BAKELITE PLASTICS -the beginnings

Post 583 by Gautam Shah

Clay was the first plastic material that could be formed to desired shape. Clay gains ‘plasticity-a moulding or shaping capacity, due to its grain shape, size and distribution and addition of water. A natural metal nodule or a purified one from the ore, on heating becomes, ‘plastic’. This property was not available with materials like wood and stone. Materials like Bamboo or Cain, have the capacity to bend, but cannot be reshaped or moulded. Plasticity is the property of material to be deformed repeatedly without rupture by the action of a force, and remain deformed after the force is removed.

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Potters clay > Wikipedia image by Yann

Historically few natural materials that exhibited the plastic behaviour were known, but without clear perception of the categorical behaviour. These natural materials were organic polymers or bio-derived materials such as egg and blood proteins. In 1600BC. Mesoamericans used natural rubber for balls, bands, and figurines. Treated Cattle’s horns were used for their translucency in lanterns and windows. Materials with similar properties were developed by treating casein -a milk-protein with lye. Casein was also used as gum material. Bitumen was used as a water proofing material for boats and also as a joint material for masonry. Plant-based starch materials on being cooked showed flow-behaviour. Lac, an insect exudate was used as gum or joining material in India. The lac was used for cast mouldings since 1868. Rubber, a plant exudate was used since 1535, as water proofing material and for shoe making.

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Cattle horn spectacles > Wikipedia image by Daderot

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Bakelite body Radio at Bakelite Museum > Wikipedia image by Robneild at en,wikipedia

Polymers were not distinctly identified till around 1900s, however during 1860s Thomas Graham noted that some dissolved organic compounds -typically cellulose, cannot be purified into a crystalline form. This was different organization of matter. Graham called them ‘colloids’, after the Greek word for glue =kolla. This was the beginning of the Age of Plastics or Polymer Age. (Plastic =plastikos Gk = mouldable) (Poly+mer=many molecules).

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Parkesine (London) developed the first plastic from plant origin cellulose by reacting it with nitric acid, to form a cellulose nitrate. Celluloid was plasticized with camphor, dissolved in alcohol and hardened into a transparent elastic material. On heating it could be moulded and coloured with pigments. It was a substitute material, for than (1860) widely used ivory balls for billiards. The product was patented under the trademark Celluloid. It was also used later in the manufacture of objects ranging from dental plates to men’s collars. Celluloid, despite its flameability and capacity deteriorate when exposed to light, was commercially successful.

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Ericsson Bakelite phone > wikipedia image by Holger.Ellgaard + sjalv laddat upp

The first totally synthetic plastic was the phenol-formaldehyde resin, Bakelite. In the early 1900s, Bakelite, the first fully synthetic thermoset, was reported by Baekeland. Baekeland’s was looking for a replacement for shellac that had difficult supply. And that is the reason, their first product a soluble phenol-formaldehyde like shellac was called ‘Novolak. Baekeland also worked on a process to strengthen wood by saturating it with a synthetic resin of phenol and formaldehyde.

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Bakelite chips colour chart 1924 > Wikipedia image

Baekeland reacted Phenol with Formaldehyde (an exothermic reaction) but stop the reaction midway, while the product was in liquid state (called A stage). ‘ The A resin (Resol) could be made directly into a usable plastic, or it could be brought to a solid B stage (Resitol) in which, though almost infusible and insoluble, it could still be ground into powder and then softened by heat to a final shape in a mould. Both stages A and B could be brought to a completely cured thermoset C stage, by heating under pressure. This last stage was Bakelite C, or true Bakelite.’
In 1927 the Bakelite patent expired and the market were flooded with competitive thermo setting resin products of Urea and Melamine formaldehyde, and other new thermoplastic resins such as cellulose acetate, polyvinyl chloride, poly-methyl methacrylate, and polystyrene.

