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Plastic processes

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This document discusses various plastic processes used in manufacturing. It begins with an introduction to polymers and thermoplastics versus thermosets. It then provides details on common plastic processing techniques like injection molding, extrusion, blow molding, and others. Specific plastic materials used in each process are identified. Secondary processes like welding and fabrication are also discussed. The document serves to outline the major industrial methods for producing plastic goods from raw polymers.

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Plastic Processes Alejandro Corredor – alejandrocorredor@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Brayan Casas – brayancasas@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Diego Gutiérrez – diegogutierrez@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Abstract The plastic play an important role in industry and everyday life of people, this because of that these materials are rather used for a lot of tasks, from acting as a container until be part essential of a machine. The plastic are different depending on your composition, process of manufacture and use. To develop the article, we will focus mainly on the different processes that produce these materials. Key Words Injection, polymers, plastics, extrusion, Moulding. Introduction A polymer is a useful chemical made of many repeating units. A polymer can be a three dimensional network, two-dimensional network or a one-dimensional network. Repeating units are often made of carbon and hydrogen and sometimes oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorous, and silicon. Polymers occur in nature and can be made to serve specific needs. Manufactured polymers can be three-dimensional networks that do not melt once formed. Such networks are called thermoset polymers. Epoxy resins used in two-part adhesives are thermoset plastics. Manufactured polymers can also be one-dimensional chains that can be melted. These chains are thermoplastic polymers and are also called linear polymers. Plastic bottles, films, cups, and fibers are thermoplastic plastics. [1]
Some types of plastic or polymers, can you find us in the next table: Plastic Characteristics / Properties ABS (Acrylonitrile-butadiene- styrene) Rigid, low-cost thermoplastic, easily machined and thermo-formed. Acetal Engineering thermoplastic with good strength,wear resistance, and dimensional stability. More dimensionally stable than nylon under wet and humid conditions. Acrylic Clear, transparent,strong,break-resistant thermoplastic with excellent chemical resistance and weatherability. CPVC (Chlorinated PVC) Thermoplastic with properties similar to PVC, but operated to a 40- 60°F higher temperature. Fiberglass Thermosetting composite with high strength-to-weight ratio, excellent dielectric properties and unaffected by corrosion. Nylon Thermoplastic with excellent impact resistance,ideal for wear applications such as bearings and gears; Self-lubricating under some circumstances PEEK (Poly-ether-ether-ketone) Engineering thermoplastic, excellent temperature resistance, suitable for continuous use above 500°F, excellent flexural and tensile properties. PET (Poly-ethylene- terephthalate) Dimensionally stable thermoplastic with superior machining characteristics compared to acetal. Phenolic Thermosetting family of plastics with minimal thermal expansion, high compressive strength,excellent wear and abrasion resistance and a low coefficient of friction. Used for bearing applications and molded parts. Polycarbonate Transparent,tough thermoplastic with high impact strength,excellent chemical resistance and electrical properties, and good dimensional stability. Polypropylene Good chemical resistance combined with low moisture absorption and excellent electrical properties. Retains strength up to 250°F. Polysulfone Durable thermoplastic, good electrical properties, operates at temperatures in excess of 300°F. Polyurethane Thermoplastic, excellent impact and abrasion resistance,resists sunlight and weathering. PTFE (Poly-tetra-fluoro-ethylene) Thermoplastic with a low coefficient of friction, withstands heat up to 500°F, inert to chemicals and solvents,self-lubricating with a low thermal expansion rate. PVC (Poly-vinyl-chloride) Thermoplastic, resists corrosive solutions and gases both acid and alkaline, good stiffness. PVDF (Poly-vinyl-idene-fluoride) Thermoplastic, outstanding chemical resistance,excellent substitute for PVC or polypropylene. Good mechanical strength and dielectric properties. Table1.Types of Plastic and its characteristics [2]
Development [3] Exist a lot of types of process to manufacturing the plastics and the polymers, then going to explain some of the most important and most known process of the industry around the world. The information about this process are divide in three parts:  Processing Thermoplastics  Processing Thermosets  Secondary Manufacturing Processes Processing Thermoplastics Blown Film The process involves extrusion of a plastic through a circular die, followed by "bubble-like" expansion. Materials Used: Mainly Polyethylenes (HDPE, LDPE and LLDPE) but a wide variety of other materials can be used as blends with these resins or as single layers in a multi-layer film structure. Products Produced: Industry packaging, consumer packaging, laminating film, barrier film, films for the packaging of medical products, agricultural film. Extrusion Blow Moulding The blow moulding machine is based on a standard extruder barrel and screw assembly to plasticise the polymer. The molten polymer is led through a right angle and through a die to emerge as a hollow (usually circular) pipe section called a parison. Materials Used: Polypropylene (PP), Polyethylene (PE), Polyethylene - Terephthalate (PET) and Polyvinyl chloride (PVC) Products Produced: Bottles and containers, automotive fuel tanks, venting ducts, watering cans and boat fenders. Extrusion Profiles & Sheet Is a widely used method of forming plastics materials. The plastic raw material is both melted and traversed along by the action of heated rotary screws. It is a continuous process and is thus able to manufacture long lengths of a product. This is ideal for such applications as pipes and gaskets.
