Manufacturing of Plastic Components & Polymer Composites
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Manufacturing of Plastic Components & Polymer Composites
- 1. MANUFACTURING OF PLASTIC COMPONENTSMANUFACTURING OF PLASTIC COMPONENTS andand COMPOSITE MANUFACTURINGCOMPOSITE MANUFACTURING ( Mechanical Engineering / Special Machines / Unit 1)( Mechanical Engineering / Special Machines / Unit 1) v Plastic Components v Processing of Plastics v Composite Manufacturing Prepared by Dr.S.Cartigueyen, M.Tech., Ph.D
- 2. v PLASTIC COMPONENTS q PLASTICS - Synthetic Organic Materials. Made up of thousands of small molecules of O2, C, H2, N2 and other elements. Also called ‘ POLYMERS’ - Widely used in every day’s life. Very much used in Engineering field. - Plastic Products are formed by ‘Moulding, Casting or Extrusion’. Classification of Plastics o Thermoplastics o Thermosetting Plastics o Engineering Plastics o Thermosets o Elastomers o Composites o Structural Foam o Liquid Crystal Polymers 2Dr.S.Cartigueyen
- 3. PLASTICS … q Thermoplastics § Linear polymers. Their molecules are arranged in the shape of long thread. § It can be softened by heating and hardened by cooling. § It can be re-moulded. Examples: PVC, Polyster Uses: Insulating tapes, Toys q Thermosetting Plastics § Cross linked polymers. § It cannot be softened on heating. § Once hardened and set permanently. § It cannot be re-moulded. Examples: Epoxy resin, Duroplast Uses: Automobile parts, Electric plugs 3Dr.S.Cartigueyen q Thermoplastics q Thermosetting Plastics
- 4. Dr.S.Cartigueyen 4 q Engineering Plastics v Plastics which have the combination of various properties such as Toughness, Rigidity, Wear resistance, Heat resistance, Chemical resistance, Stiffness, High strength-weight ratio etc. (a) Engineering Thermoplastics o Celluloses : Prepared from various treatments of wood fibers and cotton. Good strength, chemical resistance and easy mouldability. Uses: Toys, Handles, Electrical parts, Spectacle frames, Fabric coatings etc. o Nylons (Polyamides) : Strong, tough and light weight. Low resistance to heat, abrasion and chemicals. Uses: Rope, sheets, bearings, gears, brush bristles etc. o Polyethylene Resins : Produced in low, medium and high density. High toughness, chemical resistance, electrical resistance and low cost. Uses: House wares (bowls/plates/bags/tubes/handles/brush/etc) o Polystyrene : Crystal clear, odorless, excellent tensile strength, used up to 90ºC. Uses: Bottles, utensils, toys etc. o Polypropylene : Excellent insulator, Easily moulded / extruded into any form. Uses: Automobile pedals, hospital equipments.
- 5. Dr.S.Cartigueyen 5 o Polycarbonate : Trade name – LEXAN. Keeps toughness at high temperature. Uses: Household articles, bathroom fittings and power tools. o Vinyl Plastics or PVC : Clear, transparent, easily coloured, high chemical resistance, very water repellant. Uses: Wire insulator, pipes, gaskets, tents, tarpaulin type covers. (b) Thermo Setting Engineering Plastics o Epoxy Resins : New comer in Plastic field. By adding hardener, it becomes more HARD. Good chemical resistance, electrical resistance, toughness, flexibility and stands up to 260ºC. Uses: Aircrafts and home appliances, electrical fittings, pipe fittings, printed circuit boards and boat bodies. o Amino Resins : (Urea + Melamine) Very hard, scratch resistance, water resistance, better electrical insulator. o Phenolics : (Phenol + Formaldehyde) Widely called BAKELITE. Hard, heat resistance. Low cost, excellent insulator, stands up to 260C. Uses: Coatings and adhesives. o Silicones : Produced by chemical formation of organic/inorganic materials. It is a transparent material. Used in industry as greases, oils, adhesives and rubber components. Uses: Gears, furniture, automobile parts, shoes, glass and silver polishing.