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Bakelite, was recognized as the ‘National Historic Chemical Landmark’. Bakelite was mouldable material with electrical non-conductivity and heat-resistance properties. He saw a wide variety of uses of the resin with many different filling materials such as cotton, powdered bronze, slate dust, wood and asbestos fibres. It was used widely in electrical appliances replacing bulky ceramic components. It was used for kitchen handles, radio and telephone casings, kitchenware, jewellery, pipe stems, toys etc. His one of the first patents describes ‘Method of making insoluble products of phenol and formaldehyde’. Bakelite Company began to produce many material forms, but laminating varnish, was most successful products. Laminating varnishes are used for coating copper circuits, paper, fabrics and for manufacturing laminate sheets. Blocks or rods of transparent cast resins, known as artificial amber, that could be machined or carved to shapes were used for pipe stems, cigarette holders and jewellery.

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Old style vacuum cleaners with Bakelite body > Wikipedia image by Rosebud23

Baekeland’s heat and pressure patents expired in 1927 soon placing the company under severe pressure from competitors like Catalin. Catalin is also a phenol formaldehyde resin, but produced by a different, two-stage process. It was produced without any fillers like sawdust or carbon black. It can be worked with nominal carpentry tools like files, grinders and cutters, and polished to dull gloss. Another advantage of it was its transparency and capacity to take bright colours.

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Colourful buttons made of Catalin of 1930s > Wikipedia image attribution: Chemical Heritage Foundation

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VINYL RESINS

Post 559 by Gautam Shah

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Vinyl is a synthetic or man-made material. In chemistry, vinyl or ethynyl is the functional group. Vinyl groups can polymerize with the aid of a radical initiator or a catalyst, forming vinyl polymers. Vinyl polymers are of many types, all made from monomers in which one or more of the hydrogen atoms of ethylene are replaced by another atom or groups of atoms. One of the hydrogen atoms is replaced to produce Polypropylene, Polystyrene and Polyvinyl chloride. Two of the hydrogen atoms are replaced to produce Poly-isobutylene (a type of rubber) and Polymethyl methacrylate. And when both carbons are substituted, it produces a complex polymer, Polytetrafluoroethylene (DuPont –Teflon).

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Vinyl LP records Wikipedia image by CFCF

Vinyl (V) as a term, coined by the German chemist Hermann Kolbe in 1851, derives from Latin word vinum = wine, because of its relationship with ethyl alcohol. Vinyl Chloride (VC) (chloroethene) CH2=CHCl is a gaseous chemical intermediate, a monomer, not a final product. It is composed of two simple building blocks: ethylene, from petroleum and chlorine a common sea water product. Due to its hazardous nature, no end products use vinyl chloride in its monomer form. In popular usage, the vinyl relates to polyvinyl chloride, basis for one of the world’s most versatile plastic material. Polyvinyl chloride is made by polymerization of the monomer vinyl chloride (chloroethene) CH2=CHCl. Polyvinyl chloride (PVC) is very stable, storable, fine-grained white powder, and not as hazardous as its monomer. Compared with other plastic materials of vinyl formulations use substantial proportion of natural resources, with low energy requirements for processing and release low quantity of emissions.

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PVC buckets Wikipedia image by Goolawfredment

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Bright multi-coloured water pots of Chennai Flickr image by McKay Savage

Vinyl polymers or Polyvinyl resins are the most common and comparatively less expensive thermoplastic. The properties vary with chemical structure, crystallinity molecular weight, additives and modifying agents. Vinyl resins are non-oxidizing, permanently flexible tough and durable. These are resistant to moisture and humidity. Vinyl resins are resistant to mild alkali, acid, alcohol, grease, oils and aliphatic hydrocarbons. Vinyl resins degrade upon prolonged exposure to heat, and UV light. The degradation products include HCl which accelerates further degradation, leading to unsaturated polymer structure that can get oxidized. This results in brittleness, loss of flexibility, discolouration. Presence of chlorine offers excellent flame retardant properties making it a choice product for electrical conduit and wiring requiring high resistance to ignition and flame spread.

