– WithContributions from Industrial Training Institute, Aundh Pune And Central Institute of Plastics Engineering & Technology (CIPET) India
Plastics are mostly derived from oil and natural gas. The major feedstock is oil. They are produced by a process which is known as polymerization, the chemical bonding of monomers into polymers. Hence they are also known as Polymers. The petrochemical industry supplies the monomers for plastics production and manufacturers a wide range of additives to modify their behavior. The size and structure of the polymer molecule determine the properties of the plastic material. In their basic form, plastics are produced as powders of granules. The application of heat and pressure to these raw materials produces the final plastic product for specific end use application. Plastics owe their name to their ability to be shaped to form articles of practical value by various conversion and forming processes. There are some peculiar properties of plastics materials, which make the unique so that products can literally be tailor-made out of these materials. Only 4% of the fuels consumed go to make the plastics; the rest 96% being used for other human needs like transport and heating. It is this small portion of the resource, which helps in contributing towards social and economicdevelopment on the one hand, and protection and conservation of environment on the other hand as we shall see ahead. In fact, plastics have permeated every facet of human life viz, agriculture and water consumption, building construction, telecommunications, small and bulk packaging, education, medicine, transportation, defense, consumer durables to name a few. One of the reasons for great popularity of plastics is due to tremendous range of properties exhibited by them because of their ease of processing. Hence, the demand for plastics has been increasing in modern living.
There are basically three ways by which polymers or plastics can be produced synthetically from simple starting materials. These techniques are referred to as additional polymerization, condensation polymerization and rearrangementpolymerization. During polymerization, the monomer units join together to form a macromolecule. The number of repeating units in a molecule is called as degree of polymerization. A polymer is a macromolecule consisting of several repeating units.
Plastics are classified as thermoplastics or thermosetting resins. Thermoplastic resins, when heated, soften and flow as viscous liquids, when cooled they solidify. The heating and cooling cycle can be repeated many times without much loss of specific properties. This property makes them suitable for recycling. Thermosetting resins liquefy when heated and solidify with continued heating. The polymer undergoes permanent cross-linking and retains its shape during subsequent heating cycles. Thermo set plastics cannot be reheated and remolded; however, thermoplastics can be reprocessed by melting, and hence, readily recycled.
Plastic raw materials are produced by polymerization of small chemical unit called monomer. Thermoplastics (PE, PP, PS, PVC etc.) are generally made by an addition to the polymerization process whereas thermo sets (Nylon, Polyester etc.) are manufactured by condensation of the polymerization process. The thermoplastic or thermo setting resins are further processed by methods known as Blow molding, injection molding. Thermo forming, Rotational molding, Extrusion etc. or a combination of two processes to form various finished end user products.
| PROCESS | PRODUCTS |
| Blow Molding | Jerry cans, Drums, Soft lotion bottles, Custard Powder containers, large automobile components like fenders and bumpers etc. |
| Injection Molding | Buckets, lids, thin walled containers, household items, automobile dashboard components, pens, brushes etc. |
| Thermo Forming | Various disposable throw away items like glasses,party plates and cups etc. |
| Roto Molding | Large dimension articles like water tanks, drums, road barriers etc. |
| Extrusion-Pipes and profile | PVC, HDPE, PPR, pipes, door and window profiles, long length articles etc. |
| Extrusion-Films | Various packaging products like shrink wrap films, multi-layer films, carry bags filament yams, tapes (which are woven into sacks) etc. |
Plastics help in improving life and living around the world. Unique combinations of the properties of plastics have helped mankind in improving life in numerous ways.
PLASTICS IN FOOD CONSERVATION: Packaging is the most visible use of plastics. Previously, packaging was heavy, often fragile and costly. Plastics have revolutionized packaging by providing light, strong, flexible-packaging materials. Plastics packaging reduced overall packaging consumption. In fact, without plastics, overall packaging weight would increase 300 per cent. Packaging applications will certainly grow manifold in the years to come. PET bottles, Olefin moldings and punched have almost changed our life style. PET bottles are extensively used worldwide for packaging of beverages and drinking water. Whether at home or at public places, there is a constant demand for pure drinking water. Bottled water in turn reduces the risk of water borne diseases hence provide an improvement in the health sector.
Plastics packaging also helps preserve food. Wastage in Europe is kept to around two per cent – due in part to plastics packaging – compared to between 20- 50 per cent in the developing world. The traditional materials, jute, paper, sisal, wood, cardboard, tinplate, aluminum and glassware’s were widely replaced with the advent of plastics due to many inherent advantages. Some of them are:
- Plastics Packaging’s are light in weight – 0.2 to 0.3 times of conventional materials.
- Plastics have wide design freedom in the manufacturing of packaging product.
- Plastics provide better aesthetic appeal, color ability, permeability and transparency
- Plastics Packaging Products are non-toxic, non-corrosive, and resistant to chemicals & water.
- Plastics packaging aresterilize able which is an important requirement for packaging in medical field.
- Plastics consume low energy while converting from raw materials into product.
- Plastics protect food, pharmaceuticals and detergents due to good barrier properties.
BIODEGRADABLE PLASTICS: It is generally believed that paper and cellulosic materials are biodegradable and do not pollute the environment like plastics. However, several studies on biodegradable of cellulose material including newspapers have shown that these materials can persist in the environment even after land filling for more than 30 years. Wood, a natural material, which is normally considered biodegradable, may be highly resistance to biodegradation. Sequoia trees are well known to remain stable under normal climatic conditions for 500 years. Trees contains hydroxyl phenols which not only protect the wood from bacterial and fungal attack but are also very powerful antioxidants with activity similar to the most effective synthetic chain breaking antioxidants.
Infact such antioxidants present in polyolefin’s protect them from environmental degradation. In the absence of such protective additive polyolefin’s will easily disintegrate in the environment.
A comparison of overall environmental burden in the process of polyethylene and paper is shown in the table below.
Comparison of air and water pollution associated with plastic and Kraft papers
It is obvious that the energy cost of plastic per pound is substantially less than that of all major competitors.
The conclusion is “The replacement of polyethylene by paper carry bags makes no sense ecologically. The production of polyethylene carry bags requires less energy; and in the process result in less burden to the environment. There is no significant difference in the disposal of polyethylene and paper bags”
CONCLUSION: If we take a comprehensive view of the present and potential benefits of plastics in its multitudinal forms, the implications of furthering the usage of plastics are phenomenal. The last century has seen plastics and its products emerging steadily to becoming a part and parcel of man’s day to day life. Apparels, automobiles, consumer goods, defense & aircrafts and packaging applications, among other, have revolutionized our daily life style.
With further research, better technologies and more resources of our disposal, the plastic industry has greater promises for our future. It intends to change the way we grow our crops, the way we build our roads, the way we manage our country’s defense system and the way we save our natural resources. It has exponential growth opportunities on how we manage our economy – the way we create greater wealth, generate jobs and the way we live our life.
The concerns about the impact of waste and disposal are a small proportion of the larger picture. No doubt these concerns are important but the awareness is there and with a will to mitigate them, there can be no looking back. With this done, there is no disputing the facts that our future generations will inherit a healthier and happier earth by the use of plastics the bottom line being: REDUCE WASTE, REUSE, RECYCLE, and RECOVER.
– WithContributions from Industrial Training Institute, Aundh Pune And Central Institute of Plastics Engineering & Technology (CIPET) India