- 6. Dr.S.Cartigueyen 6 q Thermosets - Mixture of small reactive molecules. Most like fillers or fibers are added to reduce cost, modify physical properties/ shrinkage. - Improve flame resistance, dimensional stability, thermal stability, chemical resistance and Electrical properties. Examples : Epoxy, Phenolic, Unsaturated polyster, Polyurethane, acrylate etc. q Elastomers - Word derived from ‘ELASTIC’. They are polymers that have ‘high elasticity’. - Generally called ‘RUBBER. Natural rubber is the best known Elastomer. - Elastomers have a structure of less tightly bound molecules. - They are generally ‘Thermosets’ but may also be ‘Thermoplastic’. Examples : Unsaturated rubber, Natural rubber, Butyl rubber. Applications : Gaskets, Oil seals, O-rings, Pedals, Mattresses, Insulating materials.
- 7. Dr.S.Cartigueyen 7 q Composites - Made up of two or more materials to form a new material with enhanced material properties. Examples : Wood, Concrete, Brick. Fibrous composites : which consists of fibers in a matrix. Laminated composites : which are made of layers of various materials. Particulate composites : which are composed of particles in a matrix. q Structural Foam - Foam (pores) that is formed by trapping pockets of gas in a solid or liquid by adding chemical substance (foaming agents). - Structural foam is more elastic and used as heat / electrical insulating materials. - Urethane, Polypropylene, Phenolic, Silicone and Epoxy are the plastics used for making structural foam. Solid foam : Bath sponge, rubber Liquid foam : Used in fire extinguisher Synthetic Foam : Arm rest, shoe soals. Applications : - Mattresses, Automobile dash boards, Seat Cushion, TV cabinets, Speakers, Toys, Computer housing, etc.
- 9. Dr.S.Cartigueyen 9 q Factors Influencing the Selection of Plastics 1. Mechanical properties - Strength, stiffness, fatigue, toughness, ductility. 2. Degradation (Aging) - Brake down of chemical structure by heat, stress, radiation etc. - To prevent degradation, ‘Stabilizers’ are added with polymers. 3. Wear resistance and Frictional properties 4. Special Properties - Chemical stability, thermal/electrical Insulator, colour variant, transparent /opaque - High strength & low weight , good shock resistance etc. 5. Cost - Low cost of production and processing. 6. Processing methods - Easy to manufacture (any shape and size). - High accuracy of product size.
- 11. Dr.S.Cartigueyen 11 q EXTRUSION - Thermoplastics are ejected out through a die opening in continuous manner. - Used for production of sheets/tubes/ropes & further treated to get the final products. Raw materials: Powder of Vinyl resins, Cellulose, Nylon, Polyethylene etc. Types : 1. Single screw extruder 2. Twin screw extruder (a) Single screw Extruder - It has Three Zones : Feed Zone, Compression Zone, Metering Zone. - The machine heats the plastic raw material (e.g. PVC) to its melting point, after which it is pushed through a die that gives the material its shape. - When the extruded part comes out of the die, it is cooled. Advantages - Low tooling cost - Higher production rate - Simple process control - Complicated shapes can be produced - Thickness of product can be accurately maintained.
