polymers 4 Flashcards
what kind of polymer is tumble blending used for?
free flowing powder/granules
what kind of polymers are mixed by stirring?
liquid polymers with low viscosity
what ways are viscous polymers like rubber mixed?
open roll mill/two roll mill
intensive mixer
twin/screw extruder
how are thermosets vs thermoplastics made into liquid?
thermoplastic: heat above glass transition temperature
thermoset: is a low viscosity liquid when mixed
how are thermoplastics vs thermosets shaped?
thermoplastic: extrusion, welding, moulding, cutting
thermoset: moulding, cutting
how are thermoplastics vs thermosets hardened after shaping?
thermoplastics: cool down
thermosets: may have to heat to cure
what are the three steps of shaping a polymer?
processing into a liquid, shaping, hardening
what are extrusion processes used for
making continuous products of constant cross section from thermoplastics or rubber compounds (either calendering or screw extruder)
what are wet/dry spinning processes used for?
creating fibres (think spinning wheel yarn)
what are bubble forming/film blowing processes used for?
making thin thermoplastic film
what is exotherm when processing polymers?
when thermosets are cured, a large amount of heat is evolved, cause vigorous reactions and large temperature rises can occur
what are the different ways polymers can be joined?
mechanical with ‘snap’ fastener devices made from mould. welding for thermoplastics. adhesive bonds, applicable to both thermoset and thermoplastic
