BIODEGRADABLE

POLYMERS

By :Madhuri Phute

Biodegradation

Biodegradation is the process of converting

polymer material into harmless, simple, gaseous products

by the action of enzymes, micro-organisms and water.

Biodegradable PolymerBiodegradable polymers degrade as a result of

natural biological processes, eliminating the need to create a disposal system which can cause harm to our environment.

INTRODUCTION

NEED FOR BIODEGRADABLE

POLYMERS• Polymers have become an essential part of our daily

life.

• Having its numerous advantages, it finds it use in

every field.

• But these polymer products account for approx. 150

million tons of non biodegradable waste every year.

• Such large amounts of waste leads to various

problems, not to mention, a general lack of

cleanliness in the neighbourhood.

• Inert

• Permeability

• Non-toxicity

• Bio-compatibility

• Tensile strength

• Mechanical strength

• Controlled rate of degradation

Characteristics Of

Biodegradable Polymers

BIODEGRADATION

ENZYMATIC

DEGRADATIONCOMBINATIONHYDROLYSIS

BULK EROSION SURFACE EROSION

Mechanism Of Biodegradable Polymers

ENZYMATIC DEGRADATION

Enzymatic degradation takes place with the

help of various enzymes.

The type of enzymes used for degradation

depends upon the type of polymer:

• Fungi – ‘ Fusarium Moniliformae’

• Yeast- ‘Cryptococcus

• Enzymes from moulds such as ‘Penicillium’

POLYMER DEGRADATION AND

EROSION

Degradation ----- Chain Cleavage

Erosion ------- Loss of Mass

1. Bulk Erosion

2. Surface Erosion

Degradation in two Phases

1.-Water penetration (Rate Determining)

-Attacking Chemical bonds

-Shorter water soluble fragments

2.-Rapid loss of polymer

-Enzymatic attack

-Solubilisation

EROSION

Type I Erosion :

• Evident with water soluble polymers cross linked to form three dimensional

network.

• Cross linking still intact.

• Network insoluble.

• Swelling.

• Solubilisation by cleavage of water soluble backbone or crosslinking

Type II Erosion :

• Polymers first are water insoluble but converted to water soluble by reaction

with pendant group.

Type III Erosion :

• Polymers with high molecular weight are broken down and transformed to

smaller water soluble molecules.

POLYMER DEGRADATION POLYMER EROSION

CHEMICAL STRUCTURE

(a) Functional Group

(b) Hydrophobicity

MORPHOLOGY

(a) Tensile strength

(b) Branching

PARTICLE SIZE

Larger the particle size slower the degradation

process.

FACTORS AFFECTING

BIODEGRADATION

BIODEGRADABLE

POLYMERS

• Biopol

(Polyhydroxybutarate-hydroxyvalerate)

• Polycaprolactone

• Polylactic Acids

• Polyglycolic Acids

• Polydioxane

BIOPOL

BIOPOL is a copolymer of

3-hydroxy butyric acid and

3-hydroxy valeric acid.

PRODUCTION :

It is produced by

fermentation of

glucose by

Acaligenes

eutrophus

species.

POLYHYDROXYBUTARATE-

HYDROXYVALERATE

(PHB-HV)• It is a type of

Biopolymer.

• Molecular Formula:

C27H42O12

• Monomer Weight:

558.62 amu

Properties of Biopol :

• Water insoluble and relatively resistant to hydrolytic degradation.

Good oxygen permeability.

• Good ultra-violet resistance but poor resistance to acids and bases.

• Soluble in chloroform and other chlorinated hydrocarbons.

• Biocompatible and hence is suitable for medical applications.

• Melting point 175 C., and glass transition temperature 2 C.

• Tensile strength is 40 MPa close to that of polypropylene.

• Sinks in water (while polypropylene floats), facilitating its anaerobic

biodegradation in sediments.

• Nontoxic.

• Less 'sticky' when melted, making it a potentially good material for

clothing in the future

POLYCAPROLACTONEPolycaprolactone (PCL) is a biodegradable polyester.

Preparation of Polycaprolactone:

Properties Of Polycaprolactone:

• It has a low melting point of around 60 C.

• It has a glass transition temperature of about −60 C.

Uses Of Polycaprolactone:

• The most common use of polycaprolactone is in the

manufacture of speciality polyurethanes.

• Polycaprolactones impart good water, oil, solvent and

chlorine resistance to the polyurethane produced.

