Finishing and Coatings
- Created by: lala2127
- Created on: 09-06-19 13:08
Types of Finishing
SELF FINISHED:
a material that has an acceptible finish after processing
SELF COLOURED:
a material that has an acceptible colour after processing
APPLIED FINISH:
a substance applied to the material after processing
Paper and Board Finishing
Provides protection for the material and allows material enhancement which is important to attract customers.
Examples:
- Laminating
- Embossing
- Debossing
- Foil Blocking
- Varnishing
Laminating
Two main methods:
lamination via encapsulation and lamination via a surface coating.
LAMINATION VIA ENCAPSULATION:
Desk top laminator - sheet of paper encapsulated by polymer pouch or film roll.
Paper fed through laminator and heat sealed leaving a polymer sheet cover on both sides.
Laminating Polymer = PET & EVA (ethylene-vinyl acetate)
LAMINATION VIA A SURFACE COATING:
- Liquid lamination: applied with roller or spray - e.g. hot and cold process for business cards. Protect against moisture and UV light.
- Film lamination: usually made of PP with adhiesive. Laminate fed from roller and pressure is applied as paper feeds through.
Embossing
a raised design on the surface of the paper or card.
Examples:
- greeting cards, invitations, packaging
PROCESS:
Uses 2 dies - male and female - made from stainless steel/brass - cold or heated.
1. Substrate places between 2 dies (moulds) and held under pressure.
2. Embossed area is formed.
3. Can have ink/foil applied to raised area or natural (blind emboss).
Debossing
imprinted depression which sits below the surface of the paper or card.
Examples:
- greeting cards, invitations, packaging
PROCESS:
1. paper or card goes between 2 dies.
2. depression is made - indent the card
(same process as embossing)
Foil Blocking
application of heat and pressure to a metalic paper (foil) to create areas of depth and texture.
Purpose: add aesthetic impact.
Different types of foil:
- metallic, gloss, matt, clear, holographic
Examples:
- business cards, company logos
PROCESS:
1. Design stamped onto material through the foil (special machine - heated die)
2. Heat allows foil to stick to paper or board
requires accuracy and consistancy
Varnishing
Varnish: clear, non pigmented ink used on pre coated paper and boards to enhance the colour and provide protection.
2 types of varnishing:
- UV Varnishing and Spot Varnishing
UV VARNISHING:
Smooth finish - ink must be dry before applied - spesific machine - high quality finish (high, gloss, matt) - abrasian & chemical resistant - sheet passed through UV light to cure.
SPOT VARNISHING:
Applied to spesific areas - plate or set of plates press onto surface - varnish is applied to that spot - can use varnish / UV varnish.
Polymer Finishing
Polymers = self finishing materials - need no additional finishing process
Ready to use.
Pigments can be added during manufacture to enhance colour, and surface textures are produced from the mould.
Different processes include:
- Adding colour in the moulding process
- Acrylic spray paint
- Overmouldings
Adding Colour in the Moulding Process
Pigments: tiny particles, added to the polymer to create a particular colour.
- added during manufacture process.
- manufacture would buy pre-pigmented granuels.
SMART PIGMENTS:
- e.g. thermochromic or phosphorent pigments (glow in the dark)
added in same way - produce ready-finished products.
Metal Finishing
Most metals = oxide layer - provide barrier against environmentle effects
Example - COPPER:
- Bright red colour (originally)
- Overtime - oxide layer forms to protect from corrosion and environmentle attack
Finishes are applied because... enhance apperance and provide barrier against corrosion
Different metal finishing processes:
- Cellulose and Acrylic Paints
- Electroplating
Cellulose and Acrylic Paints
Paint - provides colour & textured finish to metals & barrier against corrosion.
usually used on low cost metals (e.g. steel)
1. Surface of metal must be clean and degreased before application - can 'grip' onto metal
Application:
- brush or spray
REQUIRE PRIMER LAYER BEFORE PAINT
Electroplating
using a metal to coat a base metal.
Provides... protective layer, aesthetics, barrier from corrosion.
Commonly used metals:
- silver, gold, zinc, copper, tin
Process:
1. product and coat metal placed in container with electrolyte solution.
2. direct current is applied.
3. product attracts coat metal and product is electroplated.
Dip Coating
Polymer dip coating.
Examples of products:
- wire coat hanger, dish drainers, dishwasher racks, outdoor play frames
Process:
1. metal heated to approx. 230 degrees celsius.
2. hot product is dipped into tank of fine polymer powder.
3. air blows through it (fluidisation bath).
4. fluidisation = even coating.
5. retained heat - polmer melts over metal & is air cooled.
Metal Dip Coating
metals coated with other metals.
Before... must be clean and degreased.
TIN PLATING: e.g. food cans
- Sheets of steel through molten tin tank (320 dc).
- Non corrosive coating.
ZINC PLATING: e.g. animal pen
- aka. galvanising
- Dipping steel into molten zinc (460 dc).
- Industrial and agricultural applications.
- Protective layer.
Wood Finishing
Purpose of wood finishing:
- prevent moisture absorbtion
- protect against decay / insect attack
- enhance apperance
Natural wood can degrade by...
1. Alternating wet and dry
2. Insects
Preperation:
- make it smooth - planning or sanding (direction of grain)
- cloth - wipe away excess dust
Acrylic Varnish
Types of surface finish: gloss, satin or matt
Available in: clear or colour
How to apply:
- brush, roller or spray
- several thin coats - rub down between coats
Properties:
- hard, tough, heatproof, waterproof
- clear finish - grain can be seen
Water - Based Paints
Available in... gloss, satin, matt and metallic
How to apply:
- brush, roller or spray
Before Application:
1. treat wood knots
2. prime surface & add undercoat
Properties:
- protection, colour, indoor / outdoor, softwoods, aesthetic, resistant to moisture
Pressure Treating
Process:
1. wood is placed in a pressure vessel - solution (copper sulfate + salts)
2. vaccum and pressure controlled to force preservative into fibres of wood
2. wood is steam dried
Properties:
- protect wood up to 50 years
- protect from rot, insect and fungal attack
Examples of products... decking, harbour, bridge
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