This document discusses types of biodegradable polymers. It describes several categories of biodegradable polymers including starch-based polymers, cellulose-based polymers, bacterial polyesters, and synthetic biodegradable polymers. Starch-based polymers include thermoplastic starch, starch blended with synthetic aliphatic polyesters, starch blended with PBS or PBSA, and starch blended with PVOH. Cellulose-based polymers include cellulose esters and celluloid. Examples of bacterial polyesters discussed are PHA, PHB, PHB/HV, and PCL. The document also provides details on popular synthetic biodegradable polymers including PLA, PCL, PGA, P

1. Types of Biodegradable
Polymers
Dr.D.Syam Babu

2. Introduction
Rise of environmental pollution by synthetic
polymers in developing countries have reached
dangerous levels. Plastics produced from
petroleum resources are not biodegradable.
• Because they defy microbial degradation, they
end up in the landfills and damage the
environment.
• Totop that off, oil prices have increased
remarkably.

3. Classification of the biodegradable
polymers

4. Evolvement of Bio-Based Polymers

5. Bio-Based Polymers
• Bio-based polymers are materials which are
produced from renewable resources.

6. There are three principal ways to
produce bio-based polymers using
renewable resources
1. Using natural bio-based polymers with partial
modification to meet the requirements (eg,
starch)
2. Producing bio-based monomers by
fermentation/conventional chemistry
followed by polymerization (eg, PLA, PBS,
and PE)
3. Producing bio-based polymers directly by
bacteria (eg,PHAs).

7. Bio-based polymers are broadly divided into two
main categories:
1. Starch-based polymers.
2. Cellulose-based polymers.

8. Starch-Based
Polymers
Starch is primarily made up of two polysaccharides Amylose, a mostly linear α-D (1,4’ )-glucan and
branched amylopectin, having the same backbone structure as amylose but with many α-1,6’ -linked
branch points as shown in Fig
The starch chains has a lot hydroxyl groups, two secondary hydroxyl groups at C-2 and C-3 of each
glucose residue, as well as one primary hydroxyl group at C-6 when it is not linked. The available hydroxyl
groups on the starch chains can be oxidized and reduced, and can help in the formation of hydrogen
bonds, ethers, and esters
Starch comprises of 10-20%
amylose and 80-90%
amylopectin depending on the
source

9. Characteristics of starch-based
polymers
Some of the market drivers of starch-based polymers are:
• Lower cost materials than some other types of
biodegradable polymers such as synthetic co-
polyesters and PLA because of relatively cheap
agricultural feedstock and simpler manufacturing
process.
• Environmental-friendly than synthetic biopolymers;
• Starch blends have better physical and mechanical
properties than pure plant based polymers.

10. Starch-based polymers are used in
• Applications which are used in natural
environment such as agricultural and fishery
materials.
• Applications where reuse of the product is
difficult and composting organic waste is
effective.
• Applications with specific features, where
functionality and performance can also be
completely separated from the main function.

11. Starch-based polymers are typically
classified into four types:
1. Thermoplastic starch (TPS)
2. Starchsynthetic aliphatic polyester blends
3. StarchPBS/PBSA polyester blends
4. StarchPVOH blend

12. 1. Thermoplastic Starch
TPS is similar to other polymers with
linear and branched structures, molar mass, glass
transition temperature, crystallinity, and melting
temperature.
However, in the presence of a plasticizer such as
water, glycerin, sorbitol high temperatures
(9001800C) and shearing, it melts and fluidizes,
enabling its use in injection, extrusion, and blowing
equipment such as those for synthetic plastics.

16. 2. Starch Synthetic Aliphatic Polyester
Blends
• High-quality sheets and films for packaging are
often made from blends of biodegradable
synthetic aliphatic polyesters and starch.
• It is typical that approximately 50% of synthetic
polyester is replaced with natural polymers, such
as starch.
• Polyesters are also modified by incorporating
different functional groups such as hydroxy,
amine, and carbonyl that are capable of reacting
with natural starch polymers.

17. • When starch is blended with degradable polyesters
such as PCL, the resulting blend is fully biodegradable.
• This has become focus of biodegradable polymer
development.
• Typically, up to 45% of starch is blended with
degradable PCL. Although, the blend is fully
biodegradable, it is not strong enough for most
applications. The melting temperature is relatively low
around 600C and it gets soft at temperatures above
400C.
• Because of these drawbacks, starch PCL has limited
applications.

