Page 348 - Biodegradable Polyesters

326 13 Biodegradable Polyester-Based Blends and Composites

PLA/poly(butyleneadipate-co-terephthalate) (PBAT) blends can be prepared
with varying tetrabutyl titanate (TBT) through melt-extrusion [33]. A twin-screw
extruder was used to obtain the blend. Mechanical properties, such as tensile
strength, elongation at break, toughness, and stiffness of PLA/PBAT blends can
be improved significantly by the incorporation of TBT [33].

13.4
Composites of Biodegradable Polyesters

Biodegradable composite materials are materials obtained from nature or by
synthetic methods, whose chemical bonds can be cleaved by bacteria or other
microorganisms present in the biosphere. Composites of biodegradable polyester
can be classified as composites made of polyester reinforced by carbon and glass
fibers, natural fibers, and degradable polymers.

13.4.1
Composites Reinforced with Carbon and Glass Fibers

CFRPs are strong and light fiber-reinforced polymers. Carbon fibers are a new
breed of high-strength materials. Carbon fiber contains at least 90% carbon pre-
pared by controlled pyrolysis of rayon fibers [34]. The subsistence of carbon fiber
came into use in 1879 when Edison took a patent for the fabrication of carbon
filaments used in electric lamps [35]. The composites manufactured using carbon
fiber reinforcements exhibit a range of mechanical properties suitable for many
constructional, industrial, and automobile applications.
PLA composites reinforced with carbon fibers can be manufactured using com-
pression molding [36]. These composites show improved performance under ten-
sile and bending loads. Specifically, it is feasible to enhance the strength of the
structural members even after these have been damaged [37]. The strength of
the columns can be increased by wrapping them with carbon fiber reinforced
PLA composites and the slabs could be strengthened by pasting composite strips
at their bottom face (tension face). Carbon fiber reinforced PLA composites are
widely used in medical applications [38]. For instance, composites made of PLA
reinforced with carbon fibers show various improvements in mechanical prop-
erties, such as tensile and flexural strengths [36]. These composites are used in
ligament replacement. In a specific case, the required breaking strength of liga-
ment to be replaced was 400 N. The ligament was replaced with a uniaxial car-
bon fiber PLA composite having breaking strength of 425 N [39]. Since PLA was
used as the matrix material, the prosthesis incorporated good biodegradability
property.
A commercial biodegradable polymer, PLA reinforced with phosphate glass
(PG) can be manufactured by the extrusion process followed by compression
molding [40]. To limit polymer degradation, the mixture of PLA and PG was
∘
manufactured at 205 C, with a screw rotation speed of 100 rpm and a dwelling