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design technology :smiley: (paper and board (The first stage in the…
design technology :smiley:
timber
wood
Wood has played a key role
in the history of civilization
Man has used wood over
the centuries for many
purposes, both practical
and decorative
Natural wood is categorised as either hardwood
or softwood
A useful and
versatile material, wood is:
Aesthetically pleasing
A good insulator
Durable and tough
Wood generally has a good
strength to weight ratio
Softwood comes from
coniferous trees
Most coniferous trees have needles, are evergreen, and they keep their needles all year round
Softwood trees grow faster than hardwood trees making it relatively cheap and readily available
The grain is wider making it
more absorbent
Hardwood is sourced from deciduous trees
Deciduous trees drop their leaves in the autumn and new leaves grow in spring
Hardwood is slower growing and
is therefore more expensive
Sought after for its variety of colours and grains, it has good aesthetical and physical properties
It has a closer grain, making it more dense
and hardwearing
Natural timbers can have natural defects
The most common natural defect is a knot
Softwoods such as pine, larch and cedar
can also seep resin at the knot
paper and board
The first stage in the production of paper and board is to make pulp.
Papers and boards are made from natural fibres (cellulose), usually sourced from wood.
The natural cellulose fibres are mixed with water
This mixture is cooked which produces a fibrous
liquid known as pulp
Pulp is fed onto a mesh conveyor which allows excess water to drain away
This makes its way through a series of rollers which help to press, form and dry the pulp into a continuous sheet which is either rolled or cut to size for commercial processing.
The final finish of paper or board depends upon:
the type of fibre used to make the pulp
any chemicals added during the manufacturing process
the addition of layers, different coatings or laminates
bleaching level which decreases the natural colour so it becomes whiter.
paper
Paper is characterised by weight
The weight is measured in grams per square metre (GSM)
Understanding the different types of paper available will help you select the right material for the job.
Cardboard,
A heavy duty paper available in a range of thicknesses and strengths.
Corrugated board is made up of
one or two outer flat layers and a corrugated layer.
textiles
Textiles can be manufactured to exhibit a variety of properties depending on the blend of fibres
Categories include:
Natural fibres
Synthetic fibres
Blended and mixed fibres
Woven and non-woven fabrics
Knitted textiles
The fruit of a cotton plant is a capsule called a ‘boll’
The mature seed splits open
to reveal the fibres
Once harvested, the fibres
are spun into yarn
Cotton is soft, strong
and easily washable
Silk is a natural, raw fibre sourced from the cocoon of the larvae of a silkworm
metal and alloys
The Earth’s crust contains many types of rock
Metallic minerals are found naturally in rock or ore
Ore is obtained by mining and the metals within it
are extracted
The method used for extraction depends on the
metal’s reactivity with air, water or acids
The more reactive the metal, the more expensive it is
to extract
Some naturally occurring metals are found as lumps in the rock and don’t require a chemical extraction
Ferrous metals contain iron and may rust
Iron and steel can corrode – this is known as rust
Rust is a compound called iron oxide and is formed when iron and oxygen react in the presence of moisture or water
Most ferrous metals are magnetic
Non-ferrous metals don’t contain iron
They are often more expensive than ferrous metals owing to their desirable properties which include:
Lightweight
Good conductivity
Ductile and malleable
Resistant to corrosion
The process of galvanising adds a
protective coat of zinc to iron and
steel to help prevent rusting
Conductivity is how easily an electrical current can flow through a metal