18. 3. StarchPBS/PBSA Polyester Blends
• One of the major starch-based synthetic aliphatic
polyester blends are starch PBS/PBSA polyester
blends. PBS and polybutylene succinate adi pate
(PBSA) are synthesized from 1,4-butanediol and
succinic and/or adipic acid at 21502250C under high
vacuum.
• The resulting average molecular weight of 40 kg/mol is
not sufficient. In order to increase molecular weight to
the desired level, a small amount of unsaturated
carboxylic acid is added under addition polymerization
initiated by peroxides.

19. • StarchPBS/PBSA blends disintegrate in
compost after 6 weeks.
• Some of their applications includes films for
compostable trash bags, paper lamination,
magnetic cards, sheets for thermoforming,
extrusion forming, monofilament for fishing
lines, woven nets, and ropes.

20. 4. Starch PVOH Blends
• Blending starch with biodegradable polyester
results in phase separation and poor interfacial
properties.
• Because PVOH degrades at high temperature
when processed by melt processing, starch PVOH
blend uses solution casting to produce films.
However, low efficiency and high processing cost
makes solution casting economically not viable
and hence not the process of choice.

21. • Mechanical properties of starch PVOH blends
are directly impacted by the amount of the
plasticizers added. Higher concentration of
plasti cizer drastically improves mechanical
properties and reduces waterabsorbance.
• In the case of citric acid, mechanical
properties such as tensile strength and
elongation at break are improved drastically
with increase in the citric acid concentration.

22. Cellulose-Based Polymers
Cellulose is a natural polymer made from long chains
that are linked together by smaller molecules. These
links in the cellulose chains consists of β-D-glucose.
These sugar units are linked when water is eliminated
by combining the H and hydroxyl group

23. There are two major cellulose-based polymers
that are commonly
used:
1. Cellulose esters
2. Celluloid

24. 1. Cellulose Esters
Cellulose esters are part of a large family of cellulose
derivatives that have found use in pharmaceutical and other
applications.
Cellulose ester is divided into two categories
1.1. Enteric
1.2. Nonenteric
Enteric esters are those which are relatively insoluble in acid
solutions but soluble in mildly acidic to slightly alkaline
solutions such as cellulose acetate phthalate (CAP).
Nonenteric esters are not dependent on pH solubility
characteristics. They are mostly insoluble in water with the
exception of cellulose acetates (CAs) with low level of acetyl

25. Ester/Cellulose ester
• Acid catalysis of an acid and alcohol also
known as Fischer esterification process is the
most important method for preparing an
ester.

28. 1.1.1.Cellulose Acetate (CA)
CA is the first organic ester of cellulosic family.
CA is prepared by mixing cellulose with acetic
anhydride using acetic acid as solvent and
sulfuric acid as catalyst. Sulfuric acid reacts with
acetic anhydride to form acetylsulfuric acid.
During the acetylation process, both sulfuric
acid and acetylsulfuric acid react with cellulose
to form cellulose sulfate acid ester.

31. 1.1.2. Cellulose-Acetate Propionate (CAP)
CAP was originally developed by the Celanese
Plastics Company in 1931. Similar to other
acetates, it is made with the addition of
propionic acid (CH3CH2COOH) in place of acetic
anhydride

32. Uses
• Plastic grade CAP has an acetyl content in the
range of 1.5 to 7 wt% and a propionyl content
of about 39 to 42 wt%.
• Because of its high transparency, low-level
light scattering, and good impact resistance,
CAP is used in high-quality frames for sun
glasses, personal protective equipment, and
sport goggles.

33. 1.1.3.Cellulose-Acetate Butyrate
Hercules Powder Company and Eastman
Chemical jointly developed CAB during the mid-
1930s.
CAB is produced when cellulose is reacted with a
mixture of sulfuric and acetic acids followed by
esterification process. During the esterification
process cellulose is reacted with butyric acid and
acetic anhydrate.

34. • This reaction is similar to the ones used in producing CA
except that butyrate is also used. The end product has
acetyl groups (CH3CO) and butyl groups
(CH3CH2CH2CH) in the repeating cellulose unit.

