Page 347 - Biodegradable Polyesters

13.3 Blends of Biodegradable Polyesters 325

concerns seem to be an obstacle to their feasibility as supportable materials
particularly in view of air pollution, fossil fuel depletion, and nondegradable
waste deposition. In addition, the capability to recycle FRP composites is limited,
and, unlike steel and timber, structural components cannot be reused for a similar
purpose in another structure. It is now recognized that in order for composites
to be considered viable substitutes for conventional engineering materials, they
must be environmentally and economically feasible. As a result, research on
eco-friendly composites is being pursued over the past years, and efficient and
eco-friendly composites are now being manufactured and used in various fields of
applications.

13.3
Blends of Biodegradable Polyesters

Biodegradable polyesters blends are mostly used in biomedical and allied fields.
For instance, in the field of restructuring surgery, the use of prostheses made of
biocompatible and biodegradable materials has the benefit of avoiding reopera-
tion to remove the foreign element, and at the same time the prosthesis provides a
frame for the damaged tissue. To use the polymer blend for this purpose, it should
meet the requirements of properties as certified by specific regulatory bodies. The
fabrication is then tuned toward new materials obtained by copolymerization or
blending of previously known and accepted polymers. Polymers that are widely
used in biomedical applications are polyesters (polyglycolide, polylactide, and
poly(caprolactone) (PCL)) and natural polymers such as collagen. Ecological
problems regarding polymers arise from the stacking of hardly degradable plastic
materials in the environment. Although they form a limited fraction of urban
wastes, common polymeric products have serious disposal problems. Recent
investigations are directed toward the processing techniques to make synthetic
polymers biodegradable by incorporating additives and their degradation mech-
anisms, with their life cycle analysis and planning to minimize environmental
impact when at thetimeofdisposal[30].
Blending is a common and cost-effective way of obtaining the essential poly-
mer blends. The most commonly used biodegradable polyesters to blend are
poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly (hydroxyl butyrate) (PHB),
PCL, and poly(butylene succinate) (PBS). The PCL/PLA blends can be obtained
by a physical blending process called solvent casting [31],inwhich PCLand PLA
are dissolved in chloroform and then they are mixed. The blended polymers are
subjected to an extrusion process. The blend exhibits good mechanical properties
when compared to neat PCL and PLA. The PLA, poly(butylene-succinate-co-
adipate) (PBSA), and poly(butylene adipate-co-terephthalate) (PBTA) blends are
obtained using blown film extrusion [32]. The blends are prepared using a twin-
screw extruder. The polymer blend of PLA/PBSA (80/20 wt%) and PLA/PBTA of
(80/20 wt%) show improved tensile and impact strength. The use of PBTA in a
blend improves the mechanical properties [32].