plastic finishes final

Plastic Finishing ProcessesAndrew Briggs, Lance Baresic, Tia Johnson, Yesenia Alvarado

Presentation Overview

• Contents

• Surface Treatment ProcessesThree major processesEquipment 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

ContentsThe 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– In-Mold Decoration

• Printing • Laser Marking

• Vapor polishing

• Decals

• Economics (comparison of processes)

• Case Study – Lectro-Treating

• Conclusion

Cleaning

• Air Bath

• Suitable Solvents (i.e. Alcohols, Aliphatics, Aromatics, Ketones, Chlorinated Hydrocarbons)

• Automated Cleaning Line

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

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.

Flame Treatment

Hot Knife

Flame Torch

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).

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.

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.

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)

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

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.

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.

Electrolytic PlatingElectrolytic 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.

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

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

Metallizing

Benefits

• Low weight

• Corrosion resistance

• Greater styling possibilities

• Ease of assembly

• Controllable electrical conductivity

• Low costs.

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

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.

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

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.

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)

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.

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.

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.

Economics

Process Low Cost High cost

Reason

Cleaning x

Flame De-burring x x Low cost: manual operationHigh cost: automatic

Hot Knife de-burring x

Corona Treatment x

Plasma Treatment x

Painting and coating x

Plating x

Hot stamping x

Hot transfer x Pre-printed film available. More expensive than hot stamping

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.

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.

Case Study - Lectro-Treating

Disadvantages• Can’t be used to clean the surface.• Process is proprietary.

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.

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 plastic’s strength, wettability and resistance to damaging environmental factors.

Questions?