Biodegradable Polymers - Definition, Examples, Uses, Non-Biodegradable Polymer and its Example, Practice Problems and FAQ

Solid waste dumping is becoming a serious problem for our environment as it results in pollution but there is some form of biodegradable polymers that undergoes degradation by microorganism and do not accumulate as waste causing less pollution and harm to our environment.

Table of Contents

Definition of Biodegradable polymer
Example of biodegradable polymers
Properties of biodegradable polymer
Uses of biodegradable polymer
Non-biodegradable polymers and its example
Practice problems
Frequently asked questions(FAQs)

Definition of Biodegradable polymers

It is those type of polymers which get decomposed under either an aerobic or anaerobic condition with the help of microorganism/enzymes into simpler units and are called biodegradable polymers.

Examples- starch, cellulose, proteins, DNA, RNA etc. The functional groups of biodegradable polymers are comparable to those of biopolymers such as proteins and carbohydrates.

Example of biodegradable polymers

1). Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV)

It is obtained by the copolymerisation of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid.
The monomers are connected via ester linkages.
PHBV undergoes bacterial degradation in the environment.
The properties of PHBV depend on the ratio of the monomers. 3-Hydroxybutanoic acid gives stiffness while 3-hydroxypentanoic acid gives flexibility to the polymer.

2). Nylon-2-nylon-6 : It is a polyamide copolymer of aminocaproic acid (H₂N - (CH₂)₅- COOH) and glycine (H₂N - CH₂- COOH).

3). Polyhydroxybutyrate (PHB):

It is formed by the condensation of hydroxybutyric acid( 3-hydroxy butanoic acid).
It belongs to polyester class of biodegradable plastics.
It is water insoluble and relatively resistant to hydrolytic degradation.

Uses of biodegradable polymers

These polymers are well suited to make durable products like plastic chairs and bottles are to be made, but not for daily use (plastic bags) and disposables (packaging items).
Poly-β-hydroxybutyrate-co-β-hydroxy valerate is used in speciality packaging, orthopaedic equipment and controlled drug release.
A drug packed in a capsule of PHBV is released only after the degradation of the polymer. PHBV undergoes bacterial degradation in the environment.
Polyglycolic acid polylactic acid is used in postoperative stitches.
Nylon-2-nylon-6 is used in making strings of musical instruments, toothbrushes etc.

Non-biodegradable polymers and their example

It is those type of polymers which is difficult to get decomposed with the help of microorganism/enzymes into simpler units as they generally consist of a long chain of carbon and hydrogen atom due to the interatomic type of bond and are called a non-biodegradable polymer.

Examples of non-biodegradable include:

Low-density polyethene( LDPE)
High-density polyethene(HDPE)
Polytetrafluoroethylene(Teflon)

Polyethylene terephthalate(PET)

Polystyrene(PS)

Practice problems

Q1 Which of the following is the biodegradable polymer of the class polyamides?

Nylon-6,6
Nylon-6
Nylon-2-nylon-6
Nylon-5

Answer: C)

Solution: The compounds given in all the options are polyamides. Among the given polyamide polymers only Nylon-2-nylon-6 is biodegradable. It is a polyamide copolymer of amino caproic acid and glycine.

Q2. In poly-𝞫-hydroxybutyrate-co-𝞫-hydroxy valerate (PHBV), 3-hydroxybutanoic acid and 3-hydroxypentanoic acid give __________ and __________, respectively.

Flexibility, stiffness
Flexibility, temperature resistance
Stiffness, flexibility
Temperature resistance, Stiffness

Answer: C)

Solution: 3-hydroxybutanoic acid gives stiffness and 3-hydroxypentanoic acid gives flexibility in poly-𝞫-hydroxybutyrate-co-𝞫-hydroxy valerate (PHBV).

Q3 Polymers that undergo degradation and do not accumulate as waste is called ________.

Non-biodegradable polymers
Condensation polymers
Addition polymers
Biodegradable polymers

Answer: D

Solution: It is those types of polymers which get decomposed in an aerobic or anaerobic condition with the help of microorganism/enzymes into simpler units and are called biodegradable polymer.

Q4 What are some important properties of biodegradable polymers?

Answer: Some important properties of biodegradable polymers includes:

Polymer are hydrophilic in nature
Retains mechanical integrity
Polymers are generally non-toxic
Rate of degradation of polymer can be regulated

Frequently asked questions(FAQs)

Question 1. What is the difference between LDPE and HDPE polymers?
Answer: LDPE stands for Low density polyethylene formed due to polymerisation of ethene molecule in the presence of benzoyl peroxide catalyst at temperature range of 350 to 600 Kand at a high pressure 1000 to 2000 atm. Whereas, HDPE stands for High density polyethene formed due to due to polymerisation of ethene molecule in the presence of Ziegler-natta catalyst{(C₂H₅)₂Al and TiCl₄} temperature range of 333 to 343 Kand at a high pressure of 6 to 7 atm.

Question 2. What is the difference between Nylon-6 and Nylon-2-nylon-6?
Answer: Nylon-6 is polyamide(i.e. Containing amide linkage) which is obtained from strong heating of caprolactum at a temperature range of 533 K to 543 K. Whereas, Nylon-2-nylon-6 It is a polyamide copolymer of aminocaproic acid(H₂N - (CH₂)₅- COOH) and glycine (H₂N - CH₂- COOH).

Question 3. What are the disadvantages of using polyethene?
Answer: Polyethene generally take longer time for degradation and leads to emission of house gases including carbondioxide that leads to climate change and global warming during its production.

Question 4. What are the important factors responsible for degradation of biodegradable polymer?
Answer: Some common factors that affect the degradation of the biodegradable polymer include heat, light air and water but the rate of degradation of biodegradable polymer also depends on various factors like the rate of oxidation and chain scission which leads to a reduction in degree of polymerisation and molecular weight of the polymer.

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