Materials Used: HDPE, PVC and and PTFE filled PVC Products Produced: Land drainage tubing, animal feeding troughs, cable harness, door seals, light diffusers, electrical conduit and cable protector, rainwater pipes and guttering, dip tubes, gas pipes, water pipes, soil pipes and window, door and conservatory sections Injection Blow Moulding Injection blow moulding is used for the production of hollow objects in large quantities. The main applications are bottles, jars and other containers. The injection blow moulding process produces bottles of superior visual and dimensional quality compared to extrusion blow moulding. Materials Used: Polyethylene (Low Density) LDPE, (LLDPE), Polypropylene (PP), Polyethylene - Terephthalate (PET), Polyvinyl chloride (PVC), Polyethylene (High Density) HDPE) Products Produced: Plastic Bottles Injection Moulding Injection Moulding, along with extrusion ranks as one of the prime processes for producing plastics articles. It is a fast process and is used to produce large numbers of identical items from high precision engineering components to disposable consumer goods. Materials Used: Acrylonitrile-Butadiene-Styrene (ABS), Nylon (PA), Polycarbonate (PC), Polypropylene (PP) and Polystyrene (GPPS) Products Produced: Power-tool housing, telephone handsets, television cabinets, electrical switches, dvds, automotive bumpers, automotive dash boards, battery casings, syringes, drug inhalation units. Process Cooling The necessity to cool or chill plastics processing machinery is mainly related to thermoplastic materials. At room temperature thermoplastic materials are solid. In order to shape them they must first be heated to their molten temperature. When molten, they can then be manipulated to a new shape. When formed to their new shape they must then be cooled to solidify them.
Rotational Moulding Is a process used for producing hollow plastic products. By using additional post- moulding operations, complex components can be produced enabling the process to compete effectively with other moulding and extrusion practices. Rotational moulding differs from other processing methods in that the heating, melting, shaping, and cooling stages all occur after the polymer is placed in the mould, therefore no external pressure is applied during forming. Vacuum Forming The process involves heating a plastic sheet until soft and then draping it over a mould. A vacuum is applied sucking the sheet into the mould. The sheet is then ejected from the mould. In its advanced form, the vacuum forming process utilizes sophisticated neumatic, hydraulic and heat controls thus enabling higher production speeds and more detailed vacuum formed applications. Processing Thermosets Pultrusion The pultrusion process starts by pulling/drawing continuous reinforcements through a resin impregnation system. Each fibre is coated with a specially formulated resin; the process is controlled to ensure full “wetting out” of the fibre reinforcement. Excess resin is then removed to expel any trapped air and to compact the fibres. The coated fibres are passed through preforming guides to align reinforcement and preform the part to the desired shape before entering the heated die. The shape and dimensions of the end product are ultimately determined by the die cross section. The temperature of the die is carefully controlled to ensure that the composite is fully cured, the rate of reaction is controlled by heating and cooling zones in the die. Resin Transfer Moulding RTM is a low pressure moulding process, where a mixed resin and catalyst are injected into a closed mould containing a fibre pack or preform. When the resin has cured the mould can be opened and the finished component removed.
