Plastics: An Economical Synthesis of Aesthetics and Function
PLASTICS“An economical synthesis of aesthetics and function”
Introduction Plastic is the general common term for a wide range of synthetic or semi synthetic organic solid materials suitable for the manufacture of industrial products. Plastics are typically polymers of high molecular weight, and may contain other substances to improve performance and/or reduce costs. The word derives from the Greek (plastikos), "fit for molding", ]. It refers to their malleability, or plasticity during manufacture, that allows them to be cast, pressed, into an enormous variety of shapes—such as films, fibers, plates, tubes, bottles, boxes, and much more. India produces about 4.00 lac of tonnes per year.
Characteristics of Plastics Plastics are divided into two distinct groups: thermoplastics and thermosets. Thermoplastic-meaning that once the plastic is formed it can be heated and reformed repeatedly. e.g-Celluloid is a thermoplastic. This property allows for easy processing and facilitates recycling. Thermosets- can not be remelted. Once these plastics are formed, reheating will cause thematerialto decompose rather than melt. Eg.- Bakelite, poly phenol formaldehyde, is a thermoset. Plastics can be very resistant to chemicals.-some of solvents easily dissolve plastics, other plastics provide safe, non-breakable packages for aggressive solvents.
Plastics can be both thermal and electrical insulatorThermal resistance is evident in the kitchen with plastic pot and pan handles,coffee pot handles, the foam core of refrigerators and freezers, insulated cups,coolers and microwave cookware.The thermal jackets that many skiers wear is made of polypropylene and thefiberfill in many winter jackets is acrylic or polyester.
Generally, plastics are very light in weight with varying degrees of strength.Applications of plastics from toys to the frame structure of buildings, or from delicate nylon fiber , which is used in bulletproof vests.
•Plastics can be classified by their chemical structure, namely the molecular units that make upthe polymers backbone and side chains.•Common thermoplastics range from 20,000 to 500,000 in molecular mass, while thermosetsare assumed to have infinite molecular weight.• These chains are made up of many repeating molecular units, known as "repeat units", derivedfrom "monomers"; each polymer chain will have several thousand repeat units.•The vast majority of plastics are composed of polymers of carbon and hydrogen alone or withoxygen, nitrogen, chlorine or sulfur in the backbone.•Some plastics are partially crystalline and partially amorphous in molecular structure.•semi-crystalline plastics include polyethylene, polypropylene, poly (vinyl chloride),polyamides (nylons), polyesters and some polyurethanes.•Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methylmethacrylate), and all thermosets.
History The history of manufactured plastics goes back more than 100 years.Their usage over the past century has enabled society to make huge technological advances. Although plastics are thought of as a modern invention, there have always been "natural polymers" such as amber, tortoise shells and animal horns. Alexander Parkes unveiled the first man-made plastic at the 1862 Great International Exhibition in London. This material -- which was dubbed Parkesine, now called celluloid -- was an organic material derived from cellulose that once heated could be molded but retained its shape when cooled. Parkes claimed that this new material could do anything that rubber was capable of, yet at a lower price. He had discovered a material that could be transparent as well as carved into thousands of different shapes. In 1907, chemist Leo Hendrik Baekland, while striving to produce a synthetic varnish, stumbled upon the formula for a new synthetic polymer originating from coal tar. He subsequently named the new substance "Bakelite." Bakelite, once formed, could not be melted. Because of its properties as an electrical insulator Bakelite was used in the production of high-tech objects including cameras and telephones.
Plastics served as substitutes for wood, glass and metal during the hardship times of World War’s I & II. After World War II, newer plastics, such as polyurethane, polyester, silicones, polypropylene, and polycarbonate joined polystyrene and PVC in widespread applications. From daily tasks to our most unusual needs, plastics have increasingly provided the performance characteristics that fulfill consumer needs at all levels. Plastics are used in such a wide range of applications because they are uniquely capable of offering many different properties.
Raw materials Basic raw materials used in making of plastics are:1. Petroleum2. Lime stone3. Salt4. Sulphur5. Cellulose from cotton and wood6. Air7. Water8. Oil and natural gas.