• This polymer is often used as an additive for resins to

improve their processing characteristics and their end

use properties.

• 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.

Degradation Of Polycaprolactone:

• PCL is degraded by hydrolysis of its ester

linkages in physiological conditions (such as in

the human body).

• It has therefore received a great deal of

attention for use as an implantable biomaterial.

• In particular it is especially interesting for the

preparation of long term implantable devices,

owing to its degradation which is even slower

than that of polylactide (or polylactic acid).

POLYLACTIC ACID

• Polylactic acid or polylactide

(PLA) is a thermoplastic

aliphatic polyester derived from

renewable resources, such as

corn starch, tapioca products

(roots, chips or starch) or

sugarcane.

• It can biodegrade under

certain conditions, such as the

presence of oxygen, and is

difficult to recycle.

• The name "polylactic acid" does not comply with IUPAC standard

nomenclature, and is potentially ambiguous or

confusing, because PLA is not a polyacid (polyelectrolyte), but

rather a polyester

Formation of Polylactic Acids:

Bacterial fermentation is used to produce

lactic acid from corn starch or cane sugar.

Uses of Polylactic Acids:

Mulch film made of PLA-blend

bio-flex

Biodegradable PLA cups

in use at an eatery

Due to PLA's relatively low

glass transition

temperature, PLA cups

cannot hold hot liquids.

However, much research is

devoted to developing a heat

resistant PLA.

POLYGLYCOLIC ACID• Polyglycolide or

Polyglycolic acid (PGA) is a

biodegradable, thermoplastic

polymer and the simplest linear,

aliphatic polyester.

• It is a tough fibre-forming

polymer. Due to its hydrolytic

instability its use has been

limited.

• It has a glass transition

temperature between 35-40 C.

• Its melting point is in the range

of 225-230 C.

• It also exhibits an

elevated degree of

crystallinity, around 45-

55%, thus resulting in

insolubility in water.

Preparation of Polyglycolic Acids:

Polyglycolide can be obtained through several different

processes starting with different materials:

• Polycondensation of glycolic acid

• Ring-opening polymerization of glycolide

• Solid-state polycondensation of halogenoacetates

Degradation of Polyglycolic Acids:• Polyglycolide has hydrolytic instability due to the presence of the

ester linkage in its backbone.

• The degradation process is erosive and appears to take place in

two steps during which the polymer is converted back to its

monomer glycolic acid:

1. First water diffuses into the amorphous (non-crystalline)

regions of the polymer matrix, cleaving the ester bonds.

2. Second step starts after the amorphous regions have been

eroded, leaving the crystalline portion of the polymer susceptible to

hydrolytic attack. When the crystalline regions collapse, the polymer

chain dissolves.

• When exposed to physiological conditions, polyglycolide is

degraded by hydrolysis, and broken down by certain enzymes.

• The degradation product, glycolic acid, is nontoxic.

• Studies undergone using polyglycolide have shown that the

material loses half of its strength after two weeks and 100% after

four weeks. The polymer is completely resorbed by the organism in

a time frame of four to six months.

POLY ESTERS

POLY PHOSPHO ESTERS

POLY ANHYDRIDES

POLY OLEFINS

POLY AMIDES

Biodegradable Polymers

For Controlled Drug Delivery

NATURAL POLYMERSThese are the polymers obtained from natural resources, and

are generally non-toxic.

NATURAL POLYMERS

PROTEINS Polysaccharides

Ex: COLLAGEN

ALBUMIN

FIBRIN

Ex : DEXTRAN

CHITOSAN

STARCH

ADVANTAGES : 1) Readily & Abundantly Available.

2) Comparatively Inexpensive.

3) Non toxic products.

4) Can be modified to get semi synthetic

forms.

• S. P. Vyas, Roop K. Khar; Controlled Drug Delivery –Concepts And Advances; First Edition, Reprint 2010; Vallabh Prakashan; Page No. 97 – 154

• N. K. Jain; Advances in Controlled & Novel Drug Delivery; First Edition, Reprint 2003; CBS Publishers & Distributors; pg. no. 1 – 17

• Mark Chasin, Robert Langer; Biodegradable Polymers as Drug Delivery Systems; First Indian Edition, Reprint 2008; Marcel Dekker.

• PowerPoint presentation by Mr. Shrikant Sharma.

• Internet sites:

– www.wikipedia.com

– www.athurstream.com

– www.slideworld.com

– www.google.com

Reference