Biodegradable polymers is an important chapter in CBSE class 12th Chemistry. Polymers play a significant role in our lives these days. There are different types of polymers and are used for different purposes. There are polymers that are resistant to the process of environmental degradation and are held responsible for the accumulation of polymeric solid waste materials. These solid wastes cause acute environmental problems and remain undegraded for quite a long time. With the increasing use of polymers, waste disposal of these products is also posing a serious problem.

Biodegradable polymers were discovered with the objective to control the damage caused to the environment during their disposal. Biodegradable polymers are comparatively easy to be decomposed by microorganisms. In this article, let’s learn everything about biodegradable polymers examples.

Biodegradable Polymers: Definition

Biodegradable polymers can be easily degraded by microorganisms within a reasonable period, ensuring that biodegradable polymers and their degraded products have a minimal environmental impact. These polymers are broken into small segments by enzyme-catalysed reactions, and microorganisms produce these enzymes.

Biodegradable Polymers: Formation

Inserting hydrolysable ester groups into the polymer chain is one way of making a biodegradable polymer. For example, if the following acetal is added to an alkene undergoing radical polymerisation, ester groups may be introduced into the polymer. Enzymes will break down these “weak links.”

Biodegradable Polymers: Examples

Aliphatic polyesters are an important class of biodegradable polymers because the weak links present in them are susceptible to enzyme-catalysed hydrolysis.

1. Poly-\(\rm{β}\)-hydroxybutyrate-co-\(β\)-hydroxy valerate (PHBV)

It is a copolymer of \(3\)-hydroxybutanoic acid and \(3\)-hydroxypentanoic acid with ester linkages connecting the monomer units.

Properties of PHBV

1. It is a biodegradable polymer and undergoes bacterial degradation in the environment.
2. In the synthesis of PHBV, \(3\)-hydroxybutanoic acid provides rigidity, while \(3\)-hydroxypentanoic acid gives it flexibility.

Uses: PHBV is used

1. For making orthopaedic devices
2. As speciality packing materials.
3. In controlled drug release.

2. Polyglycolic Acid (PGA)

Polyglycolic is obtained by the chain polymerization of a cyclic dimer of glycolic acid, \( {\text{HO-C}} { {\text{H}}_ {\text{2}}} {\text{COOH}}\).

3. Polylactic Acid (PLA)

Polylactic acid is obtained by polymerization of the cyclic dimer of lactic acid \(\left({{\text{HO-CH}}\left({{\text{C}} { {\text{H}}_3}} \right) {\text{COOH}}} \right)\).

4. Poly (\(\varepsilon \)-caprolactone) (PCL)

It is obtained by chain polymerization of the lactone of \(6\)-hydroxy hexanoic acid.

5. Nylon-2-Nylon-6

Nylon-\(2\)-Nylon-\(6\) is an alternating polyamide copolymer of glycine \(\left({{\text{N}} { {\text{H}}_ {\text{2}}} {\text{C}} { {\text{H}}_ {\text{2}}} {\text{COOH}}} \right)\) and aminocaproic acid \(\left({{\text{N}} { {\text{H}}_ {\text{2}}} {\text{-}} { {\left({{\text{C}} { {\text{H}}_ {\text{2}}}} \right)}_5} {\text{COOH}}} \right).\)

Biodegradable Polymers: List

Biodegradable polymers are two types; they are natural biodegradable polymers and synthetic biodegradable polymers. Various lists of biodegradable polymers are as follows:

Natural Biodegradable Polymer	Synthetic Biodegradable Polymer
Collagen	Polyglycolic acid
Chitosan	Polyorthoesters
Gelatin	Polyphosphoester
Hyaluronan	Polyanhydride
Starch	Polyester-amides
Albumin	Polyamides
Alginate	Poly(L-lactic acid)
Guar gum	Poly(caprolactone)
Carrageenan	Poly (lactic-coglycolic acid)
Wood	Poly (\(3\)-hydroxybutyric acid)
Pectins	Poly (sebacic acid)
Soya	Poly (adipic acid)
Casein	Polyposphazenes
Whey	Poly (dioxanone)

Biodegradable Polymers: Properties

The properties of biodegradable polymers are listed as follows. These properties will help students understand why it is easier to decompose biodegradable polymers.

