Mr Harding Flashcards
what is toughness
ability to absorb energy
what is flexibility
ability to bend without deformation
what is elasticity
a materials resistance to distorted without plastic deformation
what is mouldability
the ability of a material to be shaped
what is a thermoplastic
a plastic that can be melted at a consistent melting point and reformed multiple times
what is a thermosetting plastic
a plastic that after setting cannot be re-melted and reformed
what are physical properties of polymers
-insulation
-self finishing
-uv resistance
-melting points
-transparency/translucency
-resistance to chemicals
-ability to be combined with additives
what is thermally insulating polymers
low heat transfer plastics, used in kitchen products, low cost
what are electrically insulating polymers
all plastics are non-conductive (no free electrons) and are used to insulate plug switches and such
typical melting conditions of thermoplastics
go soft and pliable under relatively low temperatures and pressures due to weak bonds, release noxious gasses
typical melting conditions of thermosetting plastics
char and burn, remain rigid, get more brittle, very high melting points and pressures
what is UV resistance
the ability to resist bleaching and brittleness under UV light
what is chemical resistance
ability to remain unaffected when exposed to different chemicals (defined by the inertness of the oils used) e.g bleach bottles
what is transparency
how permeable to light radiation it is, often comes as a film or sheet, used in windscreens
what is translucency
when the amount of light going through an object is limited making it harder for light to permeate through it
what is self finishing
when no additional surface finishing is required such as polishing or adding high gloss chemicals
what are plasticizers
an additive used to loosen the chemical bonds for easy mouldability (flow into moulds better)
what are thermoxidisers
an additive used to remove oxygen and prevent discolouration during moulding
what are stabilizers
an additive for the prevention of UV deterioration or temp increase
what are antistatic agents
additives to prevent a static charge building up on a plastics surface
what are colourants
an additive to make a plastic more aesthetically pleasing
what are fire retardants
additives to increase melting points and reduce flammability
what are bio batch materials
additives to make thermoplastics degrade into microplastics more quickly
what are the additives for performance
thermoxidants (anti-oxidants) , stabilizers
what are the additives for bio degradability
bio batch additives
what are the additives to improve performance
fire retardants , antistatic agents
what is the recyclability of a plastic
how easy it is to recover waste plastics by reprocessing them into useful products
what is the difference between thermoplastics and thermosetting polymers
their molecular structures and bond layout
what is cracking
where long chains of polymers fractionally distilled from crude oil are broken into smaller chains to be used
what is polymerisation
where hydrocarbons from cracking and distillation are chemically processed into polymers
what are the bonds for thermoplastics like
long chains randomly tangled
what are the bonds for thermosetting plastics like
organised and structured in a lattice
what is a flexible polymer
LDPE (low density polyethene)
what is a chemically resistant polymer
HDPE (high density polyethene)
what is a semi rigid and translucent polymer
PP (polypropylene)
what is an impact resistant polymer
HIPS (high impact polystyrene)
what is an abrasion resistant and insulating polymer
ABS (Acrylonitrile Butadiene Styrene)
what is a light, shatter resistant and fabbricatable polymer
PMMA (Polymethyl methacrylate)
what is a durable and impact resistant polymer
Nylon
what is a corrosion resistant and weather resistant polymer
PVC (polyvinyl chloride)
why do thermoplastics have low melting points
they have cross linked bonds that are easy to break
what is UF (urea formaldehyde)
a hard, opaque, well adhering tensely strong thermosetting resin that is organic and natural
what is MF (melamine formaldehyde)
a hard, brittle, scratch resistant, thermally stable thermosetting polymer
what is polyester resin
a common form of thermosetting resin used in fibreglasssing, it is water resistant, chemical resistant and requires a catalyst to harden
what is epoxy resin
a tough, brittle transparent, incredibly well adhering thermosetting resin used in carbon fibre and glue
what are stock forms
widely available basic forms of a polymer
what are the stock form types
-sheet
-film
-granules
-rod (and other extrusions)
-foam
-powder
what are Granules
small balls of a polymer
what are advantages to granules
-easy for processing
-easy to transport
-low energy to melt
or used in astro turfs and stuffing
what is a sheet
a flat large are of a material
advantages to sheets
can be easily cut or folded and vacuum formed
what is a film
a thin flexible layer of a material
advantages to film
can be bended and deformed easily or transported easily (e.g food wrapping)
what is foam board
a lamination of card faces sandwiching a foam core
advantages to foam board
-easy to cut, score and shape
-low melting points and high insulation
-sound absorbing
-ligthweight
-cannot be adhered with due to dissolving or melting
what is fluted polypropylene
a lightweight PP sheet with channels running though it for compressive strength
advantages of fluted PP
-cheap
-lightweight,
-compressively strong.
what is a rod / extruded form
an extrusion when polymers are melted and formed into a continuous profile
what are advantages of rods or extruded forms
-can be easily machined
-cheap to mass produce
-doesn’t need re-melting after purchase
what is foam
a polymer which has had air bubbled through it during manufacturing
advantages of foam
-insulating
-lightweight in a large volume
-can be made more or less dense depending on the amount of air
advantages of powders
-can be used for powder coating
-cheap to produce
-easy to ship
what is styrofoam
a dense expanded foam used for modelling, dense and uncompressible, made from polylactide sheet or film, bio degradable polymer
what are elastomers
polymers capable of returning to their original shape after stretching
why are elastomers often used for grips
they are impact absorbing, and will provide comfort to hold as they compress making them softer before returning to original shape
what is overmoulding
where 2 plastics (or metals) are moulded separately in the same mould
how can a plastics texture be altered
by changing the surface finish on the mould
how is natural rubber extracted
tapping rubber tree’s
what is vulcanisation
curing rubber to make it harder and durable but more brittle
what are features of natural rubber
a self finishing, mouldable natural polymer with excellent tensile strength and extreme low temp resistance
what is polybutadiene rubber
a strong synthetic rubber with high wear resistance and thermal resistance often used in car tyres
what is neoprene
a rubber which comes in open and closed cells, closed cells are used in sealants whilst open cell is used to trap water
what is silicone
a stable, non reactive, extremely heat resistant polymer
what is degradability in polymers
all polymers degrade into microplastics but it can take 1000 years or more
what are biodegradable polymers
those that decompose organically due to the presence of organisms into CO2, Water and biomass
what are the 2 categories of biodegradable polymers
1 - those made from natural sugars or plant starches such as PLA (and break down into biomass, water and CO2)
2- those manufactured using petrochemicals with additives to increase the speed of degradability into microplastics
the three main factors of biodegradability
oxygen, UV light and moisture
what is oxy degradation
where a material breaks down in the presence of oxygen, can be engineered to take more or less time. Always begins with flaking into smaller pieces
what is photo degradation
where polymers break down in the presence of UV, is often used to temporarily block out light before breaking down
what is hydro degradation
where a material dissolves in the presence of water and is often used to create tight seals before liquid exposure such as dishwasher capsules
what are corn starch polymers
a naturally derived biopolymer used in packaging and single use applications
what is potato pak
another starch based polymer that is compostable and made form spuds and is used in packaging after being heated and moulded
what is biopol (PHB)
a natural biopolymer made form bacteria that does not dissolve in water
what is PLA
a synthetic polymer fermented and synthesised from corn starch used in packaging and prining
what is PHA
a natural, compostable biopolymer powder made from mixed organic waste and fermented bacteria cultures, is water and oxygen resistant
what is lactide
a synthetic PLA based polymer that is both biodegradable and hydro degradable. used to release medicine at a consistent rate. must be sealed before use
what is glycolide
uses a PLA based polymer available in sheet or film.