- 13. Dr.S.Cartigueyen 13 Single screw Extruder q Cross -section of Single and Twin screw Extruder barrel
- 14. Dr.S.Cartigueyen 14 q INJECTION MOULDING - Polymer is heated to highly plastic state and forced to flow under high pressure into a mold cavity, where it solidifies. - Produces discrete components that are almost always net shape and molded part, called a molding. Production cycle time is typically in the range 10 – 30 seconds. - Complex and intricate shapes can be produced. High production rate. - Used for making cups, toys, knobs, handles, plumb fittings, mobile phone body etc - Raw Materials : Pellets, Granules, Powders, Rod or Tube, Liquid plastics. - Figure shows the major parts of a typical Injection moulding machine. Types of Injection Moulding 1.Plunger type IM 2. Screw type IM 3. Structural foam IM 4. Sandwich Moulding 5. Gas Injection Moulding
- 16. Dr.S.Cartigueyen 16 Reciprocating Screw type Injection moulding… Typical Injection Moulding Cycle
- 17. Dr.S.Cartigueyen 17 q STRUCTURAL FOAM INJECTION MOULDING - Structural foam is a composite material produced when a polymer (thermoset / thermoplastic), is combined with either an inert physical gas, such as nitrogen, or a chemical blowing agent during the moulding process. - Plastic pellets are fed into the screw type injector through a hopper. - Pellets are melted by heating the injection chamber. - Nitrogen gas is supplied to the molten plastic and mix together. - This mixture is pumped into the accumulator. Pressure in accumulator is increased and forced into the mould cavity. Structural Foam Injection Moulding
- 19. Dr.S.Cartigueyen 19 q SANDWICH MOULDING - Sandwich moulding is defined as two or more polymers are injected one after the other through the same gate in one or more cavities. It is also called co- injection moulding. - Sandwich injection moulding used for geometrically simple parts to achieve specific product properties like low weight combined with high strength. Similar to air injection moulding, though instead of air, another plastic is injected. Advantages - Material, weight and cost is saved. - Increased stability and strength. - Decorative effects. - Combination characteristics. - Complex shapes can be made. Limitations - Slow Process Applications - Dishes, Handles, Container caps, Fittings, - Washing M/c parts - Electrical & Electronic components , etc.
- 23. Dr.S.Cartigueyen 23 q ROTATIONAL MOULDING - Rotational moulding is a unique plastic moulding process used primarily to create seamless, stress-free, hollow one-piece items. Similar to centrifugal casting. - Also called ‘Rotomoulding’, it is a high temperature, low pressure manufacturing method that combines heat and bi-axial rotation. - The process of rotational moulding begins with filling a hollow mould with a quantity of powder resin (polymer and/or other compounds). - The mould is then heated at high temperatures in an oven and bi- axially rotated as the polymer melts and coats the inside of the mould. - After the melting has been consolidated to the desired level and the timing is right, the mould is removed from the oven and cooled. Stages in Rotational Moulding
- 26. Dr.S.Cartigueyen 26 q INJECTION MOULDING OF THERMOSET MATERIALS - In thermoset injection molding, cold material is injected into an extremely hot mold to create a part. This process cures the part so it can never be melted again. - In thermoplastic injection molding, plastic material is melted and injected into a mold to create a part. - Injection moulding of thermoset plastic is similar to the process followed in Thermoplastic. The only difference is , water cooling is not necessary in thermoset materials. Because of ‘setting’ nature , thermoset plastics gets solid shape and taken out from mould. Advantages - Fastest cycle. - Efficient pre heating material - Easiest finishing - Mould cost is low.
