elds such as automotive materials,
mobile phone housing and electronic component materials, etc., due to its lightweight
and excellent mechanical properties compared with other natural i bers [2, 15, 16].
h e performances of biocomposites depend on several factors, including chemical
composition, cell dimensions, defects, structure, the physical and mechanical proper-
ties of the natural i ber, and also the adhesion between natural i bers and the polymer
matrix. Furthermore, the high aspect ratio of length/width is a very important factor
for mechanical properties because the load transfer is performed primarily through
the interface between natural i ber and polymer matrix. Liu
et al.
[17] reported on the
inl uence of injection or compression molding methods and i ber length on thermal
and mechanical properties of kenaf-reinforced soy-based biocomposites. It was found
that the modulus, impact strength and heat del ection temperature of kenaf-reinforced
soy-based biocomposites increased with longer i ber length, higher i ber content of
kenaf i ber and i ber orientation. Bledzki
et al.
[18] studied the ef ect of dif erent i ber
lengths (5, 25 and 40 mm) and compounding processes of abaca i ber-reinforced PP
composites. It was observed that, with an increase of i ber length, the tensile and l ex-
ural properties showed a tendency to increase, and the mixer-injection molding pro-
cess displayed a better mechanical performance than the other processes. Takagi and
Ichihara [19] examined the ef ects of i ber content and i ber length on the mechanical
properties of bamboo-reinforced starch-based resin composites. Both tensile and l ex-
ural strengths of bamboo biocomposites were strongly af ected by i ber aspect ratio
and i ber content. And it was shown that bamboo i bers with a small aspect ratio of 20
do not act as reinforcement but as i ller. h us, the ef ect of the i ber length on various
properties of biocomposites should be considered for developing biocomposites with
high performances [20-22].
h e objective of this study is to investigate the ef ect of kenaf i ber length on the ther-
mal and mechanical properties of nanoclay hybrid nanobiocomposites.
7.2
Experimental
7.2.1
Materials
Polypropylene (PP) i ber was supplied from Kolon Glotech Co., Ltd., Korea. h e spe-
cii c gravity and the melting point of PP i ber were 0.91 and 160-165°C, respectively.
And the tenacity and elongation of the PP i ber were 1.5-4.5 g/denier and 50-350%,
