Biodegradable Polymers

Polymers are everywhere — and therein lies the problem. Most of the polymers we use on an everyday basis are from petroleum-based products (the plastic grocery bags to the buckets in our homes) and although they’re durable in use, they’re also durable in waste. And the solution to this is biodegradable polymers!

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Biodegradable Polymer

These are those polymers which can decompose under aerobic or anaerobic conditions, as a result of the action of microorganism/enzymes. The materials develop it like starch, cellulose, and polyesters. Aliphatic polyesters are the most commonly used polymers of this type. Some examples are given as follows:-

• Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV):- It is derived by combining 3-hydroxy butanoic acid and 3-hydroxy pentanoic acid, in which monomers are cross-linked by an ester linkage. It decomposes to form carbon dioxide and water. It is brittle in nature, and it can be used in the production of drugs and manufacturing of bottles.

• Nylon 2–nylon 6:- It is a polyamide copolymerisation of glycine (H2N−CH2−COOH) and aminocaproic acid (H2N−(CH2)5−COOH).
• Polyhydroxy butyrate (PHB):- It is formed by the condensation of hydroxybutyric acid (3-hydroxy butanoic acid) molecules.

Browse more Topics under Polymers

• Classification of Polymers
• Types of Polymerisation
• Rubber
• Polymers of Commercial Importance
• Condensation Polymerisation or Step Growth Polymerisation

Non-Biodegradable Polymer

These polymers are resistant to environmental degradation thus end up to accumulate in form of waste.  These are polymers which have long chains consisting of Carbon and Hydrogen atoms. The interatomic bonding of these polymers is very strong and adamant, hence making them resistant to microbes which try to break their bonds and digest them.

All kind of plastics and synthetic fiber are non-biodegradable in nature. Some common examples of non- biodegradable polymers are:

• polyethene (PE), which is primarily used in packaging
• polystyrene (PS), which is a rigid, economical plastic, used mainly  for producing disposable plastic cutlery and dinnerware
• polycarbonate (PC) whose Transparency, excellent toughness, thermal stability make it suitable for Compact discs, riot shields, vandal proof glazing, baby feeding bottles, electrical components, safety helmets

Uses of Biodegradable Polymers

An estimated 86% of all plastic packaging is used only once before it is discarded, producing a stream of waste that persists in waterways and landfill, releases pollutants and harms wildlife.

Conventional polymers such as polyethene and polypropylene are durable in nature can persist for many years after disposal. They are appropriate when used for products which require a long lifespan (Example plastic tables and chairs), but seem inappropriate for applications in which plastics are used for short time periods and then disposed of (Example: packaging items).

Furthermore, plastics are often soiled by food and other biological substances, making physical recycling of these materials impractical and generally undesirable. In contrast, biodegradable polymers (BPs) can be disposed of in prepared bioactive environments to undergo degradation by the enzymatic actions of microorganisms (bacteria, algae and  fungi)

Their polymer chains may also be broken down by nonenzymatic processes such as chemical hydrolysis. BPs are often derived from plant processing of atmospheric CO₂. Biodegradation converts them to CO₂, CH₄, water, biomass, humic matter, and other natural substances. BPs are thus naturally recycled by biological processes

Biodegradable polymers contain polymer chains that are hydrolytically or enzymatically cleaved, resulting in, soluble degradation products. Biodegradability is particularly desired in biomedical applications, in which degradation of the polymer ensures clearance from the body and eliminates the need for retrieval or explant. Biodegradable polymers have applications in:

• Controlled/sustained release drug delivery approaches
• Tissue engineering scaffolds
• Temporary prosthetic implant

Solved Example for You

Q: The average molecular mass and mass average molecular mass of a polymer are 30,000 and 40.000 respectively. The PDI of the polymer is

1. < 1
2. > 1
3. 1
4. 0

Sol: The correct answer is “B”. Polydispersity Index (PDI) is the ratio of the mass average molecular mass to the number average molecular mass

PDI = 40000 ÷ 30000 = 1.33