Polymers and degradation of it.
A polymer is a large molecule composed of repeating structural units. These sub-units are typically connected by covalent chemical bonds.Mechanistic Aspects.Chlorine Induced Cracking:Photo Induced Degradation:
Published on: Mar 4, 2016
Transcripts - Polymers and degradation of it.
What are Polymers?
• A polymer is a large molecule composed of
repeating structural units. These sub-units are
• Because of the extraordinary range of
properties of polymeric materials, they play
an essential and ubiquitous role in everyday
• Polymer degradation is a change in the properties
tensile strength, colour, shape, etc.
• Polymer-based product under the influence of one
or more environmental factors such as heat, light
or chemicals such as acids, alkalis and some salts.
These changes are usually undesirable, such as
cracking and chemical disintegration of products.
Modes of Degradation
– Photo (Light Induced)
Single Step Reactions
Reaction rate is proportional to the rate of
Self propagation of the processes, once
started initiation reactions yield products
that themselves are capable of undergoing
spontaneous reactions with intact
Polymers can be degraded by solvolysis and mainly
hydrolysis to give lower molecular weight molecules.
The hydrolysis takes place in the presence of water
containing an acid or base.
Polymers are susceptible to attack by atmospheric
oxygen, especially at elevated temperatures
encountered during processing to shape.
Chlorine Induced Cracking:
• Another highly reactive gas is chlorine, which
will attack susceptible polymers such as
acetal resin and polybutylene pipe work.
• There have been many examples of such pipes
and acetal fittings failing in properties in the
US as a result of chlorine-induced cracking.
• Thermal degradation of polymers is molecular
deterioration as a result of overheating.
• It generally involves changes to the molecular
weight of the polymer and typical property
changes include reduced ductility and
embrittlement, chalking, color changes.
Graph of Weight v/s temperature
Photo Induced Degradation:
• Most polymers can be degraded by photolysis
to give lower molecular weight molecules.
• Electromagnetic waves with the energy of
visible light or higher, such as ultraviolet light,
X-rays and gamma rays are usually involved in
• Biodegradable plastics can be biologically
degraded by microorganisms to give lower
molecular weight molecules.