Page 349 - Biodegradable Polyesters

13.4 Composites of Biodegradable Polyesters 327

time of 4 min, beneath a flow of nitrogen. In bulk composites, the addition
of 20 wt% PG provided higher mean storage modulus values compared to
the other compositions. The composites made of PLA and PG fibers provide
reinforcement similar to E-glass, but these composites are entirely degradable
in water to produce calcium phosphate [41]. Composites made of different fiber
architectures like nonwoven mats and unidirectional fiber tapes show improved
flexural properties, a modulus of 30 GPa and strength of 350 MPa [10].
Composites made of PCL reinforced with PG were manufactured by compres-
sion molding [42]. The reinforcement of PG to PCL resulted in an increase in the
rate of degradation, thus making it suitable for biomedical applications.

13.4.2
Composites Reinforced with Natural Fibers

Natural fibers possess a wide range of properties, not only because of their inher-
ent alignment properties but also because of the environment. In the automotive
industry, fiber quality guarantee protocols are used to provide assurance of the
quality of the fibers used by ensuring that both fiber nonuniformity and dimen-
sional unevenness among production consignments do not considerably affect the
desired mechanical properties such as strength and stiffness [43]. Essentially, vari-
ability in the properties of natural fibers influences the properties of the natural
fiber composites. In fact, variation in the fiber quality can be endorsed to numer-
ous factors, such as soil quality, field location, and fiber location on the plant,
seed density, weather conditions, crop variety, and harvest timing. In addition,
extraction processing methods, drying processes, variation in fiber cross-sectional
area, and the damage that occurred while processing will also affect the quality
of the natural fibers. Natural fiber reinforced composites have a strong poten-
tial to replace synthetic polymer based composites in various applications, for
example, automobile, packaging and construction [43–45]. It is a common prac-
tice to obtain the fibers from plants, as they have attractive specific properties,
such as their eco-friendly nature, low cost, and recyclability [46]. The most com-
monly used natural fiber reinforced polyester-based composites are discussed in
the following.
Jute is a common agro fibers having high tensile modulus and low elongation at
break [47]. The PLA composites reinforced with jute fibers can be manufactured
by the compression-molding technique. The jute/PLA composites can be better
replacements of E-glass fiber reinforced composites [48], as the specific stiffness
and strength are comparable to the respective quantities of E-glass fiber rein-
forced composites [48]. For instance, PLA composites reinforced with jute fibers
show a noteworthy enhancement in their mechanical properties. The flexural
strength and modulus of elasticity are increased by 40% and 90%, respectively.
By adapting the same molding technique, PBS can be reinforced with jute fibers.
These composites can be used in areas which require high tensile strength [49].
Jute spun yarn/PLA composites can be manufactured by the pultrusion process
[50]. The relation between the molding temperature and mechanical properties