unit 2 Polymers and additives Flashcards
Toughness
Ability to absorb energy and deform without cracking,Absorbs the energy from the impact and is designed to split , dissipating the energy.
Examples of toughness
Helmets
Car bumper
Elasticity
Materials resistant to distortion and ability to return to its original shape
Examples of elasticity
Polyurethane(used in textiles)
Latex / rubber (used in balloons
Flexability and folding
Ability of a material to bend or folded without breaking
Examples of flexibility and folding
Flexible PVC sheets (used in laminating)
Thermoplastics
Mouldability
Ability to be shaped into a form or mould
Examples of mouldability
Thermoplastics moulded in hot or molten
Thermosets moulded in cold liquid and cured
Cut and scored
Ability to be scored cut and folded depends upon the hardness of the material
Examples of cut and scored
Acrylic hard and easily scored may chip
HDPE and HIPS are softer more flexible so will score less well but easily cut without chipping
What are the mechanical properties
Toughness
Elasticity
Mouldability
Flexability
Cut and scored
What are the physical properties
Insulation
Self finishing
Uv resistance
Melting points
Transparency and translucently
Resistant to chemical and liquid
Ability to be combined with other polymers and additives
Thermal insulation
Reduce heat transfer especially between objects and people
Examples of things with thermal insulation
Saucepan handles
Kitchen utensils
Electrical installation
A material the doesn’t allow electricity to flow freely through it
Examples of electrical insulation
Polymers
Electrical ligh fittings and sockets
Melting points
Is the temperature at which a material changes state from solid to liquid
Thermoplastics
When heated they become soft pliable and can be shaped and moulded
Thermosets
Don not melt but start to decompose and char at high temperature
UV resistance
Uv bleaches colour from polymers such as ABS commonly used in garden furniture
Also effects the polymers mechanical properties
What polymers are Resistant to chemicals
HDPE used in manufacturing bleach bottles and chemically resistant piping
What polymers are resistant to liquids
Both HDPE and PET are used in plastic water bottles.
HDPE I’d recycable and reusable
PET is recycable but should not be reused over time
Transparency
How permeable a material is to light radiation
Plasticisers
enhance flow characteristics
and enable polymers to be moulded at high temperature
Thermal antioxidants
help to prevent oxidation due to heat exposure during the manufacturing process
Synthetic polymers
produced
from finite resources such as coal gas and oil
Natural polymers
rubber and amber, which come from trees
Cracking
Process of converting large hydrocarbons into smaller ones
Thermo plastics
used in plastic long chains of molecules, tangled together
no fixed structure or pattern
generally soft and flexible with some shape memory
LDPE
flexible, but also tough
used in packaging where flexibility is required like
squeezy bottles and snap on lids, carrier bags and toys
translucent or opaque
Has excellent resistance to chemicals
HDPE
used for bottles, rigid plastic toys and bags for life
HDPE is harder than LDPE
good chemical resistance
Recyclable
PP
tough, flexible polymer with good fatigue resistance
food packaging medical equipment
resistant to chemicals and solvents
HIPS
rigid lightweight
high impact strength
food safe and commonly used for yogurt pots
ABS
hard and tough with excellent impact strength
ABS is widely used for domestic appliance casings,
helmets, car bumpers and wing mirrors
PMMA
Weather resistant chemical resistant
used in windows and aquariums
Nylon
Elastic very strong dries quick
Used in clothing seat belts
PVC
High impact strength
Used in windows cable wire insulation
Stock forms
• Sheet
• Film
• Granules
• Rod and other extruded forms
• Foam
• Powder
Elastomers
highly elastic and capable of recovering their original shape after being stretched
thermosets
irregularly coiled and cross-linked
When stretched molecules will straighten out in direction of pull
Thermoplastic elastomers
Most TEPs are known by their trade names
for example Elastron® & Riteflex®
They display similar properties to the cross linked elastomers like rubber
TEPs offer faster processing times than cross-linked elastomers
Stretching in elastomers
stretched and still return to their original shape
expand or contract due to temperature changes
be inflated and pressurised
worn to compress an injury or keep water out
Grip in elastomers
These may take the form of sleeves or handles
Over moulding is also used to create
spongy grips and textures on other
thermoplastic products torches, pens, toothbrushes
and sports bottles
Texture in elastomers
Most elastomers can have textures pressed or rolled into
them
* They can also be cast in textured moulds
Vulcanisation
process used to cure rubber
making it harder, more durable and heat resistant
• A curing agent, sulphur, is added to the latex from
the rubber tree
• When heated and pressurised, the
sulphur atoms form cross links
• Vulcanised rubber is tough
and can more easily retain its shape
Degradable
breaking down very slowly
into tiny plastic particles which do not assimilate back into the
earth but remain, pollute and can get into the food chain
Degradable
breaking down very slowly
into tiny plastic particles which do not assimilate back into the
earth but remain, pollute and can get into the food chain
Biodegradable
will break down without oxygen and
turn into carbon dioxide, water and biomass, finally
assimilating, however this can still take several years
Compostable
material breaks down under
certain specific conditions into carbon dioxide, water,
inorganic compounds and biomass
• It takes a much shorter time
and leaves no toxic residue
Oxy - degration
additive is often used in plastic carrier bags to speed up the process time it takes to break down can be ‘built in’ to the material
* First the material flakes, then,
over a few months or years,
the flakes turn to a powder
Photo-degration
can be used to temporarily block out light preventing growth
until they break down
• These are commonly used in domestic gardens
Hydro-degradable
suited to applications
that require a hygienic or leak-free
seal before exposure to water
• Laundry liquid pods
• Hospital laundry bags
Corn starch polymers
naturally derived biopolymer
commonly used in packaging
• It is food safe and resistant to fats
• It is oxy-biodegradable
• It is UV resistant
• It is printable
PotatoPak
inserted into a mould which is heated
under pressure to make a rigid shape
used for single use plastic items,
• By using an additive it can also
be expanded and made into
for packaging pellets
Biopol
can be moulded, formed and extruded and can be used as an additive to promote bio-degradation in other thermoplastics
disposable shampoo bottles, disposable
razors and in the lining of nappies
good UV resistance and doesnt dissolve in water
PLA
a synthetic bio-polymer powder
from corn starch
can be recycled
can be molded
PHA
a natural bio-polymer powder
made from mixed waste
food safe
can be molded
Lactide
Synthetic PLA based polymer
used in detergent pods
Glycotide
a synthetic PLA polymer
used for bags
also known as ecofilm
