The Use Of Finishes Flashcards
What are the purposes of getting finishes for wood?
Prevent the wood from absorbing moisture
Protect against decay
Protect insects attack
Enhance the appearance of the material
What are the main ways wood can degrade?
Alternating wetness and dryness means hat moisture is absorbed into the wood and although the surface may dry out moisture remains below the surface - this causes the wood to break down of the wood fibres and a fungus which thrives in the damp conditions with little air circulations to spread
This makes the wood wet and in a crumbly state. The fast growing fungus causes it to rot which an quickly turn the wood into a dry soft powdery state
Insects which attack where e.g. beetles in hardwood lay eggs in the cracks of the wood and latched larvae eat into the wood and create tunnels and a beetle forms eating out of the wood
What are the conditions needed before applying a finish to the wood? How should we sand the wood
Should be made smooth by either sanding or planing the wood using glass paper e.g. progressively with finer grades.
The wood should be sanded in the same direction as the wood grains to avoid scratching the wood surfaces. Finally a cloth should be applied to wipe away the remains dust and sand before the finish is applied
What is foil blocking used for?
Used for business cards by adding depth and texture the to material and an aesthetic impact with a metric and glossy finish to enhance letterheads
It uses a heated die to allow it to be stamped onto a material where a foil sheet is paced in between the material and heat allows the foil to stick to the paper
Requires accuracy and consistency if not heated for the correct amount (overboard) the foil will bubble and peel if not high enough the foil will not stick to the substrate paper
Varnish is a clear liquid, non pigmented used to enhance colours and offer protection against dirt, finger prints and water - in terms of paper and boards
A range of inks like gloss and stain are available with varnish to be used
It is only suitable to be used on pre coated papers since they will not soak up the ink and swell as a result of the bleed colour
What type of finish does uv varnish do?
A clear finish but the ink must be completely dry before being applied - usually a high mat or gloss finish and has abrasive and chemical resistance. Applied with a eat of rollers
Spot varnish is used to target specific areas rather than the whole area. A set of plates are pressed onto the surface and apply the varnish to that spot.
What does the term substrate mean?
Refers tot he material on to which the print ink is applied - e.g. paper and boards
How is a simple screen print made?
Image is crazed on a screen which is a mesh held by a frame - the frame has open areas for ink to pass through. Each colour has its own screen. This increases time taken and is a disadvantage to this setup as well the cost per ite
The screen is then placed over the substrate on the machine bed
Pigmented printing ink is then placed on the screen a squeegee is then used to force the ink to flow through the mesh onto the substrate
Once each colour cis complete the substrate is left to cure and complete the print
The use of acrylic spray paint on polymers: in terms of mass customisation e.g. cars
Additional finishes can be used on polymers even though they are self finishing to improve product function.
Mass customisation allows for customers to chose from what colours and specs they want e.g. colour coding bumpers and mirrors to match the colour of the body as well as wing mirrors
What manufacturers will do is make these products out in a base colour and use acrylic spray paint to provide the colour that the customer wants - which saves on costs and materials used since changes to demand may effect sales and some colours may not be wanted more than others so uses pigments during the production stage is not beneficial
Over moulding is done for added a second layer onto a part of the product. using TPE often they are primarily used as grip texture and to highlight different colours and functions of a product. What are the two ways that they can be made using this method? E.g to provide an are of grip to a product
Using injection moulding moulds where one mould is made for the product and one mould is made for the grip area. The toothbrush e.g. mould is used via injection moulding and then is placed in a second mould to fill in for the new areas for grip
Twin shot unction moulding: using injection moulding to produce the product all in one go. It does this by having two holes called ‘cavities’ which can be rotated 180 degrees to line up with the polymer. Once the first mould is done the second one will begin applying the grip to the product. And this can occur with other models beginning the process for the first mould as well
Note: most polymers are made form finite material and don’t degrade until after a few hundreds of years. Those that cause these contaminations are also dangerous to habitats and wildlife including sea animals as well.
However polymers can be produced from natural and organic material like vegetable oil and plants + sugar and starch - the use of bio polymers has increased over the years
Bio polymers can be split into two different categories: state them and some of their properties
Natural bio polymers: made form natural materials like cellulose and starch and polysaccharides
Synthetic bio polymers: made form renewable resources but chemically engineered to break down more quickly e.g. PLA
Polymer can extraction can occur when…
A polymer is exposed to a significant change in the properties when they are in areas of the influence to chemicals, heat and light
Bio-polymers contain tiny microorganism which allow for the material to break away much faster when exposed to its natural enemy either oxygen, water of light. These can be done to enhance properties using additives and are mostly used in LDPE HDPE PP PVC AND PET
What do these tiny organisms do?
They convert the bio-plastic into CO2 and biomass like CH4 methane - degrading from up to weeks to months
Oxy degradable polymer:
The polymer breaks down into fine powder with the exposure to oxygen and is subsequently degreased by the action of micro organism - length of time can range from a few months to a few weeks. Commonly used in LDPE plastic bags
How does a photodegradable polymer work?
The polymer bonds are weakened by uv wavelengths of light. Often sued in the agricultural industry where a ground of pants may be converted by a polymer sheet which acts as a a mulch to prevent weed growth and as it slowly decays it halts the weed growth. The sheet also helps trap water
How does a hydro-degradable polymer work?
The polymer breaks down with the exposure to water and subsequently microorganisms - they tend to degrade more quickly than oxy-polymers
This additive is often used in liquid detergents for household washing machines or dishwashers or used in single wear packaging. They dissolve in contact with water
