Post 282 – by Gautam Shah
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.
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.
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.
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 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.