plastics processing and safety issues. foam processing
TRANSCRIPT
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Plastics Processingand Safety Issues
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Foam Processing
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Nerf balls, invented by Reynolds Guyer and developed by Parker Brothers, are made from synthetic foam. Polyurethane material has CO₂ released into it during processing, creating the air pockets within the ball that make it lightweight, soft and pliable.
Foam Processing
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To create the spongy foam material, NERF begins with a reaction between polyester and a diisocyanate.
Foam Processing
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The air pockets in the foam come from the release of carbon dioxide during another reaction.
Foam Processing
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Silicone Molds & Plastic Resins
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Mold Casting
• Open mold
• Closed Mold
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Mold Casting
• Low pressure– You can use flexible molds– It is easy to get undercuts and intricate details
that are more difficult in some of the other process
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http://www.b9robotresource.com/molding1.htm
Silicone Molds & Plastic Resins
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1. The process involves heating a plastic sheet made of a thermoplastic until soft.
2. The softened sheet is draped over a mold.
3. A vacuum sucks the sheet into/onto the mold.
4. The newly shaped sheet is taken off the mold.
Vacuum Thermoforming
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Vacuum Thermoforming
Sheet of plastic Heated (soft) Molded using a shaped die
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Vacuum Thermoforming
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Advantages:• Vacuum forming uses low pressures so only
relatively low cost equipment/components are required.
• Low pressures mean that moulds can be made of inexpensive materials and in a short time..
Vacuum Thermoforming
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Disadvantages:• More complicated machines and moulds are
needed for automatic or continuous production of ‘high volume’ items, eg. disposable cups and sandwich packs.
• The vacuum forming process starts with a flat plastic sheet and there may be a need for a second process to trim the moulded end product. This means more expense to obtain additional equipment.
Vacuum Thermoforming
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These processes use composite materials – plastics made up of polymers and added material such as fiber glass or graphite fiber
Lay up processes
Graphite Fiber
Fiber Glass
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Uses of Composites
Graphite Snowboard
Composite Bicycle
Laminated Fiberglass Bow
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Dodge Viper
Front grill of an Automobile Different parts of an airplane
Uses of Composites
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Hand Lay-up
Resins are impregnated by hand into fibres which are in the form of woven, knitted, stitched or bonded fabrics. Laminates are left to cure under standard atmospheric conditions.
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Laminated Composites
Laminated composites can be thought of as sheets of continuous fiber composites laminated such that each layer has the fiber oriented in a given direction.
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Wet lay up
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Spray lay up
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Other Types of Processes
• Injection molding• Blow molding
– Injection blow molding
• Extrusion• Rotational molding• And many others!
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Injection Molding - Probably the most common, most important, most economical process
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Injection Molding
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Blow Molding
• Air pressure is used to inflate soft plastic into a mold
cavity
• Material limited to: thermoplastics
• Accomplished in two steps:
1. Fabrication of a starting tube, called a: parison
2. Inflation of the tube to desired final shape
• Two methods:
1. Extrusion blow molding
2. Injection blow molding
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Injection Blow Molding
• Preform is injection molded• Preform is placed in the blow
molding machine• Preform is heated• Preform is pressurized• Part is removed
PET Preform
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Injection Blow Molding
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Preforms Placed in Mold
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Formed Bottles
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Safety Issues
• Mechanical and pressure dangers• Thermal dangers• Eye protection (plastics are brittle)• Proper tools• Workable safety rules• Compliance with legal rules and guidelines• Gloves• Loose clothing• Emergency procedures• Proper training• Cleanliness
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Safety First
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Preventable Accidents
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Preventable Accidents
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Preventable Accidents