35. Use
• CAB has acetyl content in the range of 13-15 wt%, a
butyryl content of 34-39 wt%, and a free hydroxyl
group of 1-2 wt%. CAB products have good
dimensional stability among family of other acetates.
• They have excellent toughness, moisture resistance,
and are available in fine colors.
• They are typical extruded and have found their use for
automobile steering wheels, knobs, tool handles,
packaging blisters, illuminated advertising signs,
machine hoods, lamp covers, and dome lights

36. 1.2.Celluloid
It all started when cellulose was treated with
strong nitric acid to form nitrocellulose, which
found some use as an explosive.

39. • Once cellulose nitrate is synthesized, it is then
mixed with camphor; a resin from the
evergreen Cinnamomum camphora.

40. Some of the factors that can contribute to
degradation of celluloid include
• The purity of ingredient materials;
• The rinsing and drying processes, which may
leave agents catalyzing degradation in the
finished materials;
• The kneading process.

41. Bacterial Polyesters
• Among all biodegradable polymers, polyesters are
considered as a primary choice because of their
hydrolyzable ester bonds. The polyesters are
classified into two types: aliphatic polyesters and
aromatic polyesters.

42. Some of the important characteristics of bacterial
polyesters are as follows
1. They are water-resistant, and products made of
the polyesters are water-tight.
2. The material can be processed by injection and
blow molding.
3. Polyesters are not flexible and tend to become
brittle.
4. Polyesters tend to lose their vapor barrier
properties.

43. Some of the bacterial polyesters are:
1. Polyhydroxyalkanoate (PHA)
2. Polyhydroxybutyrate (PHB)
3. Poly(hydroxy- butyrate-hydroxyvalerate)
(PHB/HV)
4. Poly(ε-caprolactone) (PCL).

44. 1. Polyhydroxyalkanoates
PHAs are a family of intracellular biopolymers
produced by bacterial fermentation of sugar or
lipids. They are produced by numerous bacteria
to store carbon and energy.

46. Properties

47. Synthesis of PHA

48. Systems for PHA synthesis

49. Use

50. 2. Polyhydroxybutyrate
PHB is the second member of the bacterial
polyesters. It was synthesized from bacteria
Bacillus magaterium by Lemoigne in 1925.
PHBs are the class that is of interest for bio-
derived and biodegradable plastics. The
generalized chemical structure of PHB is:

55. 4. Synthetic Biodegradable Polymers

56. 1. Poly(lactic acid) (PLA)
PLA belongs to the family of aliphatic polyesters that are
derived from renewable sources, mainly starch and sugar.
It is a rigid thermo plastic polymer that can be
semicrystalline or amorphous, depending on the
stereochemistry of the polymer backbone.
Lactic acid (2-hydroxyl propionic acid), the building block
of PLA can exist either in D- or L-enantiomers.
The properties of PLA will depend on the proportion of
the enantiomers allowing production of PLA with wide
range of properties to match with the performance
requirements.

61. Thermal Degradation
PLA tends to undergo thermal degradation in the molten state.
Most of this form of degradation is related to processing of PLA
which include process temperatures and the residence time in
the extruder. Other factors that can contribute to thermal
degradation of PLA include
• Hydrolysis by trace amounts of water;
• Depolymerization;
• Oxidative, random main-chain scission;
• Intermolecular transesterification to monomer and oligomeric
esters;
• Intramolecular transesterification resulting in formation of
monomer and oligomer lactides of low molecular weight.

63. 2. Poly(ε-caprolactone)
Poly(ε-caprolactone) PCL is a semicrystalline,
biodegradable polymer with melting
temperature (Tm) of B 600C and a glass
transition temperature (Tg) of B2 600C.

64. Synthesis
PCL is synthesized by the ring opening
polymerization of the cyclic monomer ε-
caprolactone.

65. hydrolytic cleavage

66. 3. Poly(glycolide) or Poly(glycolic acid)
Poly(glycolide) also known as PGA is a highly
crystalline, biodegradable polymer having a
melting point of 2250C and a glass transition
temperature of 350C. T

68. 4. Poly(p-dioxanone)
• PDS is prepared by the ring opening
polymerization of p-dioxanone.

71. 5. Bio-Derived Polyethylene
Ethanol produced by fermentation from
renewable resources can be used as a bio-fuel
but also as a raw material for Bio-PE production.
LDPE—Low-density polyethylene
HDPE—High-density polyethylene