Plastic Finishing Processes

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Plastic Finishing Processes

• Andrew Briggs, Lance Baresic, Tia Johnson,
  Yesenia Alvarado

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Presentation Overview

• Contents
• Surface Treatment Processes
• Three major processes
• Equipment used is shown
• Paints Coats - Advantages/Disadvantages
• Metallization
• Heat Treatments
• Other surface decoration processes
• Economics (Pros/Cons for each process)
• New Technology - Case Study
• Conclusion

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Contents

• The most commonly used methods for finishing and
  enhancing plastics are
• Cleaning
• Surface Treatments
• Flame Treatment
• De-Burring
• De-Flashing
• Wettability
• Corona Treatment
• Wettability
• Plasma Treatment
• Wettability
• Painting and Coating
• Metallization
• Plating
• Vacuum metallization
• Flame or Arc Spraying
• Heat Treatments
• Hot Stamping
• Hot transfer

• Printing
• Laser Marking
• Vapor polishing
• Decals
• Economics (comparison of processes)
• Case Study Lectro-Treating
• Conclusion

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Cleaning

• Air Bath
• Suitable Solvents (i.e. Alcohols, Aliphatics,
  Aromatics, Ketones, Chlorinated Hydrocarbons)
• Automated Cleaning Line

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Surface Treatments

• Necessary for proper adhesion of glues, inks,
  paints.
• Used to improve appearance, corrosion resistance,
  wear resistance and other surface flaws.
• Plastics that require treatment include
• - Polyolefins
• - Thermosets
• - Engineered Plastics
• Results in increased surface tension, and
  wettability of plastic parts.
• Treatments Include
• Flame Treatment
• Corona Treatment
• Plasma Treatment

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Flame Treatment

• Flame Treatment is a method of chemically
  changing the surface molecular structure of a
  substance in a controlled manner to increase
  surface energy and wettabililty.
• Applications wheel covers, air spoilers, door
  handles, dashboards, bumper fascias.
• Advantages controlled process, repeatable
  results, low capital cost, environmental
  friendly.
• Example
• Flame De-Burring Also known as Torch De-burring
  used for trimming flash, sprues, and gates from
  large castings.
• Hot Knife De-flashing the use of a thermally or
  warm knife to cut off flash from plastic parts.
• Wettability the level of energy in the surface
  of material, the more wet the surface is the
  higher the amount of electric charge on the
  surface, resulting in higher attraction to
  paint.

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Flame Treatment
Hot Knife
Flame Torch
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Corona Treatment

• A surface treatment process that improves the
  bonding characteristics
• of most materials such as paper, films, foils,
  and polymers by raising
• Surface energy (dyne level).

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Plasma Treatment

• Uses hot plasma gases to treat surface.
• Plasma- a state of matter in which gas molecules
  come apart and become intensely reactive.
• Surface preparation used prior to printing,
  bonding and coating plastic parts.
• Replaces wet chemical and abrasive processes
  currently used.

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Painting Coating

• Used to make a product more attractive or protect
  it from the elements.
• For example the paint finish on an automobile,
  makes the vehicle more attractive and provides
  protection from corrosion.
• Various techniques to apply paint/ coating dip
  product in paint, spray product with paint, and
  powder coating.

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Painting Coating

• Advantages
• Aesthetics to hide irregularities in the
  substrate free choice of color-gloss-structure
  color matching with adjacent parts
• Improved chemical, abrasion or UV-resistance
• Electrical conductivity
• Electromagnetic shielding
• Styling versatility
• Manufacturing convenience (when compared to
  non-painting/coating processes for the same tasks)

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Painting Coating

• Disadvantages
• Paint can fracture before plastic does.
• Paint layer can result in a 40-fold reduction of
  the fracture energy especially when too rigid a
  paint is used
• Solvents in paint

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Metallization - Plating

• Plating describes surface-covering where a metal
  is deposited on a conductive surface.
• Plating processes can be divided into two
  categories Electroless - A plating process
  without a galvanic electric current.
• Electrolytic - A plating process with a galvanic
  electric current.

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Electroless Plating

• Electroless Plating is the deposition of a
  metallic coating on electrically nonconductive
  plastics.
• Process
• The surface of the part to be plated is first
  etched with a strong oxidizing solution that
  partially erodes the plastic surface, creating
  microscopic holes.
• The enlarged surface area created makes the
  surface hydrophilic, enhancing the bonding of the
  plastic to the deposited metal.
• After etching, the part is immersed in a solution
  and a metallic coating is formed in a chemical
  reaction between the reducing agent present in
  the solution and metal ions.