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PVC Pipes New Guthrie theatre Minneapolis Wikipedia image by uberculture (Lic. cc-by-2.0) http://www.flickr.com/photos/uberculture/106597452/

Polyvinyl can be made flexible, rigid, semi-liquid, clear or colourful. PVC are of two main varieties: Rigid PVC is used in construction industry and for industrial components. Uses also include, siding, flooring, pipes, extruded sections for doors and windows and hardware. Flexible PVC is softer and pliable due to addition of plasticizes, typically like phthalates. The uses include trims, sheets, sheathing for electrical wires and cables, handrail tops, toys, water buckets, water hose pipes, vinyl music records, imitation leather (Rexine), signage, inflatable products, and rubber replacement applications. PVC resins are used for coatings for metal finishes, collapsible tube finishes, plastic (or Latex) paints, marine and food coatings mastic compounds and strippable coatings. Emulsions based on vinyl acetate are popular compared to many other latex type of paints. Vinyl acetate emulsions are odourless, dry rapidly, durable on outdoor faces and surfaces can be washed easily.

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PVC dust bin Wikipedia image by Joolz

Vinyl resins have TWO basic sets of product categories:

Polyvinyl acetate: It is a leathery colourless low temperature softening thermoplastic, with relative stability to light and oxygen. It is mainly used for water-based adhesives, binders (fabric printing) and emulsion paints.

Polyvinyl chloride: It is converted from monomer to a polymer PVC. The final product is in flakes or pellets form, which are used for product forming through solution, dispersion, injection moulding, and extrusion.

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PVC window unit Wikipedia image by Mfc3058

Other co-polymer variants include:

1. Carboxy modified Vinyl chloride and Vinyl acetate > Carboxyl modification makes it possible to formulate air drying metal coatings.

2. Epoxy modified Vinyl chloride and Vinyl acetate > Epoxy modification provides ability to cross-linked, with carboxy modified vinyl resins to achieve a thermosetting system. Such thermosetting systems have superior chemical resistance and toughness.

3. Hydroxy modified Vinyl chloride and Vinyl acetate > Hydroxy modification improves compatibility and adhesion, provides sites for cross linking.

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Wikipedia image by Asadabbas

Commercially several products of PVC are widely used.

Chlorinated polyvinyl chloride (cPVC) is a thermoplastic produced by chlorination of polyvinyl chloride (PVC) resin. Uses include hot and cold water pipes, and industrial liquid handling. cPVC is resistant to several acids, bases, salts, paraffinic hydrocarbons, halogens and alcohols, but not resistant to solvents, aromatics and some chlorinated hydrocarbons. It can carry higher temperature liquids than PVC. Due to its specific composition, dealing with cPVC requires specialized solvent cement. The cPVC capacity to bend, shape, and weld makes it suitable for many uses.

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Various thermoplastics pipes used in Ultra Pure water system Wikipedia image by Wikikart99

Various Thermoplastic Pipes used in ultra pure Water Systems polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), ethylene chlorotrifluoroethylene (ECTFE) and polytetrafluoroethylene (PTFE)

Unplasticized polyvinyl chloride (uPVC) has strong resistance to chemical or electrochemical effects, sunlight, and chances of oxidation from water. As this is lead and plasticizer free, is used for potable water supply pipes.

(Molecular) Oriented Poly Vinyl Chloride oPVC is a comparatively a new technology material. This molecular-oriented bi-axial high performance product offers very high strength with extra impact resistance.

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POLYCARBONATE

Post 480  by Gautam Shah

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Polycarbonate is a tough plastic valued for its transparency. It has very high impact resistance combined with light weight. It is, 1/3 the weight of acrylic, and 1/6 of glass. Acrylic is 17% stronger than glass, where as polycarbonate is nearly unbreakable, being 400 times stronger than glass. It is very ductile, self extinguishing and flame retardant plastic. It remains dimensionally stable in prolonged sunlight exposure. Polycarbonate is more expensive than Glass or Acrylic. It is recyclable and environmentally preferable to PVC. Polycarbonate is attacked by many organic solvents. It is also fairly expensive compared to other plastics.

