Polymer Additives Flashcards
Materials
What is material enhancement?
A way of improving a materials property to better suit the requirements of the final product.
Normally carried out on metals, woods, and polymers.
What do lubricants do to polymers?
Make them less expensive and easier to process.
By adding wax or calcium stearate it reduces the viscosity of the polymer. Becomes less ‘sticky’- more intricate shapes can be formed.
Melting temperature is lowered, saving energy.
What do thermal antioxidants do to polymers?
Make them less expensive and easier to process.
They prevent the polymer from degrading through oxidation which happens when a polymer is exposed to heat/light/oxygen.
Stops them breaking down and loosing their strength.
What do pigments do to polymers?
Enhance their aesthetics.
These are tiny particles that are mixed into the molten polymer, which gives it colour.
What do flame retardants do polymers?
Improve its function.
Bromine, chlorine, phosphorous or metal are all flame retardants.
They reduce the likelihood of combustion or spreading fire. Important in plug sockets.
What do antistatics do to polymers?
Improve its function.
Plastics have poor conductivity so are used for insulating products. But insulating can lead to a build-up of static charge which attracts dust/dirt.
These attract moisture from the room, reducing the static charge and improve surface conductivity.
What do fillers do to polymers?
Improve its function.
1. Provides bulk, so less polymer is required. e.g. sawdust and flour.
2. improve polymer properties. e.g. mineral fillers- chalk, clay, etc. Help increase the thermal conductivity, so they will heat/cool faster, so shorter mould cycle times.
What do plasticisers do to polymers?
Improve its function.
Allow plastics to become less hard and brittle at normal temperature use. Allow polymers to be easily formed at higher temperatures.
Used in food wrap and hosepipes.
What do antioxidants do to polymers?
Prolong its life (prevents degradation)
reduces environmental deterioration from exposure to oxygen. Preventing brittleness, cracks and discolouration.
What do UV light stabilisers do to polymers?
Prolong its life (prevent degradation).
Prevents the polymer chains being broken down by sunlight, which cause discolouration, cracks and brittleness.
e.g. stadium seats, grass playing surfaces, hosepipes.
What do biodegradable plasterers do to polymers?
Encourage degradation.
Similar to plasterers used for enhanced processing. Makes it more flexible, softer and easier to break down.
What do bio-batch additives do to polymers?
Encourage degradation.
These additives can be added to reduce degradation time from hundreds of years to months…
oxy-degradable- degrade in oxygen. e.g. plastic bags (so they don’t end up in landfill)
photodegradable- degrade when exposed to UV.
hydro-degradable- degrade in water.
What does acrylic spray paint allow?
Mass customisation
manufacturers produce things in a ‘base coat’ and consumers choose their desired colour.
Much more cost effective than changing the granules.
Protects against UV and weathering.
What are over mouldings?
When a second layer of polymer is moulded over the product. Often by using TPE- a material that combines rubber and polymer. Produce areas of grip and texture.
E.g. a PP toothbrush would have TPE over moulding to provide grip on the handle.
What are the 2 methods of over moulding?
- Use 2 Injection Moulding moulds
One mould for product, other for grip areas. Grip would be injection moulded over the body. - Twin shot Injection Moulding
2 moulds in one machine. Product is moulded, mould opens slightly and rotates 180 degrees to secondary position. Closes and second injection applies the over mould.
Continuous- as one overcoat is placed, the next product is being moulded.