Most plastics are made from crude oil (coal and natural gas can also beused), Crude oil is found deep underground and by drilling deep down intothe rock oil is brought to the surface and then shipped or piped from theproducing regions to refineries .The crude oil is then refined to make petrol, diesel and motor oils for carsand lorries. Out of every 100 litres of oil refined, 10 litres are used to makeplastic.To make plastics, the atoms that make up oil are pulled apart and separated.They are then joinedback together in long thin chains of atoms called polymers. By changing theorder ofthe atoms in the polymer chains, different kinds of plastic can be produced.Plastic is then moulded into thousands of different shapes. There are threemain ways ofmoulding plastic, by injection, heat or being blown. .
Process showing manufacturing of plastics from crude oil
Casting-mould of different materials such as lead –antimony ,sheet metal, clay or POP are used to cast plastics into required shape without application of any pressure.
Extrusion - Plastic pellets or granules are first loaded into a hopper, then fed into an extruder, which is a long heated chamber, through which it is moved by the action of a continuously revolving screw. The plastic is melted by a combination of heat from the mechanical work done and by the hot sidewall metal. At the end of the extruder, the molten plastic is forced out through a small opening or die to shape the finished product. As the plastic product extrudes from the die, it is cooled by air. water used for object and tubes.
Injection molding - In injection molding, plastic pellets or granules are fed from a hopper into a heating chamber. An extrusion screw pushes the plastic through the heating chamber, where the material is softened into a fluid state. Again, mechanical work and hot sidewalls melt the plastic. At the end of this chamber, the resin is forced at high pressure into a cooled, closed mold. Once the plastic cools to a solid state, the mold opens and the finished part is ejected.
Blow molding - Blow molding is a process used in conjunction with extrusion or injection molding. A chilled mold is clamped around the tube and compressed air is then blown into the tube to conform the tube to the interior of the mold and to solidify the stretched tube. Overall, the goal is to produce a uniform melt, form it into a tube with the desired cross section and blow it into the exact shape of the product. This process is used to manufacture hollow plastic products and its principal advantage is its ability to produce hollow shapes without having to join two or more separately injection molded parts
Types of plastics1. Polyethylene Terephthalate (PET or PETE)2. High Density Polyethylene (HDPE)3. Polyvinyl Chloride (PVC)4. Low Density Polyethylene (LDPE)5. Polypropylene (PP)6. Polystyrene (PS)7. Thermosets8. Thermoplastics9. Elastomers
ThermosetsThermosets are hard and have a very tight-meshed, branched molecular structure.Curing proceeds during shaping, after which it isno longer possible to shape the material byheating.Further shaping may then only be performed bymachining.Thermosets are used, for example, to make lightswitches.
ElastomersWhile elastomers also have a crosslinkedstructure, they have a looser mesh thanthermosets, giving rise to a degree ofelasticity.Once shaped, elastomers also cannot bereshaped by heating.Elastomers are used, for example, toproduce automobile tires.
ThermoplasticsThermoplastics have a linear or branchedmolecular structure which determines theirstrength and thermal behavior; they areflexible at ordinary temperatures.At approx. 120 - 180 C, thermoplasticsbecome a pasty/liquid mass. The servicetemperature range for thermoplastics isconsiderably lower than that for thermosets.The thermoplastics polyethylene (PE),polyvinyl chloride (PVC) and polystyrene(PS) are used, for example, in packagingapplications.
PETE Polyethylene Terephthalate (PET or PETE) is hard, tough and has good gas and moisture barrier properties making it ideal for carbonated beverage applications and other food containers. its high use temperature allows it to be used in applications such as heatable pre-prepared food trays. its heat resistance and microwave transparency make it an ideal heatable film. HDPE High Density Polyethylene (HDPE) is used for many packaging applications because it provides excellent moisture barrier properties and chemical resistance. General uses of HDPE include injection-molded beverage cases, bread trays as well as films for grocery sacks and bottles for beverages and household chemicals.
PVC Polyvinyl Chloride (PVC) has excellent transparency, chemical resistance, long term stability, good weatherability and stable electrical properties. Pvc products can be broadly divided into rigid and flexible materials. Rigid applications are concentrated in construction markets, which includes pipe and fittings, siding, rigid flooring and windows. PVCs success in pipe and fittings can be attributed to its resistance to most chemicals, imperviousness to attack by bacteria or micro-organisms, corrosion resistance and strength. It is used in wire and cable sheathing, insulation, film and sheet, flexible floor coverings, synthetic leather products, coatings, blood bags, and medical tubing.