1. Until degraded, biodegradable polymers can retain good mechanical integrity.
2. Since biodegradable polymers have extremely strong carbon backbones that are difficult to crack, degradation usually begins at the end-groups.
3. Biodegradable polymers are non-toxic.
4. Degradation rates of biodegradable polymers can be regulated.
5. Crystallinity is also lacking in biodegradable polymers because it prevents access to end groups.
6. Biodegradable polymers are hydrophilic.

Biodegradable Polymers: Benefits

There are many benefits of using biodegradable polymers. The list of benefits of using biodegradable polymers is listed as follows:

1. It is Easy to recycle biodegradable polymers: These polymers not only decompose faster when discarded but can also be easily recycled using an organic method. Recycling helps to reduce landfill waste, and the recycled bio-waste can also be used as compost or as a renewable energy source for biogas production.
2. The amount of waste generated is reduced: Biodegradable plastic degrades in a matter of months, depending on the material used to make it and the method of disposal.
3. Reduction in carbon Emission: One of the most important benefits of using biodegradable polymers to produce plastic bags is the significant reduction of carbon emissions during the production process instead of conventional plastic.
4. Greenhouse gas emissions are reduced: As the biodegradable polymer is used instead of conventional plastics, greenhouse gas emissions are reduced.
5. Reduced use of petroleum: Oil is an essential component in the production of traditional polymer. When you consider the amount of waste generated during refining and even during the extraction of oil from the earth, it is no surprise that petroleum harms the environment.
6. They consume less energy during their manufacture: Although the initial investment may be marginally higher, biodegradable plastics need less energy in the long run and require the reprocessing of fossil fuels to produce polymers.

Biodegradable Polymers: Disadvantage

Considering that these are polymers and they have a significantly negative impact on the environment, a list of disadvantages of using biodegradable polymers is listed as follows:

1. Landfills are designed to be moisture-and airtight to store potentially dangerous materials. These anaerobic conditions, which help to prevent toxic chemicals from being released from landfills, often slow down biodegradation.
2. The cost of biodegradable polymers is prohibitively expensive.
3. They are not readily available.
4. Biodegradable polymers are not good candidates for commingled plastic recycling.

Biodegradable Polymers: Uses

There are range of uses of biodegradable polymers. It is important for the students to understand the uses well. A list of uses of biodegradable polymers is mentioned as follows:

1. These are used for post-operative stitches.
2. Biodegradable polymers are often used in medical products, including tissue in growth materials, controlled drug release systems, plasma replacements, etc.
3. These are used in agricultural materials such as films and seed coatings.
4. These are also used in fast-food wrappers, personal hygiene products etc.
5. Biodegradable polymers are used in and on the soil to improve aeration and promote plant growth and help.
6. Biodegradable polymers are used in drug delivery because it is essential for the drug to be released slowly over time rather than at once and for the pill to stay safe in the bottle until it is time to take it.
7. Biodegradable polymers are used in gene therapy.
8. Biodegradable polymers are used in the biodegradable system for therapeutic agents such as an antitumor, antipsychotic, anti-inflammatory agent.

Non-biodegradable Polymers

Non-biodegradable polymers are those polymers that are cannot degraded by microorganisms. A major portion of synthetic polymers is being used as throwaway containers and packing materials.

Plastic is commonly used due to its low cost, versatility, and toughness, but most plastics are non-biodegradable. This longevity is due in part to the fact that plastic is a rare target for bacteria, making it non-biodegradable. On the other hand, Plastics can be made biodegradable by adding chemicals that break down the structure of the polymer.