- 27. Dr.S.Cartigueyen 27 q DESIGN CONSIDERATIONS FOR PLASTIC COMPONENTS 1) Avoid under cuts. 2) Provide shrinkage allowance. 3) Avoid sharp corners. 4) Long cored holes should be avoided. 5) Maintain uniform wall thickness 6) Try to design projections to have circular cross sections 7) Use suitable size inserts 8) Considered material properties. 9) Ribs provided for increase strength 10) Location of the parting surface of the mould should be in one plane 11) Avoid very thick sections 12) Avoid large flat surfaces. 13) Allow a minimum taper of 2º for easy removal from the mould. 14) Adopt cost - saving hole design ( use of core for holes)
- 28. Dr.S.Cartigueyen 28 v COMPOSITE MANUFACTURING - A combination of two or more materials to form a new material with enhanced material properties. Examples : Wood, Brick, Concrete - Composites are typically designed with a particular use in mind, such as added strength, efficiency or durability
- 29. Dr.S.Cartigueyen 29 Composite Manufacturing… Characteristics of Composite Manufacturing - Good bonding between fibers and matrix - Proper orientation of the fibers - Uniform distribution - Good dimensional control - High strength and stiffness on weight basis - High Specific strength (ratio of tensile strength to specific gravity) - High Specific modulus - Improved hardness Applications of Composite Materials • Automotive applications • Aerospace applications • Marine applications • Construction applications • Sanitary applications • Building /Sports applications and etc Advantages of Composite Materials - Light weight - High strength - High stiffness - High corrosion resistance Limitations of Composite Materials - Low ductility - More expensive - Difficult in manufacturing - Slow manufacturing process
- 30. Dr.S.Cartigueyen 30 q POLYMER MATRIX COMPOSITES - Polymer matrix composites (PMCs) are materials that use a polymer based resin as a matrix material with some form of fibres embedded in the matrix, as reinforcement. - The primary reason for using polymers is because of weight saving for their relative stiffness and strength. Fibers increase the modulus of the matrix material. - Both thermosetting and thermoplastic polymers can be used for the matrix material. Thermosetting resins widely used in Polymer composites. - Fiber reinforced polymer (FRP) is a composite material that consists of a polymer matrix embedded with high-strength fibers, such as glass, aramid, and carbon. Moulding processes are commonly used for Polymer composites with particles and chopped fibers. - Fiberglass is a reinforced plastic material which is composed of a woven material that is embedded with glass fibers. Fibreglass is combined with resin to form an extremely strong and durable composite. - It is a low cost composite material in a polymeric matrix .
- 31. Dr.S.Cartigueyen 31 q GLASS FIBERS MANUFACTURING PROCESS - Glass fiber manufacturing is the high-temperature conversion of various raw materials (predominantly borosilicates) into a homogeneous melt, followed by the fabrication of this melt into glass fibers. - Glass fiber production can be segmented into 3 phases: Phase 1. Raw materials handling, Phase 2. Glass melting and refining, and Phase 3. Wool glass fiber forming and finishing Raw materials : Silica sand, Boric acid , Minor ingredients (clay, coal) Types : (a) Direct melt process (b) Marble remelt process
- 32. Dr.S.Cartigueyen 32 Glass Fibers Manufacturing Process… (1) Direct Melt Process - The raw materials in solid form are mixed together and melted in a furnace and refined further. -The molten glass in the furnace goes directly to the filament formation (bushing). - The bushing serves as collector for the molten glass. - It is heated slightly to keep the glass at the correct temperature for fiber formation.
- 33. Dr.S.Cartigueyen 33 Glass Fibers Manufacturing Process… (2) Marble Remelt Process - Similar to direct melt process. - The only difference is, the molten glass is sheared and rolled into marbles. - After cooling the glass fiber marbles are packaged. - They are then remelted in marble bushing. - After the initial process of melting glass and passing it through filament formation, the fibers of glass are manufactured by two different methods such as, (a) Continuous filament method and (b) Staple fibers method
- 34. Dr.S.Cartigueyen 34 Glass Fibers Manufacturing Process… (a) Continuous Filament Process - In this process, continuos filaments of indefinite length is produced. - The molten glass passes through spinnerets having hundreds of small openings. - This process draws out the fibers in parallel filaments , a binder (sizing) is applied to facilitate the twisting and winding process. - The sizing is removed through volatizing in an oven. - Winding then takes place at around 1000 m/min speed. Advantages of Glass Fiber - Useful for thermal insulation - Glass has an amorphous structure (properties are same along the fiber & across the fiber) - Light weight but very strong Limitations of Glass Fiber - Glass fiber has no true melting point in pure form - Limited to service temperature below 200ºC - At higher service temperature, deterioration takes place Uses of Glass fiber - Thermal insulator (known as glass wool) - Good reinforcing agent for many polymer products. - Many sports items, automobile body, aircraft, boat hulls, tank vessels etc are made from glass fiber.