A wide range of resin systems can be used including polyester, vinylester, epoxy, phenolic and methyl methacylates etc, combined with pigments and fillers including aluminium trihydrates and calcium carbonates if required. SMC / DMC Moulding Manufactures of DMC/BMC compounds is a batch process. The ingredients, chopped glass fibres, resin, mineral fillers, catalysts and a mould release DMC Conduit Box agent are loaded into a special mixer. Output from the mixer is in a flock form which is subsequently extruded in a rope type extrusion. Manufacture of SMC is a continuous in-line process. The material is sheathed both top and bottom with a plastic film. A paste is prepared comprising resin, styrene, heat activating catalysts, inert fillers, release agents and thickeners. The paste is spread uniformly into an SMC Junction Box the bottom film. Chopped glass fibres are randomly deposited onto the paste. The top film is introduced and the sandwich is rolled into a pre-determined thickness. The sheet is allowed to mature for 48 hours. Secondary Manufacturing Processing Welding Plastic products cannot always be made in one piece. Design and tooling constraints sometimes make it more economical and/or advantageous to tool the product as two or more pieces. The choice of which method of joining ultimately depends on the parts material, geometry and size, process capability, volume and cycle time desired. Other considerations such as capital costs will have a bearing on the choice. Applications: Design and tooling constraints sometimes make it more economical and/or advantageous to tool the product as two or more pieces. Post moulding joining of the parts provides a means of achieving an end solution. Thermoplastic Fabrication Is a secondary manufacturing process which can be defined as the use and further modification of primary manufactured sheet, pipe, lining and moulded or formed profiles using compatible materials and welding methods to produce a final product or system which can be used in conjunction with or in isolation from non- thermoplastic materials in the provision of a service, facility, system or process in a diverse range of Industrial applications.
References  [1] American Chemistry Council, Plastic, The Basics: Polymer Definition and Properties. https://plastics.americanchemistry.com/Education- Resources/Plastics-101/The-Basics-Polymer-Definition-and-Properties.html  [2] Engineering Hand Book, Types of Plastics http://www.engineershandbook.com/Tables/plasticprops.htm  [3] British Plastics Federation, Processes to produce plastic http://www.bpf.co.uk/plastipedia/processes/default.aspx#secondaryprocessi ngfinishing

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Plastic processes

  • 1. Plastic Processes Alejandro Corredor – alejandrocorredor@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Brayan Casas – brayancasas@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Diego Gutiérrez – diegogutierrez@usantotomas.edu.co Student of Engineer Mechanic in Universidad Santo Tomas Abstract The plastic play an important role in industry and everyday life of people, this because of that these materials are rather used for a lot of tasks, from acting as a container until be part essential of a machine. The plastic are different depending on your composition, process of manufacture and use. To develop the article, we will focus mainly on the different processes that produce these materials. Key Words Injection, polymers, plastics, extrusion, Moulding. Introduction A polymer is a useful chemical made of many repeating units. A polymer can be a three dimensional network, two-dimensional network or a one-dimensional network. Repeating units are often made of carbon and hydrogen and sometimes oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorous, and silicon. Polymers occur in nature and can be made to serve specific needs. Manufactured polymers can be three-dimensional networks that do not melt once formed. Such networks are called thermoset polymers. Epoxy resins used in two-part adhesives are thermoset plastics. Manufactured polymers can also be one-dimensional chains that can be melted. These chains are thermoplastic polymers and are also called linear polymers. Plastic bottles, films, cups, and fibers are thermoplastic plastics. [1]
  • 2. Some types of plastic or polymers, can you find us in the next table: Plastic Characteristics / Properties ABS (Acrylonitrile-butadiene- styrene) Rigid, low-cost thermoplastic, easily machined and thermo-formed. Acetal Engineering thermoplastic with good strength,wear resistance, and dimensional stability. More dimensionally stable than nylon under wet and humid conditions. Acrylic Clear, transparent,strong,break-resistant thermoplastic with excellent chemical resistance and weatherability. CPVC (Chlorinated PVC) Thermoplastic with properties similar to PVC, but operated to a 40- 60°F higher temperature. Fiberglass Thermosetting composite with high strength-to-weight ratio, excellent dielectric properties and unaffected by corrosion. Nylon Thermoplastic with excellent impact resistance,ideal for wear applications such as