Examples of non-biodegradable polymers are polyethylene, polypropylene, synthetic rubber, polyvinyl chloride, etc.

Polyethylene

Classification: Polyethylene is classified into the following classes based on density and branching.

1. High-Density Polyethylene (HDPE)
2. Low-Density Polyethylene (LDPE)
3. Medium-Density Polyethylene (MDPE)
4. Cross-linked Polyethylene (PEX)
5. Ultra-High-Molecular-Weight Polyethylene (UHMWPE)
6. Chlorinated Polyethylene (CPE)
7. Linear low-density polyethylene (LLDPE)

Polyethylene: Properties

The properties of polyethylene is listed as follows:

1. Polyethylene has low strength, hardness, and rigidity, yet it has a lot of ductilities, impact strength, and low friction.
2. Because of its low melting point compared to other thermoplastics, the commercial utility of polyethylene is restricted.
3. Polyethylene is made up of nonpolar, saturated hydrocarbons with a high molecular weight.
4. Polyethylene is an excellent electrical insulator.

Polyethylene: Disadvantages

A list of disadvantages associated with polyethylene is listed as follows:

1. Like many other plastics, the polymer takes a long time to degrade, and as a result, it can remain in landfills for decades, taking up space that we do not have.
2. Though most plastic polymers can be recycled technically, there are many different varieties to filter through, which is time-consuming and costly.
3. Incineration is another option for getting rid of polyethylene; however, it can produce dangerous gas emissions.
4. Polyethylene is mostly derived from petroleum or natural gas, both of which are limited resources.

Polyethylene: Uses

Uses of polyethylene is mention as follows:

1. Polyethylene films are used to make most commercial garbage bags, sandwich bags, and plastic packaging.
2. Polyethylene is utilised in various products, including seat covers, milk bottles, pails, pans, and plates.
3. Polyethylene is a film that is used to package food, clothing, and hardware.

Summary

From this article, we can conclude that biodegradable polymers are ecofriendly as they decompose by microorganisms. This property of biodegradable polymers makes their use in the medical, commercial and industrial fields.

Frequently Asked Questions on Biodegradable Polymers

Frequently asked questions related to biodegradable polymers is listed as follows:

Q.1. Is nylon \(6\) a biodegradable polymer?
Ans: No, because the amide bonds are very stable in Nylon \(6\), whereas Nylon-\(2\)-Nylon-\(6\) is a biodegradable polymer.

Q.2. What are the examples of biodegradable polymers?
Ans: The examples of biodegradable polymers are Poly-\(\rm{β}\)-hydroxybutyrate-co-\(\rm{β}\)-hydroxy valerate (PHBV), Polyglycolic acid (PGA), Polylactic acid (PLA), Poly (\(\varepsilon \)-caprolactone) (PCL) and Nylon-\(2\)-Nylon-\(6\).

Q.3. Why are some polymers biodegradable?
Ans: The polymers in which the carbon-carbon bonds of a chain are inert to enzyme-catalysed reaction; hence, polymers are non-biodegradable.

Q.4. Which is not a biodegradable polymer?
Ans: The polymers in which the carbon-carbon bonds of a chain are inert to enzyme-catalyzed reaction, hence such polymers are non-biodegradable.

Q.5. Which polymer is readily biodegradable?
Ans: Biodegradable polymers are degraded by microorganisms within a reasonable period, ensuring that biodegradable polymers and their degraded products have a minimal environmental impact. Poly(l-lactic acid), the most widely used bioderived polymer, is biodegradable. 

Q.6. How are biodegradable polymers made?
Ans: Inserting hydrolysable ester groups into the polymer chain is one way of making biodegradable polymer. For example, if the following acetal is added to an alkene undergoing radical polymerisation, ester groups may be introduced into the polymer. Enzymes will break down these “weak-links.”

Concept of Biodegradable and Non-biodegradable Polymers