Plastics Processing and Safety Issues

Foam Processing

Nerf balls, invented by Reynolds Guyer and developed by Parker Brothers, are made from synthetic foam. Polyurethane material has CO ₂ released into it during processing, creating the air pockets within the ball that make it lightweight, soft and pliable. Foam Processing

To create the spongy foam material, NERF begins with a reaction between polyester and a diisocyanate. Foam Processing

The air pockets in the foam come from the release of carbon dioxide during another reaction. Foam Processing

Silicone Molds & Plastic Resins

Mold Casting Open mold Closed Mold

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

Silicone Molds & Plastic Resins

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

Sheet of plastic  Heated (soft)  Molded using a shaped die

Vacuum Thermoforming

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

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

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

Uses of Composites Graphite Snowboard Composite Bicycle Laminated Fiberglass Bow

Dodge Viper Front grill of an AutomobileDifferent parts of an airplane Uses of Composites

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.

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.

Wet lay up

Spray lay up

Other Types of Processes Injection molding Blow molding –Injection blow molding Extrusion Rotational molding And many others!

Injection Molding - Probably the most common, most important, most economical process

Injection Molding

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

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

Injection Blow Molding

Preforms Placed in Mold

Formed Bottles

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

Safety First

Preventable Accidents