Polymer Processes Flashcards
what 6 polymer uses a mould/former?
vacuum forming
thermoforming
injection moulding
blow moulding
rotational moulding
compression moulding
what is vacuum forming?
mould in placed into a former and a plastic sheet is then heated onto of the mould. once the plastic sheet is hot enough, the mould rises into the sheet of which provides a very loose coat. the air is then sucked put with a vacuum which suck the sheet tightly around the mould as it hardens. the rubber seal must be in place correctly in order to ensure a vacuum
what is thermoforming?
a plastic sheet is heated and then the air is sucked out, pulling the plastic into the mould in order to change its shape. a positive mould is then placed on top to fully change the plastics shape as it hardens.
what is line bending?
a line of plastic is heated to soften it. once this is done a jig is used to order to then the plastic to the correct degree with the use of G-clamps aswell
what is injection moulding?
polymer pellets are funnelled through to a chamber of which an Archimedes screw is used with a motor causing the polymer to travel down a heating chamber. this is heated with heating elements which cause the plastics to melt. at the end of the chamber it is fed through a sprue and into a cavity within the two parted mould. the sprue is then closed and the plastic is water cooled as it hardens. it is remover when sprue pins are removed allowing for the two part mould to release the polymer inside. the characteristics of injection moulding is detail, complex shapes, sprue marks and shut lines
what is lamination layup?
lamination layup is the repeated layers of GRP and then epoxy resin. GRP is placed down and after the resin is onto it is then rolled with a roller over the top in order to flatten out. this process is repeated until the desired strength is reached. it will have a release agent at the bottom, then the mat with the resin and then rolled
what is blow moulding?
the mould is opened into its two halves as a hollow tube (garrison) is heated above. the garrison is lowered into the mould and then the mould is clamped shut leaving only a hole for the air hose. air is forced into the mould at high pressure causing the garrison to stretch into the sides of the moulds and hardens into the shape of it. this forms the shape of the bottle for example
what is rotational moulding?
liquid polymer is poured into the mould and then it is shut.the mould then spins which coats the inside with the molten plastic. it hardens like this and the plastic product is taken out of the mould
what is extrusion?
Extrusion is similar to injection moulding up until the end where instead of going through a sprue into a cavity, it goes though a die and is then water cooled into its new shape which produces continuous shapes like tubing for example
what is compression moulding?
takes a blob of heated polymer and a punch then forces it into a mould of which shape it then takes. it hardens in this new form and the product is made
what 3 polymer processes don’t use a mould/former?
lamination
line bending
extrusion
calendaring