LDPE Low Density Polyethylene (LDPE) is predominantly used in film applications due to its toughness, flexibility and transparency. LDPE has a low melting point making it popular for use in applications where heat sealing is necessary. LDPE is also used to manufacture some flexible lids and bottles, and it is widely used in wire and cable applications for its stable electrical properties and processing characteristics. PP Polypropylene (PP) has excellent chemical resistance and is commonly used in packaging. It has a high melting point, making it ideal for hot fill liquids. Polypropylene is found in everything from flexible and rigid packaging to fibers for fabrics and carpets and large molded parts for automotive and consumer products.
PS Polystyrene (PS) is a versatile plastic that can be rigid or foamed. General purpose polystyrene is clear, hard and brittle. Its clarity allows it to be used when transparency is important, as in medical and food packaging, in laboratory ware, and in certain electronic uses. Expandable Polystyrene (EPS) is commonly extruded into sheet for thermoforming into trays for meats, fish and cheeses and into containers such as egg crates. EPS is also directly formed into cups and tubs for dry foods such as dehydrated soups. Both foamed sheet and molded tubs are used extensively in take-out restaurants for their lightweight, stiffness and excellent thermal insulation.Other Plastics There are many other plastics beyond the most common ones described above, for example nylon, ABS copolymers, polyurethanes, and polymethyl methacrylate.
Environmental issues related with plastics Recycling of Plastics: It has been the most important issue today scenario because most of the plastics are non Bio-Degradable in nature .
Plastics are durable and degrade very slowly. In some cases, burning plastic can release toxic fumes. Also, the manufacturing of plastics often creates large quantities of chemical pollutants. Prior to the ban on the use of CFCs in extrusion of polystyrene (and general use, except in life-critical fire suppression systems; see Montreal Protocol), the production of polystyrene contributed to the depletion of the ozone layer; however, non-CFCs are currently used in the extrusion process. Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, though the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.
Air pollution:Some people try to dispose of unwanted plastic items by burning them on bonfires in the garden. However, burning plastics can create lots of choking black smoke which can pollute the air we breath. In a modern EfW incinerator plastics can be burnt without causing pollution as the smoke is filtered and cleaned before it is released into the air.
Uses of plastics Common uses of plastics Plastics versatility allow them to be used in everything from car parts to building construction. Plastics help make your life easier and better. Plastic is shatter-resistant. In each case, plastics help make your life easier, healthier and safer. They help major appliances - like refrigerators or dishwashers - resist corrosion, last longer and operate more efficiently. It helps save energy. In fact, plastics can play a significant role in energy conservation. Plastic bag manufacture generates less greenhouse gas and uses less fresh water than does paper bag manufacture.
Plastics as a Building MaterialToday, plastics materials are so widely used inthe building industry that it would be difficult toenvisage the construction of any building withoutthem.The Building and Construction sector -currentlysecond largest user of plastics in Europe -isexpected still to grow substantially in the future.Plastics have over the years become amaterial of choice for achieving economic andenvironmental balance between technologicalchallenges and functional design.
Plastics in Building and Construction applications plastics for decorative laminates plastics for drainage and irrigation pipes plastics for drinking water pipes plastics for electrics and electronics plastics for fittings plastics for floor and wall coverings plastics for insulation materials plastics for roofing plastics for sewer pipes and ducts plastics for waterproofing plastics for window and door profiles
Features and Advantages in Building and Construction durability, corrosion resistant cold, heat and sound insulation for energy saving and noise reduction cost efficiency light weight maintenance free innovation applications with unlimited choice of surface, colours and materials for creative design recyclability
Building with plastics saves energy and money, and protects the environment Plastics are a very important material in the building sector. In fact, roughly 20% of all the plastics used are used for products in the building industry. And after packaging, the building industry is the second highest user of plastics. Plastics are also very light and they require very little maintenance (they do not rust or rot). This makes them ideal for the construction industry. Housing is the second biggest consumer of energy. Plastics make great insulators and sealers which helps enormously in improving energy efficiency and reducing harmful C02 emissions.
Uses of plastics in Architecture On the basis of classification of plastics Polyethylene Terephthalate Because of its heat resistance capability & microwave transparency ,it is being used in roof making purposes
PolypropyleneThese are though materials used in fatigue resistance, chemical resistanceand electrical insulation properties.used as storage tanks,switches & seal ofdoors & windows
High Density PolyethyleneHigh density polyethylene sheets are similar to polypropylene sheets in termsof usability. It has a lower melting point & heats more uniformly.Used for storage tanks, industrial containers, fish boxes etc.Due to its flexibility & leak proof joints it is used over rough terrain.
