All About Plastics

                                                

A. HISTORY OF PLASTICS

Plastic comes from the Greek Word “plastikos” which means capable of being shaped or molded. This term was used even before plastic was invented, right from 1600’s.

First natural plastics are -

Tortoise shell                         Shellac (Insect Secretion)                         Tree Resins

                                           

Earlier days combs were made out of tortoise shells. Shellac is a resin secreted by female lac bug.  According to the Mahabharata, an entire palace was built out of dried shellac.

Plastic Invention – Time lines

Invention of Cellulose Nitrate -1840 - In the 1840s German chemist Christian Schönbein accidentally developed cellulose nitrate when he spilled mixture of  nitric acid, and sulfuric acid on his cotton apron . Cellulose is found in the cells of plants. Cellulose nitrate is a highly flammable dough like substance primarily used in the manufacture of explosives. Cellulose nitrate's properties as a molding substance interested other scientists of the time.

First man made (semi-synthetic) plastic -1862- British inventor Alexander Parkes  experimented with using a variety of solutions to dissolve cellulose nitrate, after which the material could be precipitated in one or another form. At first he called the reformulated cellulose nitrate "synthetic ivory," because of its similarity to natural ivory, but later referred to the product as parkesine, named after himself. This is the first man made plastic.

From this material, Parkes manufactured a number of buttons, pens and combs.

 

 

In 1862 he displayed this material officially at the Great International Exhibit in London. Parkes made small commercial gains with Parkesine and eventually sold the rights to Daniel Spill, who subsequently began production of the substance around 1865. But the cost of materials needed was very high.

Substitute for ivory made billiard balls- 1871- At around the same time in the United States, a billiard ball company advertised a $10,000 reward for the discovery of an alternate material to ivory. An American inventor, John Wesley Hyatt  and his brother developed a mixture of cellulose nitrate and camphor that was an even more satisfactory substitute for ivory than was Parke's parkesine. The Hyatts obtained a patent for their new product, to which they gave the name celluloid. In 1871 Hyatt and his brother Isaiah formed the American Celluloid Company, which is today the Plastics Division of the Celanese Corporation. However, the highly inflammable nature of celluloid was always a hazard to its manufacture and use, and as newer plastics materials became available its use gradually declined.

First Synthetic plastic- Bakelite- 1907 -Dr. Leo Baekeland engineered the first totally synthetic plastic in 1907. Compared to other plastics available at the time, such as celluloid, Baekeland’s thermosetting phenolic was more stable. Once molded, this new material would not burn or soften when reheated, or dissolve. Bakelite was an instant commercial success. It was electrically resistant, chemically stable, heat resistant, rigid, moisture and weather resistant. It was very widely used for its electrical insulating capability. Baekeland sold the rights to his invention to the Eastman Kodak Company that first used it for camera bodies. J.W. Hyatt, inventor of celluloid and founder of the Hyatt-Burroughs Billiard Ball Company, personally ordered his company to stop using celluloid and substitute Bakelite for their billiard balls due to its superior performance.

By the 1940s, many other polymers were introduced to the world, and these included acrylic, PVC, polyethylene, Teflon, nylon and others. In the following decade, plastic began to be used in numerous products, ranging from packaging to new textiles, and it also paved the way for the invention of innovative products such as televisions and computers.

B. TYPES OF PLASTICS AND THEIR USES

Plastics can be broadly classified into 3 types.

1. Elastomers ( Rubber like material)- The elastomers although elastic can not be reshaped by heating, hence they are heat resistant. They are usually used in the making of automobile tires.

Polyurethanes: Mattress, cushion, insulation, toys

Silicones:     Surgical gloves, oxygen masks in medical applications

2. Thermosetting plastics - Thermosetting plastics just like the elastomers once set after cooling cannot be reformed again and are extremely heat resistant. They are hard and durable.Thermosetting plastics when heated, will chemically decompose, so they can not be recycled. Yet, once a thermoset is cured it tends to be stronger than a thermoplastic Typically used in automobile parts and construction materials.