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Polycarbonates were first discovered in 1898, but remained without commercial exploitation for 30 years. In the post war period research resumed in 1953, with Bayer patenting the first linear polycarbonate. One week after this GE USA independently synthesized a branched polycarbonate and filed a conflicting patent. After the patent priority resolution, Bayer began commercial production under the trade name Makrolon in 1958. and GE began production under the name Lexan in 1960. After 1970, the original brownish polycarbonate tint was improved to glass-clear.

Polycarbonate is a versatile plastic, which can be injection moulded, extruded, blow moulded and thermo formed. Unlike most thermoplastics, polycarbonate can undergo large plastic deformations without cracking or breaking. It can, as a result be reshaped at room temperature by using techniques for sheet metal working. This makes it valuable for model or prototype making applications. It can be joined mechanically, solvent bonded, and welded with skill. Virgin polycarbonate is the original polymer, whereas re-ground polycarbonate is waste that has been prilled or formed into pellets. The properties do not change much after such prilling.

Polycarbonate Police shields

Polycarbonate is an amorphous thermoplastic of long-chain linear polyesters of carbonic acid and dihydric phenols. They are called polycarbonate because functional groups of polymers are linked by carbonate groups. An amorphous (non crystalline) polymer has a glass like, transparent appearance due to the random orientation and intertwined nature of its molecules like spaghetti. Polycarbonate has a glass transition temperature of about 147 °C and so begins to soften gradually above this point. It begins to flow at about 155 °C. Working tools or forming nozzles are held at above 80 °C temperature to get a product with a clean surface. The toughest grades have the higher molecular mass, but are more difficult to process.

Twin wall Polycarbonate Sheet

Polycarbonate water bottle

The prime uses of Polycarbonate relate to its transparency, toughness, lightness of weight, and exterior durability. Some of the uses are unbreakable openings’ ‘glasses’, roof domes, greenhouse enclosures, police riot shields, vandal-proof light shields, partitions in taxis, non rattling ‘glass’ for bus and tram sliding windows, bullet and temper-proof covers for the valuables and exhibits. Its easy form-ability allows its use for transparent gift and jewellery boxes, utensil covers, bodies of gadgets like hair dryers, housing for electric meters, switch covers, funerary caskets, safety helmets, and computer parts.

Polycarbonate Greenhouse

Polycarbonate has excellent transparency, durability, and high a refractive index, and so is used to make eyeglasses. A thin polycarbonate formed to required curvature makes it very light in weight eyeglasses for spectacles. The clarity, scratch resistance and ability to take on transparent colours makes it suitable for inspection glasses in industries, air craft interior fittings, mines lights, high voltage switches, sockets, back-lit advertising display boards, see-through floors and bottom lit dance floors.

CDs and DVDs

During the last decade polycarbonate is being used for making CDs and DVDs. Polycarbonate like ABS plastic can receive sputter deposition or evaporation deposition of aluminium without the need for a base-coat. Polycarbonate composites are used for marine utilities like boats, frigates. The addition of glass fibres to polycarbonate increases the tensile strength, flexural strength, flexural modulus, and heat deflection temperature.

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POLYMERS -basics

POLYMERS -basics

Post 341 ⇒   by Gautam Shah 

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Polymers that we use in our day-to-day life are of Four types

  1. Plastics, which are relatively stiff at room temperature,
  2. Rubbers or elastomers, which are flexible and retract quickly after stretching,
  3. Fibers, which are strong filamentary materials,
  4. Coatings, have resins with qualities that are somewhere between a plastic and an elastomer.

Panton Chair

Polyester Threads

Elastomer Shoes

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Commercially available plastic raw materials can be categorized as:

Thermoplastics

Thermoset

Elastomers

Often some material combinations provide characteristics across these categories, giving very different properties and hence applications.

Packaging nuts from Thermoplastic starch

Properties of a polymer are altered substantially by inclusion of various substances. These are solids, rubbers, liquids and gases. These additive substances serve following functions.

1 Chain addition or curtailment

2 Fillers

3 Plasticizing and softening

4 Lubricants and flow promoters

5 Anti aging compounds

6 Flame retarding

7 Colourant

8 Blowing agents

9 Cross linking agents

10 Control of Ultra violet effects

Animal Protein Glue

Synthesized polymers arrived on the scene just before and after the world war II. Natural polymers, however, have been with us in plants, human and other beings body. The human body contains many natural polymers, such as proteins and nucleic acids. Cellulose is the structural component of plants.

