INTRODUCTIONBiodegradation Biodegradation is the process of convertingpolymer material into harmless, simple, gaseous productsby the action of enzymes, micro-organisms and water.Biodegradable Polymer Biodegradable polymers degrade as a result ofnatural biological processes, eliminating the need tocreate a disposal system which can cause harm to ourenvironment.
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.
Characteristics Of Biodegradable Polymers• Inert• Permeability• Non-toxicity• Bio-compatibility• Tensile strength• Mechanical strength• Controlled rate of degradation
ENZYMATIC DEGRADATION Enzymatic degradation takes place with thehelp of various enzymes. The type of enzymes used for degradationdepends upon the type of polymer:• Fungi – ‘ Fusarium Moniliformae’• Yeast- ‘Cryptococcus• Enzymes from moulds such as ‘Penicillium’
POLYMER DEGRADATION AND EROSIONDegradation ----- Chain CleavageErosion ------- Loss of Mass1. Bulk Erosion2. Surface Erosion Degradation in two Phases1.-Water penetration (Rate Determining) 2.-Rapid loss of polymer -Attacking Chemical bonds -Enzymatic attack -Shorter water soluble fragments -Solubilisation
EROSIONType 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 crosslinkingType 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.
BIOPOL BIOPOL is a copolymer of 3-hydroxy butyric acid and 3-hydroxy valeric acid.PRODUCTION : It is produced byfermentation ofglucose byAcaligeneseutrophusspecies.
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 producelactic acid from corn starch or cane sugar.
Uses of Polylactic Acids:Mulch film made of PLA-blend Biodegradable PLA cupsbio-flex in use at an eatery Due to PLAs 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 also exhibits an• It has a glass transition elevated degree of temperature between 35-40 C. crystallinity, around 45-• Its melting point is in the range 55%, thus resulting in of 225-230 C. insolubility in water.
Preparation of Polyglycolic Acids:Polyglycolide can be obtained through several differentprocesses 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.
NATURAL POLYMERSThese are the polymers obtained from natural resources, and are generally non-toxic. NATURAL POLYMERS PROTEINS Polysaccharides Ex: COLLAGEN Ex : DEXTRAN ALBUMIN CHITOSAN FIBRIN STARCHADVANTAGES : 1) Readily & Abundantly Available. 2) Comparatively Inexpensive. 3) Non toxic products. 4) Can be modified to get semi synthetic forms.
Reference• 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