Polymers are very large molecules made when many smaller molecules join together, end to end creating really long chains. The smaller molecules are called monomers. strong covalent bonds hold the monomers together to create a polymer.
theremosoftening polymers are made of tangled up chains of polymers. they have no crosslinks and so are held together through weak intermolecular meaning they can slide over one another as the forces between the chains are really easy to overcome.
this making it easy to melt at lower temperatures and when the polymer harden it is in a new shape. themosoftening polymers can be remoulded as many times as you want and so is easy to recycle.
thermosetting polymers have cross links between the polymer chains creating very strong intermolecular forces keeping the chains in a firm solid structure making thermosetting polymers tough,strong, hard and rigid. the cross links also make the polymer unable to melt when heated, at a certain temperature it just burns instead.