Jelly -Alginate Polymer

Human body has nearly 100,000 different types of proteins, and all derived from only twenty amino acids. Starch is a carbohydrate found in cereal grains and potatoes, is a polymer made up glucose monomers. Glycogen, is a polymer, stored in the liver and skeletal muscle tissues, as an energy reserve in animals, similar to the starch in plants. Cellulose is most common organic polymer element. Cotton is one of the purest form of cellulose. Chitin, a natural polymer called polysaccharide is similar to cellulose. It is present in the cell walls of fungi. The nucleic acids as nucleotides form DNA and RNA. Natural rubber and Gutta-percha are plant exudate polymers.

Natural Latex Tapping

Natural polymers, derived from plant or animal sources, are of great interest in the bio-materials fields, such as tissue-engineering, bio-med transplants, medicines, eco-friendly products. Natural polymers have relevance as scaffolds on which to grow cells to replace damaged ones.

Objects made of natural polymer Chitosan

Three materials of natural origin, widely used, polymers are chitosan, collagen and alginate. The principal source of chitosan is shellfish waste and cell walls of fungi. Commercial uses include the making of edible plastic food wraps and cleaning up of industrial waste-water. Collagen is used for medical purposes and to produce gums. Alginate is refined from brown seaweeds. In extracted form it absorbs water 200-300 times its own weight. It is used as thickening agent in foods such as ice-cream and as an emulsifying agent.

Teeth impression in Alginate mould

Naturally available other polymers are: Shellac was used for sealing, lacquer coatings and as foundry casting binder, Casein derived from milk protein is used in distemper colour preparation, Bitumen were used for water proof coating and as a preservative.

Lac sealing wax

Synthetic polymers were initially conceived as replacement of natural polymers or polymer like materials. Gutta-percha was used for insulating electric cables, replaced by polyethylene and vinyls. Cellulose nitrate was conceived to replace ivory and shellac. Bakelite or Phenol formaldehyde, was used to replace wood.

Sutures made from polyglycolic acid are absorbable and will be degraded by the body over time.

Natural polymers are biodegradable. These materials are favoured for medical use, as they allow cell attachment and growth (as scaffolding) and are non-ionic and non-inflammatory. Many of these materials are highly porous and lightweight.

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ABS PLASTICS

Post 284 –   by Gautam Shah

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ABS (Acrylonitrile-butadiene-styrene) has been described as wonder or Industrial plastic. Styrene Acrylonitrile copolymers were available since 1940’s, but introduction of a Butadiene as a third component in the 1950s created a range of ABS plastics.

ABS high impact resistance cover

ABS polymers are not affected by water, salts, inorganic acids, food acids and alkalis, alcohols and animal, vegetable and mineral oils. ABS plastics are soluble in ketone, swell or soften in some chlorinated hydrocarbons, esters, aromatics and aldehydes.

ABS in home goods

ABS can be moulded, extruded, vacuum-formed, blow moulded, rotational moulded and chrome plated. Moulding at a high temperature improves the gloss and heat resistance; however, high impact resistance and strength, are available by moulding at low temperature. ABS plastics are used largely for mechanical purposes, they also have remarkable electrical properties that are fairly constant over a wide range of frequencies and unaffected by temperature and atmospheric humidity. ABS is damaged by sunlight, causing a widespread and expensive recall of automobiles in US history.

Automobile Interior trims of Plain and Chrome plated ABS

ABS is used for brief cases, suit cases, printer bodies, remote control bodies, television bodies, hair dryers, textile bobbins, toys including Lego and Kre-O bricks, plated car linings and trims, bumpers, bars, furniture, protective headgear, hardware, water-taps, sanitary ware, golf-club heads. ABS raw material colour is ivory to white, but can be pigmented. ABS plastic ground down to a dia. of less than one micrometer is used as the vivid colourant in some tattoo inks.