bearings and gears; Self-lubricating under some circumstances PEEK (Poly-ether-ether-ketone) Engineering thermoplastic, excellent temperature resistance, suitable for continuous use above 500°F, excellent flexural and tensile properties. PET (Poly-ethylene- terephthalate) Dimensionally stable thermoplastic with superior machining characteristics compared to acetal. Phenolic Thermosetting family of plastics with minimal thermal expansion, high compressive strength,excellent wear and abrasion resistance and a low coefficient of friction. Used for bearing applications and molded parts. Polycarbonate Transparent,tough thermoplastic with high impact strength,excellent chemical resistance and electrical properties, and good dimensional stability. Polypropylene Good chemical resistance combined with low moisture absorption and excellent electrical properties. Retains strength up to 250°F. Polysulfone Durable thermoplastic, good electrical properties, operates at temperatures in excess of 300°F. Polyurethane Thermoplastic, excellent impact and abrasion resistance,resists sunlight and weathering. PTFE (Poly-tetra-fluoro-ethylene) Thermoplastic with a low coefficient of friction, withstands heat up to 500°F, inert to chemicals and solvents,self-lubricating with a low thermal expansion rate. PVC (Poly-vinyl-chloride) Thermoplastic, resists corrosive solutions and gases both acid and alkaline, good stiffness. PVDF (Poly-vinyl-idene-fluoride) Thermoplastic, outstanding chemical resistance,excellent substitute for PVC or polypropylene. Good mechanical strength and dielectric properties. Table1.Types of Plastic and its characteristics [2]
  • 3. Development [3] Exist a lot of types of process to manufacturing the plastics and the polymers, then going to explain some of the most important and most known process of the industry around the world. The information about this process are divide in three parts:  Processing Thermoplastics  Processing Thermosets  Secondary Manufacturing Processes Processing Thermoplastics Blown Film The process involves extrusion of a plastic through a circular die, followed by "bubble-like" expansion. Materials Used: Mainly Polyethylenes (HDPE, LDPE and LLDPE) but a wide variety of other materials can be used as blends with these resins or as single layers in a multi-layer film structure. Products Produced: Industry packaging, consumer packaging, laminating film, barrier film, films for the packaging of medical products, agricultural film. Extrusion Blow Moulding The blow moulding machine is based on a standard extruder barrel and screw assembly to plasticise the polymer. The molten polymer is led through a right angle and through a die to emerge as a hollow (usually circular) pipe section called a parison. Materials Used: Polypropylene (PP), Polyethylene (PE), Polyethylene - Terephthalate (PET) and Polyvinyl chloride (PVC) Products Produced: Bottles and containers, automotive fuel tanks, venting ducts, watering cans and boat fenders. Extrusion Profiles & Sheet Is a widely used method of forming plastics materials. The plastic raw material is both melted and traversed along by the action of heated rotary screws. It is a continuous process and is thus able to manufacture long lengths of a product. This is ideal for such applications as pipes and gaskets.
  • 4. Materials Used: HDPE, PVC and and PTFE filled PVC Products Produced: Land drainage tubing, animal feeding troughs, cable harness, door seals, light diffusers, electrical conduit and cable protector, rainwater pipes and guttering, dip tubes, gas pipes, water pipes, soil pipes and window, door and conservatory sections Injection Blow Moulding Injection blow moulding is used for the production of hollow objects in large quantities. The main applications are bottles, jars and other containers. The injection blow moulding process produces bottles of superior visual and dimensional quality compared to extrusion blow moulding. Materials Used: Polyethylene (Low Density) LDPE, (LLDPE), Polypropylene (PP), Polyethylene - Terephthalate (PET), Polyvinyl chloride (PVC), Polyethylene (High Density) HDPE) Products Produced: Plastic Bottles Injection Moulding Injection Moulding, along with extrusion ranks as one of the prime processes for producing plastics articles. It is a fast process and is used to produce large numbers of identical items from high precision engineering components to disposable consumer goods. Materials Used: Acrylonitrile-Butadiene-Styrene (ABS), Nylon (PA), Polycarbonate (PC), Polypropylene (PP) and Polystyrene (GPPS) Products Produced: Power-tool housing, telephone handsets, television cabinets, electrical switches, dvds, automotive bumpers, automotive dash boards, battery casings, syringes, drug inhalation units. Process Cooling The necessity to cool or chill plastics processing machinery is mainly related to thermoplastic materials. At room temperature thermoplastic materials are solid. In order to shape them they must first be heated to their molten temperature. When molten, they can then be manipulated to a new shape. When formed to their new shape they must then be cooled to solidify them.