Unsaturated Polyesters: lacquers, varnishes, boat hulls, furniture

Epoxies and Resins:        Glues, coating of electrical circuits, fiberglass in helicopter blades, boats

3. Thermoplastics - Thermoplastics are recyclable and constitute 80% of the plastics used in the world. Thermoplastipolymers melt when heated and return to their original state when cooled again. Thermoplastics can be remelted and remolded. For example, a plastic bottle that contained a soft drink could be reformed into the fibres of a fleece jacket.

C. How plastics are made now ?

Though earlier plastics were made from plant parts like cellulose , now a days most synthetic plastics come from crude oil but coal and natural gas is also used.
When crude oil is refined gasses are given off. The gasses are broken down into Monomers. These are chemical substances consisting of a single molecule. Thousands of these are linked together in a process called Polymerization to form new compounds called Polymers. By the application of heat and pressure to the plastic granules, we can get the required shape. Several processes like injection molding, extrusion, compression molding, transfer molding etc. are used to make the plastic products.

D. Plastic – Is it a boon or bane?

Plastic is a boon

because plastics are everywhere! From our pillows and mattresses (cellular polyurethane or polyester) to cars and hi-tech computers, plastics are there.

1. Plastic has replaced metals and glass as the primary material used.

2. Plastics are poor conductors of heat and electricity. Hence they provide good insulation for the wiring and are durable in extreme weather conditions.

3. Since plastic is able to withstand heat, they are widely used in space shuttles.

4. They are light weight and colorful.
5. Safe for children when they are food grade plastics. Ordinary plastics cause health hazards to humans when eaten in them.
6. Handy as disposable bags, carry bags, wrapping paper, etc.

7. They are non-reactive and hence used as water pipes. Plastic bottles can be used to store juices.

8. In fact, plastic has helped in advancements in satellites, shuttles, aircraft, and missiles. As a result, civilian air travel has improved, as well as military air power and space exploration.

Bane because

1.   Non biodegradable. Plastics pollute beaches and oceans. Plastic bags litter the landscape.

2.  Plastic bags litter the landscape.

3. Obstruct underground water percolation.
4. Microbes cannot destroy them.
5. Produce harmful gases when burnt.
6. Plastic bags thrown into the open drains and sewers clog them and cause stagnation of water, which in turn poses health hazards
7. Disposable syringes, drip bottles, blood and urine bags and other medical accessories when disposed off in an irresponsible manner, cause a lot of serious health problems.
8. Animals sometimes feed on plastics and die painfully as plastic chokes their digestive and respiratory tracts.

E. Measures to reduce plastic pollution

Since it is obvious that plastic cannot be routed out completely,we must at least try and reduce our dependency on it.

3 ways to minimize the bad effects of plastic on envirionment  is  the ’3R’ policy –

 Reduce, Reuse and Recycle.

Reduce

1. Avoid accepting plastic bags when you finish shopping. Instead, carry a paper or a jute bag with you when you go shopping.

2. Avoid using plastic chairs or tables, you could use wood/metal instead.

3.  Plastic is made from crude oil. So less usage of plastic also means less demand for crude oil products.

Reuse

1.    More than 90 percent of consumers reuse their plastic grocery bags at home for purposes ranging from waste basket liners to lunch bags to pet clean up

Recycle

1.   Do not dispose plastic which can be recycled. That’s another means to reduce production of more plastic. The plastic that undergoes the recycling process results in a lower quality product. Hence, such plastic has reduced application range in today’s world. Our aim should be to increase the domain of usage of such lower quality plastic and ensure that we have an equal demand for recycled plastic as much as we have for good quality plastic

The more hazardous variant of plastic, the non-recyclable poses a greater threat to our environment.

A few steps that could be taken to tackle this problem are

1.    Governments should ban production of non-recyclable plastic and also the manufacture of products that use them.

2.    Non-recyclable plastic can be used for asphalting roads, as supplementary building materials, and as supportive structures.

3.   Extensive research must take place in finding better methods of disposing non-recyclable plastic.

4.   People must be educated about the benefits of recycling and must be taught to avoid the usage of non-recyclable plastic.

5.   Avoid disposing of plastic along with organic wastes. Do not throw waste foodin plastic bags or containers. You might just save a life.

6.    As common people, the least we could do before buying a plastic article is tolook at the label to find out if it is recyclable.

7.    Avoid disposing of plastic along with organic wastes. Do not throw waste food in plastic bags or containers. You might just save a life.