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Electrolytic Plating

• Electrolytic plating is the deposition of a metal
  on a conductor using an electric current.
• Process
• A plastic surface must first be made conductive
  in order to be electrolytically plated. This can
  be done through electroless plating, conductive
  paints, or by the use of conductive additives
  such as carbon.
• The part to be electrolytically plated is
  immersed in a solution of metal salts connected
  to a cathodic direct current source, and an
  anodic conductor is immersed in the bath to
  complete the electrical circuit.
• Electric current flows from the cathode to the
  anode, and the electron flow reduces the
  dissolved metal ions to pure metal on the
  cathodic surface. The anode is usually made from
  the same metal, and dissolves during the
  electroplating process, replenishing the plating
  bath.

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Metallization - Vacuum Metallization

• Vacuum Metallizing is the
• process in which a metal is applied to a
  nonporous substrate such as plastic, metal or
  glass.
• Products
• Christmas ornaments
• Road reflectors
• Head lamps
• Tail Lights
• Bicycle Reflectors
• Thermal Blankets/Suits

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Metallization - Flame or Arc Spraying

• In flame spraying, a metal powder or a wire is
  heated and propelled onto the plastic substrate
  by a stream of hot gases.
• A fuel gas, usually acetylene or propane, is fed
  through a central nozzle and supplies the
  necessary energy to melt the metal.
• Arc spraying is comparable to flame spraying, but
  in arc spraying a DC electric arc is used

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Metallizing

• Benefits
• Low weight
• Corrosion resistance
• Greater styling possibilities
• Ease of assembly
• Controllable electrical conductivity
• Low costs.

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Heat Treatments

• Heat treatments are used to heat the surface of a
  plastic and enable plastics to undergo decorative
  processes that make such plastics more appealing.
• Processes include
• Hot Stamping
• Hot Transfer
• In-Mold Decoration

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Heat Treatments Hot Stamping

• Is a fast and easy process to provide parts with
  a decorative pattern or lettering.
• The image is transferred from a carrier foil to
  the part with the help of a heated stamping press
  as shown below.
• It is a dry process and the parts can be handled
  immediately after stamping.

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Heat Treatments Hot Transfer

• Hot transfers can be used to provide parts with a
  decorative pattern or lettering.
• They consist of a pre-printed transfer film, on
  which the design has been applied. A hotplate is
  used to transfer the color coating from the film
  onto the part under pressure.
• Pre-printing the film makes the hot transfer
  process relatively expensive compared to hot
  stamping

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Heat Treatments In-Mold Decoration

• In mold decoration is a decorating process that
  can be integrated in the injection molded
  process.
• Advantages over conventional coating
  procedures- lower costs, no separate painting
  line,- reduced or eliminated emissions of
  volatiles,- no heat-curing restrictions, and
  multi-color patterns possible.
• Disadvantage makes the injection molding process
  more complicated.

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Printing

• Printing- plastics can be printed to provide them
  with a decorative pattern, logos or lettering.
• TYPES OF MARKS Date / Product Coding Dot / Spot
  marking Logos
• PRODUCTS MARKED Plastic, metal, glass Rubber
  products Paper Cardboard Flexible / Rigid
  containers Films
• SURFACES MARKED Porous Non-porous, Stationary
  Moving (limited), Flat Curved / Round (limited)

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Laser Marking

• Laser Marking- The traditional method of writing
  on plastics is printing with ink. Direct ink
  printing puts an image on the surface whereas
  laser marking can provide an indelible, high
  contrast mark under the surface.

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Vapor Polishing

• Vapor polishing- The process is performed with a
  chemical vapor, which attacks the surface of the
  plastic and smoothes it. When done properly,
  vapor polishing can provide optical quality
  finishes.
• Advantages provides smooth surfaces if done
  well.
• Disadvantages harmful vapors/chemicals
  (Methylene chloride) are used and special
  equipment is needed. Costly.

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Decals

• Decals- They are made of a pre-printed and
  pre-cut carrier, like a polymer film or paper,
  with a pressure sensitive adhesive backing and a
  release sheet.

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Economics
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Case Study - Lectro-Treating

• Proprietary process by Lectro-Engineering.
• Treats surfaces the same way, flame, plasma, and
  corona do.
• Uses cold plasma moving parallel to the material.
• Process can be continuous or batch oriented.

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Case Study - Lectro-Treating

• Advantages
• Treats the entire surface, not just the surface
  that comes into contact with the treatment.
• Does not require heat.
• Surface cannot be over-treated.
• Does not affect the properties of the plastic
  beneath the surface.
• Does not cause warpage, burning, or oxidation.

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Case Study - Lectro-Treating

• Disadvantages
• Cant be used to clean the surface.
• Process is proprietary.

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Future Treatment Process

• From Lectro-Engineering
• Surface treatment can now be done to resin power.
• Now treated plastic resins can be molded and
  instantly be ready for painting, etc.

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Conclusion

• To Review
• Surface finishing processes for plastics which
  are important to enable the ease of paint,
  adhesives and other desired chemicals to attract.
  
• These processes enable a high quality
  part/product because it increases the plastics
  strength, wettability and resistance to damaging
  environmental factors.

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• Questions?