Lecture 3 Flashcards
Plastic Characteristics
Most versatile and useful material. Can take the place of various materials like wood, glass, china, cloth, rubber, jewels, varnish
Polymers Characteristics
Derived from the imagination of the chemist, composed of atoms carbon, hydrogen, oxygen, chlorine, and sometimes nitrogen and fluorine. Synthesized from oil.
What are some of Nature’s Polymers / Oldest worldly materials
Woods, wools, leather
What is the first plastic
Cellulose nitrate (Celluloid)
Three original Plastics
Cellulose Nitrate (Celluloid)
Casein Plastics
Phenolic Plastic Bakelite
How are plastics Named
By their most basic chemical compounds
Who is involved in the plastics industry
Chemical Companies
Plastic Processors
Fabricators
The role of chemical companies in the plastics industry
Obtains ethers, alcohols, esters, acids, and raw materials for resins
Who are the Processors in the Plastics Industry and what do they do
Moulders, Extruders, Coaters, and convert the plastic compounds into useful forms
What is the Fabricator’s role in the Plastics Industry
Convert the various resins and forms into finished products
What is the composition of plastics
Synthetic organic compounds that are man made and organic because they have carbon
Other elements/materials that can be used for plastics
Hydrogen, oxygen, chlorine, and sulfur. Coal, Petroleum, Cellulose (Cotton Fibres)
Two main classifications of plastics
Thermosets and Thermoplastics
Thermoset Plastics
Soften with heat but stay soft for a short time. They set when heat continues and can’t be soft again
Thermoplastics
Plastics set with heat but remain soft if they are heated. Only sets when cooled and can be resoftened by reheating
Elastomers
A thermoset that retains their shape even when stretched 4 - 5x their original length
What are examples of Thermoplastics
Polymers, Polypropylene, Acrylonitrile-Butadiene-Styrene
Polystryene
Brittle in its simplest form but can be made in a high impact variant. Has a weak tensile strength and can crack easily. Easy to mould and can be coloured and made clear.
Uses of Polystyrene
Food containers, packaging, ceiling tiles, refrigerator trays
Polypropylene
Exceptional strength and resilience, resistant to water
Uses of Polypropylene
Ropes, automobile ducts, garden furniture, artificial turf, thermal underwear
Acrylonitrile-Butadiene-Styrene
Tough, resilient, and easily moulded. Opaque but can be transparent and pigmented. Good chemical, temperature and high impact resistance
Typical uses for Acrylonitrile-Butadiene-Styrene
Computer and TV cases, telephones, food mixers, vacuum cleaners, bath trays, plumbing pipes, RV Parts, shower stalls, sports equipment
What is casting
A limited production process most often used for part evaluation or pre-production parts.
What materials can moulds be made from?
Moulds can be made from rigid or flexible materials.
What is the usual composition of the mixture used in casting?
A two-part mixture of a monomer and a catalyst, plus additives such as pigments, fillers, and reinforcements.
What is a unique property of thermoset materials in casting?
Thermoset materials usually generate their own heat in reaction to the catalyst.
How are thermoplastics prepared for casting?
Thermoplastics are usually heated before being poured into the mould.
What are the most commonly cast thermoset materials?
Epoxy, phenolic, polyester, and polyurethane.
Which thermoplastics are most commonly used in casting?
Nylon and acrylic
What is foam moulding used for in the furniture industry?
To produce cushions and other forms using flexible polyurethane resins
What is the purpose of rigid foam materials in the construction industry?
To produce insulating blocks and foam core interior and exterior building products
What determines the density of foam in foam moulding?
The pressure created by the volume of the mixture in the mould and the amount of gas injected into the mould
What is contact moulding
Hand lay-up or contact, a labour intensive process typically used in low to moderate production of small to large parts
Typical materials for contact moulding
Plastic, wood, and plaster
What is contact moulding used for
Making boat hulls, tub and shower units and other large housings
Types of Resin Moulding
Reaction Injection Moulding
Compression Moulding
Pultrusion
Rotational Moulding
Injection Moulding
Co-Injection
What is Reaction Injection Moulding
Inexpensive, where resin and catalyst mixture is combined and chemically reacts in the mould cavity
What is compression moulding
Used with thermosetting resins and rubbers where a measured amount or a preform of a partially polymerized is placed by hand into a preheated mould
What is Pultrusion
The process produces shapes that are similar to extruded shapes in that they have a constant profile and indefinite length
What is Rotational Moulding
Labour intensive, used to make large parts, where material is loaded into a two part metal mould and heated in a large oven while being rotated about the two axes
What is Injection Moulding
Used with thermoset and thermoplastic resins where pellets are fed through a hopper into a heated barrel where they are mixed with additives and melted
What is Co-Injection
Machines use reciprocating screws to create the force required to inject the liquefied resins into a mould cavity at the pressures of 1 tonne psi
What is Polyvinylchloride
PVC. One of the cheaptest and versatile polymers. Rigid but not very tough. Made to resemble colour and texture but less transparent than polycarbonate
Uses of PVC
Lightweight panels for car interiors, pipes, fittings, profiles, road signs, garden hoses, medical tubes, dolls
What is Polyamid / Nylon
Strong, durable, low coefficient for friction, has a wide scope of temperatures for injection moulding. Transparent or tinted with pigment
Uses of Nylon
Light duty gears, ropes, bushings, car fenders, ketchup bottles, book bindings, garment design
What is Acrylic
Hard, stiff, clear or coloured, scratches easier than glass but can be removed
Uses for acrylic
Eyeglass lenses, aircraft windows, baths, lighting, tail lights, advertising signs
What is Polycarbonte
Optical transparency, tough and rigid at high temperatures
Uses of Polycarbonate
Compact disks, hair dryer housings, toasters, printers, power tool housings, fridge linines, car parts, helment visors, riot shields
What is Polyurethane
Easily foamed, soft and stretchy, slow to burn
Uses of Polyurethane
Garment material, fridge insulation, and car crash protection
What is silicone
Chemically stable elastomers, good electrical properties at low strength, similar to rubber
Uses of silicones
Wire and cable insulation, mould release agents, lens cleaning tissue coatings, adhesives, insulation, swimming google seals
What is Polyester
Flame retardant thermoplastic, able to withstand high pressures and mimic elastomers
Uses of Polyesters
Carbonated drink containers, oven proof cookware, windsurfing sails, brushes, boats and car parts, decorative film
What is Polyethylene
Strong mechanical stiffness and strength, cheap and easy to mould and fabricate
Uses of Polyethylene
Oil containers, milk bottles, toys, beer crates, food packaging, squeeze tubes, film and packaging