- 36. Dr.S.Cartigueyen 36 Hand Laminating Process… Advantages - Simple process - Low cost & more effective - No high temperature and no heavy pressure Disadvantages - Time consuming - Not suitable for mass production - Usefulness of this process depends on the skill of the processor. Applications - Boats, Tanks, - Bath ware - Housings - Truck/Auto components - Architectural products Stages in Hand Laminating Process
- 37. Dr.S.Cartigueyen 37 q AUTOCLAVE PROCESSING - Autoclave is a pressurized oven or vessel used to process parts and materials which require exposure to elevated pressure and temperature. - It is a process mainly utilized in the field of aviation as it guarantees the highest quality for composite structures. -The manufacture of high-performance polymer based composite materials often requires autoclave processing in order to increase the fiber to resin ratio. In addition, vacuum is also applied to suck volatile matters and entrapped air or gases. - The autoclaving process brings the individual prepreg (pre- impregnated material) plies together and consolidates them through pressure into a uniform solid material. - Elevated temperatures are necessary to initiate and complete the curing reaction for polymer based prepregs. Types of autoclaves 1. Autoclave pressurized with steam 2. Autoclave using heated gas (vacuum bag) Processing Steps
- 39. Dr.S.Cartigueyen 39 q FILAMENT WINDING PROCESS - This process is employed for fabrication of a continuous fiber reinforced composite structure having an axis of revolution. - Continuous fiber strands or rovings are first coated with resin in a resin bath and then fed through rollers to squeeze out excess resin and finally wound, under constant tension, around a collapsible mandrel. -There are basically two types of filament winding patterns: helical winding and biaxial winding. After winding is complete, the mandrel is removed from the carriage and placed in an oven, if required, for curing.
- 41. Dr.S.Cartigueyen 41 q PULTRUSION PROCESS - In this continuous fiber strands taken from a number of spools are sequentially pulled through a resin bath, a shaping guide and a hot die. - The fibers are coated in the resin bath and the excess resin is squeezed out. - The shaping guide provides a gradual change from a simpler to a more complex pre-formed shape close to that of the pultruded part. -The final shape is realized when the preformed shape is pulled through a hot die and gets cured. - Continuous strand mats and woven fabrics can also be pulled along with filament strands to provide better transverse properties to the pultruded sections. Stages of Pultrusion Process
- 42. Dr.S.Cartigueyen 42 Pultrusion Process… - Pultrusion process is same as metal extrusion process. - The only difference , the material is pulled through dies. Applications Components having continuous lengths, straight and constant cross sectional shapes such as beams, rods, tubes , channels, fiber sheets etc Disadvantages - Expensive die - Difficult to produce thin wall, tapered and complex shape products Advantages - Automated process - Continuous and high speed process - Rate of production is high Stages of Pultrusion Process
- 43. Dr.S.Cartigueyen 43 q LIQUID COMPOSITE MOULDING - Liquid composite molding (LCM) processes involve an impregnation of the reinforcement by a resin flow through the fabric. Liquid state matrix material (epoxy resin) is forced into the dry preformed reinforcing material (carbon fiber fabrix). - LCM consists of a variety of composite manufacturing processes such as 1. Resin transfer moulding (Flexible, Continuous, High speed, Vacuum-assisted) 2. Resin infusion moulding process (vacuum) 3. Injection compression moulding - The dry reinforcement, or preform, is enclosed in some form of mould, which fully defines the shape of the part. - Resin flows under pressure through the porous preform, expelling all air. - At some stage resin cure is initiated, and the mould is opened once the part has achieved significant rigidity. - Resin transfer moulding uses positive operating pressure, while in vacuum infusion the pressure is lower than the atmospheric pressure level.