DTEL 1 UNIT vI PLASTIC AND PLASTIC PROCESSES

DTEL 2DTEL 2 CHAPTER 6:- SYLLABUSDTEL Introduction to plastic,propertise & types, Plastic process introduction and application Forming and shaping of plastic Extrusion,injectionmoulding,Blow moulding,wire moulding Compression moulding

DTEL 3 Processing of Plastics LECTURE 39 Introduction to plastic,propertise & types

DTEL 4 Processing of Plastics T hose methods used to convert plastics materials in the form of pellets, granules, powders, sheets, fluids, or performs into formed shapes or parts. The plastics materials may contain a variety of additives which influence the properties as well as the process ability of the plastics. After forming, the part may be subjected to a variety of ancillary operations such as welding, adhesive bonding, machining, and surface decorating (painting, metalizing). LECTURE 40 Plastic process introduction and application

DTEL 5 Thermoplastics (resins) Thermoplastics soften when heated and subsequently melt. When cooled they become hard and rigid once again. Example: Polyethylene, PVC, Nylon Uses: Bags, Mugs, Toys LECTURE 41

DTEL 6

DTEL 7 Forming and shaping plastics & composite materials LECTURE 42 Forming and shaping of plastic

DTEL 8 Injection Moulding Injection moulding is one of the most important industrial processes in the mass production of plastic goods. The cost of machining the original moulds can be very high. Therefore it is necessary to sell large numbers of the products being manufactured to recover costs. LECTURE 43 Extrusion, injection moulding

DTEL 9 Typical Materials Used Most thermoplastics can be processed by Injection Moulding. The table below lists some of the commonly used materials. Acrylonitrile-Butadiene-StyreneABS Polyamide–(Nylon)NylonPA PolycarbonatePC Polypropene – (Polypropylene)PolypropylenePP PolystyreneGPPS Typical Products Produced Power-tool housingsSafety helmets Telephone handsetsTelevision cabinets Washing-up bowls Identifying Features Sprue marks, draw angles, mould split lines, ejection pins marks. Webs are used for strength. High quality finish Injection Moulding LECTURE 43

DTEL 10 Compression Moulding The Process The process requires plastic to be placed into a mould cavity where it is heated and plasticised. It is then compressed into shape by a heated punch. The materials used - melamine formaldehyde phenol formaldehyde urea formaldehyde. These materials can be formed into different shapes through applying both heat and pressure, other plastics do no have these properties. LECTURE 44

DTEL 11 Compression Moulding Uses Plastic products made using this process can resist temperature increases. Uses include camera cases, electrical wall sockets, handles, knobs and light switches. Identifying Features Walls of uniform thickness usually 3-6mm. Draft of 1° minimum required. Flashes on edges. Quality finish on female mould surface. LECTURE 44

DTEL 12 Extrusion The extrusion process is used for products with long uniform cross section. A variety of metals and thermo-plastics are suited to the extrusion process. pressure pad ram heated billet die die holder Forward Extrusion Used for long continuous lengths. A heated billet is forced through a die. Complex shaped dies can be used. Backward Extrusion Used for short lengths. A heated billet is extruded backwards by a smaller diameter punch. LECTURE 44

DTEL 13 Blow Moulding The Process The process is similar to injection moulding and extrusion. 1. The plastic is fed in granular form into a 'hopper' that stores it. 2. A large thread is turned by a motor which feeds the granules through a heated section. 3. In this heated section the granules melt and become a liquid and the liquid is fed into a mould. 4. Air is forced into the mould which forces the plastic to the sides, giving the shape of the bottle. 5. The mould is then cooled and is removed. LECTURE 45 Blow moulding

DTEL 14 Typical Materials Used Polyethylene (Low Density) LDPE, LLDPE PolypropylenePP Polyethylene - Terephthalate PET Polyvinyl chloridePVC Polyethylene (High Density) HDPE Typical Products Produced BottlesJars Roll-on containers Softened thermoplastic is forced on to the mould surfaces using compressed air. There are several variations of the process, producing articles of different sizes. The finish is never of the same standard as that of injection moulding but good mould enables products of uniformed thickness, complex shape and good quality to be produced. Blow moulding is fast and the process involves very little waste. Injection Blow Moulding LECTURE 45

DTEL 15 LECTURE 46 The Machine CALENDERING

DTEL 16 LECTURE 47 TYPICAL CALENDAR LINE

17 Coating and Impregnating Fabrics Industrial process used to produce: – Car tires – Conveyer belts – Inflatable rafts – Waterproof cloth tents – Rain coats LECTURE 47DTEL 17