DT Unit 3 Flashcards
what is paper?
papers and boards are made from natural fibers like cellulose, usually sourced from wood.
what is the first stage in the production of paper and board?
Making the pulp:
- the natural cellulose fibers are mixed with water.
- This mixture is cooked which produce a fibrous liquid known as pulp
- pulp is fed onto a mesh conveyor which allows excess water to be drained
-this pulp makes it way through a series rollers which help to press and form/dry the pulpit a continuous sheet which is cut into sizes.
the final finish of paper or board depends upon:
- the type of fibre used to make the pulp
-any added chemicals in the manufacturing process - any added layers, different coatings or laminates
how is paper measured?
In grams per square meter (GSM)
what is bleed proof paper?
It is smooth and has a special coating to reduce absorbency
what is cartridge paper?
A thick quality paper with a slight texture
what is corrugated cardboard?
- It is made up of one or two outer flat layers and a corrugated layer.
- It is lightweight, but strong
- commonly used for delivery containers and packaging
what is foil lined board?
- It is made from a stiff card lined with aluminium foil on one side.
- it is used in cartons/boxes to make it food safe
- the card also has a waxy coating to make it resistant to oils and liquids
what is duplex board?
- it is made up of two boards
- the exterior has a wax coating to prevent moisture and looks glossy
what is foam board?
foam board consist of a sheet of polystyrene foam sandwiched between outer layers of paper
what is ink jet card?
designed for use with an inkjet printer, the inks sits on the surface of the paper.
this is due to the smooth surface, ensures even ink coverage and absorbency.
what are the properties of wood?
- aesthetically pleasing
- a good insulator
- durable and tough
what is felling?
a tree is “ felled “ when it is cut down
what are softwoods?
- softwoods come from coniferous trees.
- most trees have needles and are evergreen and keep their needles all year round.
- they grow faster than hardwood trees making it cheaper and more readily available
- the grain is wider making it more absorbent
what are hardwoods?
- hardwood is sourced from deciduous trees
- deciduous trees drop their leaves in the autumn and new leaves grow in the spring.
- hardwoods grow slower therefore more expensive
- liked due to its range in different colors and grains
- it has a closer grain making it more dense and hardwearing
list three hardwoods and their physical properties:
- oak is tough, hard and durable with a variable grain.
- beech is tough, very durable with a fine finish
- ash is very tough, also flexible and shock resistant
why is there such need for mahogany?
due its durability, color and aesthetics.
Its used for furniture, musical instruments, boats and interior panelling
list three softwoods and their physical properties:
- larch is durable, tough and good water resistance
- pine is lightweight and easy to work with
- spruce has a high stiffness to weight ratio
what is tonewood?
some woods possess tonal properties that make them ideal for use in stringed instruments
what can manufactured boards be made out of?
sawmill scraps, recycled wood, low-grade timbers and sawdust.
These woods are then bound together with adhesives.
what are the characteristics of MDF?
- very dense board which makes it tough
- its smooth surface makes it suitable for veneers
what are the characteristics of chipboard?
- good compressive strength
-edges chip easily
what the characteristics of plywood?
-made up of alternate layers of glue wood veneers
- available in different forms
what are knots in wood?
they are nature defects
what are the two ways metals can be extracted?
-electrolysis
-displacement
how can iron ore be exracted?
by using a furnace and the process of smelting
what are ferrous metals?
they contain iron and rust
what can ductile metals do?
- will stretch without being damaged
- can be drawn or stretched out into long wires
What can malleable metals do?
- can be hammered into a shape without breaking
- can be rolled pressed into sheets
what’s the difference between hard and tough?
hard- a material’s ability to withstand abrasion
toughness- how well a metal can absorb energy and resist fracturing/ deforming
what is tensile strength?
tensile strength is the amount of tensile stress (stretching) a material can withstand before breaking
what are the properties of steel?