ABS LEGO bricks

Box Handle Isolated Luggage

Its glass transition temperature is 105 °C. ABS. It is amorphous and therefore has no true melting point. ABS can be used between -20 and 80 °C, though its mechanical properties vary with temperature. ABS plastics are self-extinguishing, but flammable at high temperatures. It melts, then boils, when its vapours may burst into flames. On burning ABS does not produce any organic pollutants except carbon monoxide and hydrogen cyanide.

Automobile parts

ABS is a Terpolymer (three-way polymer) made by polymerizing styrene and acrylonitrile in the presence of poly-butadiene. It is formed of a long chain of poly-butadiene crossed with shorter chains of poly-styrene-co-acrylonitrile, but in varying proportions (from 15-35% acrylonitrile, 5-30% butadiene and 40-60% styrene), to achieve quality variants. The Acrylonitrile imparts chemical resistance and surface hardness, Butadiene contributes the impact strength and over all toughness, and Styrene helps in processing. ABS combines the strength and rigidity of acrylonitrile and styrene polymers with the toughness of poly-butadiene rubber.

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PLASTICS -the beginnings

PLASTICS -the beginnings

Post 282 ⇒   by Gautam Shah  →

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Man had Clay as the first material that could be formed to desired shape. Clay gains ‘plasticity’ -moulding or shaping capacity, due to its grain shape, size and distribution and addition of water. A natural metal nodule or a purified one from the ore, on heating also became, ‘plastic’. This property was unavailable with materials like wood and stone. Materials like Bamboo or Cain, have the capacity to bend but cannot be shaped or moulded.

Plasticity of Clay

Historically there were few natural materials that exhibited the plastic behaviour. Bitumen was used as a water proofing material for boats and also as a joint material for masonry. Plant-based starch materials on being cooked showed flow behaviour.

Bitumen

A plastic material can ‘flow’, is ductile and so can be moulded or shaped, with application of pressure or heat. Plasticity is a property of material to be deformed repeatedly without rupture by the action of a force, and remain deformed after the force is removed. Materials commonly known as ‘plastics’ are polymeric compounds that show elastic and viscous components.

Natural Rubber

Several natural plastic materials were known from ancient times, but without clear perception of categorical behaviour. Lac, an insect exudate was used as gum or joining material in India. The lac was used for cast mouldings since 1868. Rubber, a plant exudate was used since 1535, as water proofing material and for shoe making. Cattle’s horns were used for Lanterns during middle ages, however, materials with similar properties of horns were developed by treating casein -milk-proteins with lye. Casein was also used as gum material. During 1851 Rubber was combined with sulphur to form Ebonite. Several natural oils, such as Linseed, Castor, etc., was polymerised to form longer chain products.

The development of plastics actually began with formation a cellulose nitrate plasticized with camphor, as a substitute material for than widely used ivory balls for billiards in 1860. The product was patented under the trademark Celluloid. It was also used later in the manufacture of objects ranging from dental plates to men’s collars. Celluloid was commercially successful, despite its flameability and capacity deteriorate when exposed to light. Cellulose used for manufacturing the Celluloid was of plant origin. The first totally synthetic plastic was the phenol-formaldehyde resin, Bakelite. Other plastics introduced during this period include modified natural polymers such as a rayon, made from cellulose products.

Bakelite

Bakelite electrical switches were part of early electrification. These were black to dark chocolate brown electrical switches mounted on ceramic base and had brass internal fittings. Bakelite was used for garment buttons, telephones and electric current proof handles. Celluloid films were part of early reels of movies. These were highly combustible and required extra ordinary protection in cinema projection rooms. Celluloid films were later replaced with polyester films. Celluloid white balls were used in Table tennis or ping-pong, as it was known in 1940-50s.

The development of plastics has evolved from the use of natural plastic materials such as shellac to chemically modified natural materials such as the Rubber, Nitrocellulose, etc. to completely synthetic materials such as Bakelite, etc. During 1800s, Goodyear developed a process of vulcanization of natural rubber, accelerating the development of plastics.

Natural Rubber crafts

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