tailieunhanh - Plastic part manufacture, injection molding

In the last 30 years, plastics have become the most dominant engineering material for most products. We take a brief look at the most common types of plastics, and how they are processed. All plastics are polymers, these polymers are further divided into two basic types: thermoplastics and thermosets. | 1 Lecture 7. Plastic Part Manufacture Injection Molding In the last 30 years plastics have become the most dominant engineering material for most products. We take a brief look at the most common types of plastics and how they are processed. All plastics are polymers these polymers are further divided into two basic types thermoplastics and thermosets. Thermoplastics melt when heated - so they can be melted and re-formed again and again. Thermosets harden when they are heated if heated further they will break down chemically and lose their properties. Some thermosets have properties very similar to rubber and are used as synthetic rubber they are categorized as elastomers. Here are some typical plastics and their uses Thermosets General properties more durable harder tough light. Typical uses automobile parts construction materials. Examples Unsaturated Polyesters lacquers varnishes boat hulls furniture Epoxies and Resins glues coating of electrical circuits composite materials like fiberglass used in helicopter blades boats etc Elastomers General properties these are thermosets and have rubber-like properties. Typical uses medical masks gloves rubber-substitutes Examples Polyurethanes mattress cushion insulation toys Silicones surgical gloves oxygen masks in medical and other applications joint seals . Thermoplastics General properties low melting point softer flexible. Typical uses bottles food wrappers toys . Examples Polyethylene packaging electrical insulation milk and water bottles packaging film Polypropylene carpet fibers automotive bumpers microwave containers prosthetic body parts for disabled people Polyvinyl chloride PVC sheathing for electrical cables floor and wall coverings siding credit cards automobile instrument panels 2 Polystyrene disposable spoons forks etc. also used to make Styrofoam soft packaging material Acrylics PMMA polymethyl methacrylate paints fake fur plexiglass Polyamide nylon textiles and fabrics gears bushing and washers bearings