1.13 Enhancement of Materials Flashcards
Define material enhancement
A way of improving a material’s properties to better suit the requirement of the final product
Polymer Enhancement
State the reason for adding lubricants
Adding wax or calcium stearate reduces the viscosity of the molten polymer, making it less ‘sticky’ and allowing more intricate shapes to be formed.
Lubricants also allow the moulding temperature to be lowered, saving energy
Polymer Enhancement
State the reason for adding thermal antioxidants
Prevent the polymer oxidising or discolouring due to excessive heat during processing.
Polymer Enhancement
State the reason for adding pigments
Tiny particles that are mixed into the polymer in its molten state to give colour to the final processed product
Polymer Enhancement
State the reason for adding antistatics
Reduce the likelihood of the polymer building up a static charge
Polymer Enhancement
State the reason for adding flame retardants
Reduce the likelihood of combustion or the spread of fire (care engine components) or potential electrical fires such as plug sockets.
Polymer Enhancement
State the reason for adding plasticiser
Allow plastics to become less hard and brittle at normal temperature use, e.g. added to LDPE food wrap, allowing the wrap to be stretched over the food product.
Plasticisers also help in processing because they allow polymers to be easily formed at higher temperatures
Polymer Enhancement
State the reason for adding fillers
Sawdust and wood flour provide bulk to the product, meaning that less polymer is required.
Mineral fillers such as chalk, clay and calcium carbonate help increase the thermal conductivity of the polymer, meaning it will heat up and cool down more quickly, which gives shorter mould cycle times.
Polymer Enhancement
State the reason for adding biodegradable plasticisers
These make the polymer more flexible, softer and easier to break down, which means faster degradation time.
Polymer Enhancement
State the reason for adding bio-batch additives
Oxy-degradable, photodegradable and hydro-degradable additives help reduce the degradable time from hundreds of years to a few years or even months.
Polymer Enhancement
State the reason for adding antioxidants
Help reduce the environment of the polymer from exposure to oxygen in the air
Also help prevent increased brittleness, surface cracks and pigment discolouration. Often used in polymer garden furniture.
Polymer Enhancement
State the reason for adding UV light stabilisers
Prevent the polymer chains being broken down by sunlight. UV attack causes colour loss and brittleness. Used in outdoor toys and play equipment, garden furniture, sports stadium seats and synthetic grass playing surfaces.
Wood Enhancement
State the use of resins and laminations
Used in engineered wood (e.g. manufacture boards) to enchance the properties of the useable parts of trees such as sawdust, wood chips and fibres.
Chipboard is made from compressing wood chip with a resin (urea formaldehydel).
Wood Enhancement
State the use of resins with fire retardants
Resin is impregnated with fire-retardant cladding (e.g. for indoor flooring).
Wood Enhancement
State the use of laminations
Veneers such as natural wood are laminated on to the board surface to enhance aesthetics.
Wood Enhancement
State the use of preservatives
Protect wood (especially for outdoor use) form fungal and insect attack.
Wood can be pre-treated with a copper-based preservative, which penetrates the wood to protect the whole plank.
Copper has excellent fungicidal properties.
Wood Enhancement
State the use of pigments
Added to the preservative to give different coloured shades to enhance the aesthetics, e.g. outdoor decking.
Can also be used on cheaper softwoods to make them look like hardwoods.
Wood Enhancement
State the use of fire-retardant preservatives
Used to pressure treat wood for roof joists, cladding etc. and exhibition stands.
Wood can also be treated to make it harder and more resistant in high-wear situations such as flooring.
Wood Enhancement
State the use of modified natural polysaccharides
Wood is impregnated to cure within wood cell structure. Results in increased hardness, toughness and stability (often added to hardwood floor panels)
Wood Enhancement
State the use of structural composite lumber (SCL) and laminated veneer lumber (LVL)
Made by layering strands (SCL) or veneers (LVL) of wood with resins such as urea formaldehyde, pressing and heat curing them to produce a stable wood billet.
SCL and LVL are less prone to defects such as warping, splitting or shrinking.
Used in structural applications including beams, joists and rafters.
Metal Enhancement
Define work hardening
Improves tensile strength and hardness in the localised area when a metal is cold worked.
Metal Enhancement
Define annealing
Heating work-hardened metal and very slowly cooling it, making it easier to work (less brittle and more ductile).
Metal Enhancement
Define case hardening
Hardens the surface of steel with less than 0.4 per cent carbon content.
Metal Enhancement
Define carburising
Changes the chemical composition of the surface of low carbon steel so it absorbs more carbon and increases surface hardness.
Metal Enhancement
Define quenching
Rapid cooling of a heat-treated metal.
Metal Enhancement
Define Hardening and tempering
Heating medium and high carbon steels to a given temperature, rapidly cooling via quenching and then heating to a set temperature to remove the excess to hardness.
Metal Enhancement
Define tempering colour
The colour seen on metal that indicates the temperature at which brittleness is removed
