184
P. Madiwale et al.
The material scientists took the polyester terminology to a different horizon. The
aliphatic acids were introduced for esterification to increase the degradability of
the polyesters and thus a broad range of aliphatic polyesters were introduced and
quickly absorbed into the medical devices. The most common degradable polymers poly(glycolic acid) (PGA), poly(l-lactic acid) (PLLA) and poly(d-lactic acid)
(PDLA) are results of esterification of aliphatic glycolic acid or lactic acid. It has
found that most of biobased or biodegradable polyesters are having aliphatic nature.
Polylactic acid (PLA), polyglycolic acid (PGA), poly-ε-caprolactone (PCL), polyhydroxybutyrate (PHB), and poly(3-hydroxy valerate) are among some bio based
polyesters gained commercial potential on their potential research performance. The
most extensively studied biodegradable thermoplastic polyesters. Among these are
PHB and PLA have been widely used.
High hydrophilic nature of aliphatic polyester predominantly seen when exposed
to moderate to high water uptake on exposure to moist environment and it has
been well characterized that these chemical species are having low melting point,
glass transition temperature and possess poor hydrolytic stability leading to its poor
mechanical properties and stabilities and this is reason why these moieties are blended
with more stable polymers or some time biodegradable polymers are copolymerized
with aromatic building blocks (aromatic anhydride and acids), i.e. adipic acid, terephthalic acid, and 1,4-butane diol are monomeric entities to synthesize poly(butylene
adipate-co-terephthalate) (PBAT). It is well known that both are biodegradable,
biocompatible but having relatively high melting point (160–180 °C). It has been
observed that its applications have narrow range due to their brittleness and narrow processing window. Thus, in literature those have been blended with different
polymeric system have been reported.
The property of biodegradability which is the motivating factor for the directed
efforts towards aliphatic polyesters has many facets. The disposal of the degraded
products is related to the degrading time. Degradation times have been observed
to be in the range of several months to several years depending upon polymeric
systems and conditions. Another crucial property is the tensile strength which is
related to molecular volume, higher packing density, higher is the strength of the
polyester. Molecular weight (MW) of any polymeric system has a prime importance.
On alteration of MW it has observed that polyester possess varying mechanical
functionalities, i.e. On monitoring MW tensile strength of PLA could found in range
of 1–150 MPa. Tacticity also play a major role. Optical activity exhibited by most
of the aliphatic polyesters on virtue of an asymmetrical carbon atom in its repetitive unit, i.e., of alteration of l- and d-units leading to obtain isotactic l-PLA or
d-PLA and syndiotactic dl-PLA. These optical polymeric isomers have found to
possess different mechanical properties. It has been reported that dl-PLA is having
lesser tensile strength and Young’s modulus of order of half to one third than that
of l-PLA. To improve processing and end use application aliphatic polyesters are
mostly blended with other resins. To achieve low cost and increase biodegradability
polyesters could be blended with different starches. Unidirectional and biodegradable composite materials have been casted by employing biodegradable polyesters
P. Madiwale et al.
The material scientists took the polyester terminology to a different horizon. The
aliphatic acids were introduced for esterification to increase the degradability of
the polyesters and thus a broad range of aliphatic polyesters were introduced and
quickly absorbed into the medical devices. The most common degradable polymers poly(glycolic acid) (PGA), poly(l-lactic acid) (PLLA) and poly(d-lactic acid)
(PDLA) are results of esterification of aliphatic glycolic acid or lactic acid. It has
found that most of biobased or biodegradable polyesters are having aliphatic nature.
Polylactic acid (PLA), polyglycolic acid (PGA), poly-ε-caprolactone (PCL), polyhydroxybutyrate (PHB), and poly(3-hydroxy valerate) are among some bio based
polyesters gained commercial potential on their potential research performance. The
most extensively studied biodegradable thermoplastic polyesters. Among these are
PHB and PLA have been widely used.
High hydrophilic nature of aliphatic polyester predominantly seen when exposed
to moderate to high water uptake on exposure to moist environment and it has
been well characterized that these chemical species are having low melting point,
glass transition temperature and possess poor hydrolytic stability leading to its poor
mechanical properties and stabilities and this is reason why these moieties are blended
with more stable polymers or some time biodegradable polymers are copolymerized
with aromatic building blocks (aromatic anhydride and acids), i.e. adipic acid, terephthalic acid, and 1,4-butane diol are monomeric entities to synthesize poly(butylene
adipate-co-terephthalate) (PBAT). It is well known that both are biodegradable,
biocompatible but having relatively high melting point (160–180 °C). It has been
observed that its applications have narrow range due to their brittleness and narrow processing window. Thus, in literature those have been blended with different
polymeric system have been reported.
The property of biodegradability which is the motivating factor for the directed
efforts towards aliphatic polyesters has many facets. The disposal of the degraded
products is related to the degrading time. Degradation times have been observed
to be in the range of several months to several years depending upon polymeric
systems and conditions. Another crucial property is the tensile strength which is
related to molecular volume, higher packing density, higher is the strength of the
polyester. Molecular weight (MW) of any polymeric system has a prime importance.
On alteration of MW it has observed that polyester possess varying mechanical
functionalities, i.e. On monitoring MW tensile strength of PLA could found in range
of 1–150 MPa. Tacticity also play a major role. Optical activity exhibited by most
of the aliphatic polyesters on virtue of an asymmetrical carbon atom in its repetitive unit, i.e., of alteration of l- and d-units leading to obtain isotactic l-PLA or
d-PLA and syndiotactic dl-PLA. These optical polymeric isomers have found to
possess different mechanical properties. It has been reported that dl-PLA is having
lesser tensile strength and Young’s modulus of order of half to one third than that
of l-PLA. To improve processing and end use application aliphatic polyesters are
mostly blended with other resins. To achieve low cost and increase biodegradability
polyesters could be blended with different starches. Unidirectional and biodegradable composite materials have been casted by employing biodegradable polyesters