13 Enchantments Flashcards
Polymer enhancements
3 that help during manufacture
Lubricant
Thermal antioxidants
Plasticisers
Lubricant - adding wax reduces viscosity of molten polymer = less sticky = eaiser to form intricate shapes
Thermal antioxidants - prevents oxidisation or discolouring due to excess heat during process
Plasticisers - makes it less hard and brittle at normal temps eg ldpe food wrap
Also allows polmer to be easily formed at higher temps
Polymer enhancements 4 help after Pigments Antistatics Flame retardants Fillers
Pigments - tiny particles mixed in give colour
Antistatics - reduce likelyness of polymer building up static charge
Flame retardants - reduce likelyhood of combustion, spread of fire and electrical fire. Used in components, such as plug sockets
Fillers - sawdust wood flour provide bulk to product, so less polymer is required. CaCO3 can increase thermal conductivity, so heat up and cool down more so shorter mould cycle times
Polymer enhancements 4 that help degredation (or against it) Biodegradable plasticisers Bio batch additives Anti oxidants UV light stabilisers
Biodegradable plasticisers - makes it softer, easier to break down, faster to degrade
Bio batch additives - Oxy/photo/hydro degrade additives reduce degredation time from 100s y to months or years
Anti oxidants - reduce environmental degredation if polymer from exposure to O2
Prevents increased brittleness, surface cracks, pigment discolouration. Used it polymer garden furniture
UV light stabilisers - prevents polymer chain from broken down by sunlight. UV causes brittleness and colour loss. Used it outdoor garden furniture, sports stadium seats, astroturf
Wood enhancements
Resins and lamination (chipboard)
Resin with fire retardant
Lamination
Resins and lamination - used in engineered wood to enhance properties of usable parts of trees. Eg chipboard made of compressing wood chips with UF. It’s stable, not very affected by temp & humidity. No grain issues, uniform strength
Resin with fire retardant - resin had fire retardant cladding
Lamination - veneers enhance aesthetics
Wood enhancements
Preservatives
Fire retardant preservatives
Pigments
Preservatives - protect from fungal & infect attack. Eg Cu based preservatives
Fire retardant preservatives - treats wood for roof joists, cladding etc. Can also make it harder (eg for flooring situations)
Pigments - different colour enhances aesthetic
Wood enhancements
Modified natural polysaccharide
SCL and LVL
Modified natural polysaccharide - wood impregnated to cure within wood cell structure. Increases hardness, toughness, stability
Structural composite lumber & laminated veneer lumber - made by layering strands (SCL) or veneers (LVL) with UF resins, pressing, curing to produce stable wood billet.
Less prone to defects such as warping, splitting, shrinking.
Used for beams, joists
Metal enhancements
Work hardening: Def What happens to structure What properties it increases and decreases How to remove effects of work hardening
Annealing
It is when the metal is cold worked eg bending, rolling, hammering
Crystals in metal are distorted and changed and cannot move freely so u get:
Improved tensile strength and hardness
Less ductility, more cracking or damage in worked area
Effects removed by annealing
Annealing makes work hardener metal easier to work with by making it LESS BRITTLE, MORE DUCTILE obvs
Metals heated then cooled very slowly (allows crystals to go back into place)
Metals enhancements
Case hardening
What is it used for What does it produce 2 stage process Carburising and quenching What does each stage do and how
Used for hardening surface of steel with <0.4% C
Produces a very hard outer casing, but inner inner core has same ‘softer’ properties
Stage 1 - carburising
Changes chemical composition of surface of low carbon steel so it can absorb more C
(Steel placed in ceramic box, packed with C, heated to 1000. C diffuses into material, builds up surface C content)
Stage 2 - Quenching
Hot metal quenched in water to fast cool it + seal the surface case while keeping core the same
Metal enhancements
Hardening
Tempering
Hardening
Medium&high C steel heated, held at this temp for certain time, then quenched in water(oil or salt bath)
This increases hardness BUT ALSO brittleness
Tempering
This reduces excess hardness & brittleness.
Increases toughness & ductility
Metal heated to below critical point for given time, then slowly air cooled
(The exact temp determines amount of hardness removed)