  • 5. Rotational Moulding Is a process used for producing hollow plastic products. By using additional post- moulding operations, complex components can be produced enabling the process to compete effectively with other moulding and extrusion practices. Rotational moulding differs from other processing methods in that the heating, melting, shaping, and cooling stages all occur after the polymer is placed in the mould, therefore no external pressure is applied during forming. Vacuum Forming The process involves heating a plastic sheet until soft and then draping it over a mould. A vacuum is applied sucking the sheet into the mould. The sheet is then ejected from the mould. In its advanced form, the vacuum forming process utilizes sophisticated neumatic, hydraulic and heat controls thus enabling higher production speeds and more detailed vacuum formed applications. Processing Thermosets Pultrusion The pultrusion process starts by pulling/drawing continuous reinforcements through a resin impregnation system. Each fibre is coated with a specially formulated resin; the process is controlled to ensure full “wetting out” of the fibre reinforcement. Excess resin is then removed to expel any trapped air and to compact the fibres. The coated fibres are passed through preforming guides to align reinforcement and preform the part to the desired shape before entering the heated die. The shape and dimensions of the end product are ultimately determined by the die cross section. The temperature of the die is carefully controlled to ensure that the composite is fully cured, the rate of reaction is controlled by heating and cooling zones in the die. Resin Transfer Moulding RTM is a low pressure moulding process, where a mixed resin and catalyst are injected into a closed mould containing a fibre pack or preform. When the resin has cured the mould can be opened and the finished component removed.
  • 6. A wide range of resin systems can be used including polyester, vinylester, epoxy, phenolic and methyl methacylates etc, combined with pigments and fillers including aluminium trihydrates and calcium carbonates if required. SMC / DMC Moulding Manufactures of DMC/BMC compounds is a batch process. The ingredients, chopped glass fibres, resin, mineral fillers, catalysts and a mould release DMC Conduit Box agent are loaded into a special mixer. Output from the mixer is in a flock form which is subsequently extruded in a rope type extrusion. Manufacture of SMC is a continuous in-line process. The material is sheathed both top and bottom with a plastic film. A paste is prepared comprising resin, styrene, heat activating catalysts, inert fillers, release agents and thickeners. The paste is spread uniformly into an SMC Junction Box the bottom film. Chopped glass fibres are randomly deposited onto the paste. The top film is introduced and the sandwich is rolled into a pre-determined thickness. The sheet is allowed to mature for 48 hours. Secondary Manufacturing Processing Welding Plastic products cannot always be made in one piece. Design and tooling constraints sometimes make it more economical and/or advantageous to tool the product as two or more pieces. The choice of which method of joining ultimately depends on the parts material, geometry and size, process capability, volume and cycle time desired. Other considerations such as capital costs will have a bearing on the choice. Applications: Design and tooling constraints sometimes make it more economical and/or advantageous to tool the product as two or more pieces. Post moulding joining of the parts provides a means of achieving an end solution. Thermoplastic Fabrication Is a secondary manufacturing process which can be defined as the use and further modification of primary manufactured sheet, pipe, lining and moulded or formed profiles using compatible materials and welding methods to produce a final product or system which can be used in conjunction with or in isolation from non- thermoplastic materials in the provision of a service, facility, system or process in a diverse range of Industrial applications.
  • 7. References  [1] American Chemistry Council, Plastic, The Basics: Polymer Definition and Properties. https://plastics.americanchemistry.com/Education- Resources/Plastics-101/The-Basics-Polymer-Definition-and-Properties.html  [2] Engineering Hand Book, Types of Plastics http://www.engineershandbook.com/Tables/plasticprops.htm  [3] British Plastics Federation, Processes to produce plastic http://www.bpf.co.uk/plastipedia/processes/default.aspx#secondaryprocessi ngfinishing