- a ferrous metal
- high resistance to corrosion
- hardness/toughness
- it is an alloy
non- ferrous metal properties:
they are more expensive than ferrous metals due to these properties:
- lightweight
- good conductivity
-ductile and malleable
-resistant to corrosion
ferrous metal properties:
Durable
magnetic.
Very Low resistance to corrosion.
Recyclable.
Excellent conductors of electricity
what is an alloy?
metals are rarely used in their pure form.
alloys are made by combining two or more elements. This helps improve the working properties and appearance.
what are polymers?
they are synthetic materials
what are the two plastic categories?
thermoforming and thermosetting
what is thermoforming? (thermoplastics)
- when heated plastic becomes soft and flexible
-thermoplastics can be remolded without affecting the materials physical properties
what is thermosetting? (thermosets)
- the plastic cannot be reformed once set in shape
- thermosets have strong chemical bonds between the molecules, which do not separate on heating
thermoplastic pros and cons (thermoforming) :
- can be repeatedly heated and moulded
- not suitable in areas of heat or UV sensitivity
- a good surface finish can be achieved for superior aesthetics
- they can be recycled
- each time the plastic is reheated it will try to return to its original shape- this is plastic memory
thermosets pros and cons (thermosetting)
- hard/durable with good structural rigidity
- able to withstand higher temperatures
- waterproof when solid, therefore ideal with adhesives
-good electrical insulator - cannot be remoulded
what are the 4 ways plastic can be formed?
. Blow moulding - forming hollow plastic items
. extrusion - creating objects with a cross-section profile
. injection moulding- injecting softened plastic into a mould
. vacuum forming - sheet of softened plastic forced onto a mould
how many types of polyethylene is there?
- polyethylene is the most common thermoplastic
- high density polyethylene: lightweight, chemical resistant, resists cracking
- low density polyethylene: flexible, tough
- polyethylene terephthalate: lightweight, chemically resistant, stable
what is PVC (polyvinyl chloride) used for?
packaging, pipes, toys, electrical tapes, waterproof jackets
what is polypropylene used for?
soild plastics, films and fibers this is due the fact that it is low density, lighweight, ductile
what are the properties of HIPs ( high impact polystyrene)
- shatterproof
- good insulator
- lightweight
- flexible
-easily mouldable - used in fast food containers
what are the properties of acrylic polymethyl-methacrylate
- versatile
- hard - wearing
- comes in a variety of thickness and colors
- tough plastic, becomes brittle when thin
what is epoxy resin?
Epoxy resin (ER) - used as a glue, and racing car body parts mixed with carbon fibre. High strength, good chemical resistance and can be reinforced - but expensive. Good electrical insulator, hard, brittle unless reinforced, resists chemicals well
what is polyester resin?
Polyester resin (PR) A resin and a hardener, sets clear and smooth. Strong, heat resistant and good insulator, used as waterproofing and for encapsulating items
name three common textiles:
wool, cotton and linen
name the 5 textile categories:
- natural fibers
- synthetic fibres
- blended and mixed fibres
- woven and non- woven fabrics
- knitted textiles
where does cotton come from?
the fruit of a cotton plant is a capsule called a boll.
where is silk sourced from?
silk is a natural, raw fibre sourced from th cocoon of a silkworm
what are synthetic fibers?
synthetic fabrics are made from different types of polymer, derived from petrochemicals
the two types of woven textiles are:
-plain weave ( easier to produce and stronger)
-twill weave
what are non - woven textiles?
a sheet or web of fibres are bonded thermally, chemically or mechanically.
what are the two types of knitting?
weft knitting - the interlocking loops are formed horizontally, which enable it to stretch, but may lose shape
warp knitting: the loops interlock vertically , so the knit keeps it shape and is less likely to unravel or ladder
what are the properties of woven textiles?
- hard wearing
- will fray when cut
- breathable
- available in a variety of weights
- simple and most common
what are the properties of knitted textiles?
- stretchy and absorbent
- unravels easily
- thermal properties
- prone to shrinking
what are the properties of non- woven or bonded textiles?
. non -elastic
. doesn’t fray
. easy to shape and mould
. lacks strength
