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Emerging material to the desired thickness using a 3

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Unformatted text preview: erature Cutting to required width and length and subsequent stacking on pallets Extrusion Extrusion Extruder Equipment Exit zone- die die imparts shape on the material, e.g., rod, tube, sheet, channel exit material is called extrudate extrudate swells at end of die due to normal forces from the polymer flow, called die swell Cooling zone water bath or air cooled to lower the temperature below Tg Auxiliary equipment puller rollers for proper thickness Wind-up or cut off Single Single screw extruder Extruder Extruder Types Single screw Most common A screw rotates in a cylinder and creates a pumping action. Twin Screw Twin screws have more positive pumping action than single screws and can be used for higher output. Co-Rotating Twin Screw: popular for compounding Counter- rotating Twin Screw Extruders Extrusion • Principle – Continuously shaping a fluid polymer through an orifice of a suitable tool (die), and subsequently solidifying into a product. • Equipment – Single screw extruder consists of • Screw, barrel, feed hopper, and die – Common extruders are rated by barrel bore diameter (0.75” to 6”) – Plastics extruders can be 24” diameter and 48 ft in length – Electric heaters for barrels and Air (or water bath) coolers for extrudate – Screw is matched to material produced – Simple screw has flights and decreasing gaps along channel – Screw Aspect (L/D) ratio = screw length to screw diameter (range 20-30) – Venting zone for gases that evolve during processing – Twin screw- used for shear sensitive materials (e.g., PVC) Plastic Plastic Extrusion Sheet Extrusion Profile Extrusion Pipe extrusion Co-extrusion Blown Film Extrusion Cast Film Extrusion Foam Extrusion Pultrusion Calendering 1 Drive unit 2 Barrel inlet 3 Temperatue control 4 Feed hopper and dosing unit 5 Vacuum venting 6 Barrel 7 Screws Single Single screw extruder 1 Drive unit Powerful, low-noise gearbox, with hardened and ground gear wheels in a cast housing with oil immersion lubrication. Direct drive by means of clutch, with either AC or DC technology. EXTRUDER EXTRUDER Extruder Extruder base- used to isolate extruder...
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