To recognize common thermoplastics and thermosets.
Distinguish typical properties of common plastics with those of metals and ceramics; and understand the relationship between the mechanical, chemical, and physical properties of the plastics and their molecular, micro and macro structures.
Demonstrate deep understanding of the major manufacturing processes of plastics and analyze the advantages and disadvantages of those processes for making specific parts.
These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling.These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. Some common thermoplastics are polythene, polystyrene, polyvinyls, etc.
A thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently.
Most thermoplastics are high-molecular-weight polymers whose chains associate through weak Van der Waals forces (polyethylene); stronger dipole-dipole interactions and hydrogen bonding (Nylon).
These polymers are cross linked or heavily branched molecules,which on heating undergo extensive cross linking in moulds and again become infusible. These cannot be reused. Some common examples are bakelite, urea-formaldelyde resins, etc.
Thermoplastic polymers differ from thermosetting polymers (Bakelite, vulcanized rubber) since thermoplastics can be remelted and remolded.
Thermosetting plastics when heated, will chemically decompose, so they cannot be recycled. Yet, once a thermoset is cured it tends to be stronger than a thermoplastic.
Typically, linear polymers with minor branched structures (and flexible chains) are thermoplastics. The networked structures are thermosets.
Thermoplastic materials are those materials which:
The word ‘polymer’ is meant for a material made from _______________.
One of the characteristic properties of polymer material _____________ . (ISRO Scientist ME 2013)
These polymers cannot be recycled:
In general, strongest polymer group is: ______________.
Strong covalent bonds exists between polymer chains in ______________.