Polystyrene The insulating ability of polystyrene prevents heat generated inside buildings makes it an ideal material for energy efficient building products particularly being soaked into the ground and is when combined with its other properties: particularly effective in improving the performance of under floor heating Sound absorbency which increases sound systems insulation particularly when used in In floor slab the system is completed by combination with harder building materials such as concrete; the placement of reinforcing bars between the blocks in both directions, EPS is non toxic, does not contain CFCs, reinforcing mesh above the blocks and can be 100% recycled, Versatile in that it concrete to fill the channels, encapsulate can be moulded, shaped and cut into the rebar and mesh to form the structure virtually any shape or pattern of the floor slab. Fire-retardant. All polystyrene used in building products is fire-retardant and will not propagate or contribute to the spread of fire
Low Density PolyethyleneLow Density Polyethylene (LDPE) is predominantly used infilm applications due to its toughness, flexibility and transparency.LDPE has a low melting point making it popular for use inapplications where heat sealing is necessary.LDPE is also used tomanufacture some flexible lids and bottles
Sprayed PolyurethaneIt is a type of plastic which is used on the roof to prevent it from leaking
ThermoplasticsAdvanced framing techniques Pultruded Glass Reinforcedcreate structurally sound buildings. PolyesterInsulation material to improvethermal resistance or R-value
Elastomers Mainly used in door, window and car to give airproof propertiesEPDM SealingStrip
PVC one the major components in Building construction PVC Properties for a Building Moisture proofing,corrosion-resistance and free from deformation; Multiple chamber system design ensure thermal and sound insulation,fire retardance. Galvanized steel reinforcement enhance high strength and stability for the window system Easy assemble, green environmental protection Glazing beads in various size are available to accommodate the different thickness of glass.
Roofline productsPVC does not warp or rot and is highly resistant, making it ideal for rooflinedrainage, cladding, fascias, soffits and bargeboards
GRP - Glass Reinforced Plastic GRP is a very high strength composite material made from plastic reinforced by fine fibres / strands of glass •Key Advantages; * Design flexibility - The material can be moulded into virtually any shape; * High strength impact resistant; * Vast range of RAL colours and textures available; * Ideal for internal and external use (material is water proof); * Fire retardant chemicals can be incorporated into the material; * Speed of installation; * Can be cost effective when manufactured in volume.
On the basis of applications in buildingsplastics for decorative laminates High Pressure Laminates for flooring & Counterparts
Plastics for drainage and irrigation pipes plastics for drinking water pipes
Plastics for electrics andelectronics & fittings
plastics for insulation materials Theses types of houses are: Fire-resistant, and wind- resistant. Also it is highly sound resistant, making for a peaceful home in even the busiest areas. Foam insulation form
Plastic Panels Plastic Panels for the Dairy Industryfor the Car Wash Industry
Exampleswalls of polycarbonate divide and define spaces in both houses. The degree of opacityare used to vary the effects of light and shadow.
216 Alabama and 1603 Random RoadNewyork,U.S.AArchitect: Dan Rockhill, Kent Spreckelmeyer, Studio804, Newyork,U.S.ALexan (polycarbonate) from GE Structural Plastics
The data centre at YouBet.com is enclosed by YouBet.comcurved acrylic panels fastened to the stud wall San Fernando Valley, Calif.with hat channel clips (below). Workstations Architect: Lorcan O’Herlihy Architects (Lorcan O’Herlihy,(right) are enclosed with single sheets of heated Plastics suppliers: Hastings Plasticsand bent acrylic (workstations); Fisher Lumber (curved wall); Crommie Construction (contractor)
By using green translucent polycarbonate on the exterior layer ofthe facade and white translucent polycarbonate on the interior, theeffect changes from inside to outside. Green Glen,San Francisco,Calif.Architect: Pfau Architecture(Peter Pfau, principal)
IBM E-business Center for InnovationChicagoArchitect: Design Office (George Yu and Jason King, principals), LosAngeles; Hellmuth, Obata, & Kassabaum, Chicago .NorthwesternTerrazzo & Flooring (acrylic terrazzo)
Acrylic terrazzo flooring (middleleft, bottom left) gives depth to floorsurfaces and reflects lightthroughout the space. Fiber resincoat closets and a reception deskenclosure, made by sameprocess, yield different effects whencompleted.