Biodegradable polymers

Biodegradable Polymers

 These are the polymers which gets decomposed by the process of

biodegradation.
 Biodegradation is defined as a process carried out by biological
systems usually fungi or bacteria wherein a poly chain is cleaved via
enzymatic activity.


Degradation Mechanisms



Enzymatic degradation



Hydrolysis
(depend on main chain structure: anhydride > ester > carbonate)

 Homogenous degradation
 Heterogenous degradation


Requirement of biodegradation

 Micro-organisms:


These micro-organisms must exist with the appropriate

biochemical machinery to synthesize enzymes specific for the target polymer
to initiate the depolymerization process.
Environment: Temperature, Pressure, Moisture, Oxygen, Type and
concentration of salts, Light etc.


Requirement of biodegradation

 Substrate:
 i) Suitable functional groups
 ii ) Hydrophilicity
 iii ) Low molecular weights
 iv ) Less crystallinity


Types of biodegradable polymers

 Natural biodegradable polymers
 Natural

rubber, collagen, lignin, poly(gamma-glutamic acid), starch,
cellulose, gelatin, silk, wool etc.

 Synthetic biodegradable polymers

 Polyvinyl alcohol, polyanhydrides, PHBV or poly-(3-Hydroxybutyrate-CO-3Hydroxyvalerate), Polycaprolactum, Polylactic acid, Polyglycolide.


Synthetic or Natural Biodegradable Polymers?
Why We Prefer Synthetic Materials:



Tailor-able properties



Predictable lot-to-lot uniformity



Free from concerns of immunogenicity



Reliable source of raw materials


Polyesters


PCL (Poly caprolactone)
It is a thermoplastic biodegradable polyester synthesized by chemical
Conversion of crude oil, followed by ring opening polymerisation.
PCL has good water, oil, solvent and chlorine resistance. This polymer is often used as an additive for resins to improve their processing
characteristics and their end use properties (e.g., impact resistance). Being compatible with a range of other materials, PCL can be
mixed with starch to lower its cost and increase biodegradability or it can be added as a polymeric plasticizer to PVC.
Polycaprolactone is also used for splinting, modeling, and as a feedstock for prototyping systems such as a RepRap, where it is used
for Fused Filament Fabrication

PolyBIOPOL RESIN noates

O
HO

O

+
OH

HO

Microbially
Catalyzed
Depolymerization

Bacteria
Catalyzed
Polymerization

O
O

OH

O
n

O

m

Polyhydroxy buterate valerate (PHBV)


Need for biopolymers

 Solid waste problems, particularly with regard to decreasing
availability of land fills

 Litter problems
 Entrapment or ingenious hazards to marine life.


Medical Applications of Biodegradable Polymers





Wound management
 Sutures
 Staples
 Clips
 Adhesives
 Surgical meshes
Orthopedic devices
 Pins
 Rods

 Screws
 Tacks
 Ligaments







Dental applications
 Guided tissue regeneration Membrane
 Void filler following tooth extraction
Cardiovascular applications
 Stents
Intestinal applications
 Anastomosis rings
Drug delivery system
Tissue engineering


Applications of biodegradable problems



The use of packaging materials produced from biopolymers (bio based polyesters) offers ecological
advantages over synthetic plastic packaging because they can be produced from renewable



PHB or poly(β-hydroxy butyrate) is used in the manufacture of shampoo bottles.



PLA or poly lactic acid: It breaks down in the environment back to lactic acid which can be metabolized
which has application in medical science such as sutures, drug delivery systems and wound clips. It has
also agricultural applications such as time release coatings for fertilizers and pesticides.


Limitations
 Biodegradable polymers are very expensive.
 They are not easily available.
 In order to store potentially hazardous materials, landfills are built to be free of
moisture and air tight. These anaerobic conditions which serve to guard against
the release of hazardous chemicals from landfills also retard biodegradation.

 Biodegradable

polymers are not suitable candidates in the recycling of

commingled plastics.