What are Polymers?
• A polymer is a large molecule composed of
repeating structural units. These sub-units are
typically
c...
Examples:
•
•
•
•
•
•
Synthetic rubber
Bakelite
Neoprene
Nylon
PVC
Polystyrene
Polymer Degradation
• Polymer degradation is a change in the properties
tensile strength, colour, shape, etc.
• Polymer-ba...
Modes of Degradation
– Chemical
– Thermal
– Biological
– Photo (Light Induced)
Mechanistic Aspects
Single Step Reactions
Reaction rate is proportional to the rate of
initiation.
Chain Reactions
Self pr...
Chemical Degradation:
Polymers can be degraded by solvolysis and mainly
hydrolysis to give lower molecular weight molecule...
Chlorine Induced Cracking:
• Another highly reactive gas is chlorine, which
will attack susceptible polymers such as
aceta...
Thermal Degradation:
• Thermal degradation of polymers is molecular
deterioration as a result of overheating.
• It general...
Graph of Weight v/s temperature
Photo Induced Degradation:
• Most polymers can be degraded by photolysis
to give lower molecular weight molecules.
• Elect...
Biological Degradation:
• Biodegradable plastics can be biologically
degraded by microorganisms to give lower
molecular we...
of 11

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
Published in: Education      Technology      Business      
Source: www.slideshare.net


Transcripts - Polymers and degradation of it.

  • 1. What are Polymers? • A polymer is a large molecule composed of repeating structural units. These sub-units are typically connected by covalent chemical bonds. • Because of the extraordinary range of properties of polymeric materials, they play an essential and ubiquitous role in everyday life
  • 2. Examples: • • • • • • Synthetic rubber Bakelite Neoprene Nylon PVC Polystyrene
  • 3. Polymer Degradation • 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.
  • 4. Modes of Degradation – Chemical – Thermal – Biological – Photo (Light Induced)
  • 5. Mechanistic Aspects Single Step Reactions Reaction rate is proportional to the rate of initiation. Chain Reactions Self propagation of the processes, once started initiation reactions yield products that themselves are capable of undergoing spontaneous reactions with intact molecules.
  • 6. Chemical Degradation: 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.
  • 7. 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.
  • 8. Thermal Degradation: • 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.
  • 9. Graph of Weight v/s temperature
  • 10. 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 such reactions.
  • 11. Biological Degradation: • Biodegradable plastics can be biologically degraded by microorganisms to give lower molecular weight molecules.