Category Chemistry

Plastics are derived from natural resources — oil, coal and natural gas. We are using oil so fast that the Earth’s supplies may run out within 100 years. If they do, so will plastics. Scientists are investigating new ideas for making plastics by processing plants such as the sweet potato, bamboo and flax. .61 Using organic raw materials to make plastics would be kinder to the environment. Items such as a car would be easier to dispose of. If a car was made of organic raw materials most of the parts would naturally rot. Instead of scrapping it, you may just end up eating it!

Wildlife

Plastics can be extremely hazardous to wildlife. Each year, many birds become entangled in plastic drinks can holders. Once the plastic is wrapped around a bird’s neck or feet, it is difficult to escape. This causes panic and, ultimately, death.

Pollution

 The Trabant emerged in the 19505 as one of the first cars to be made almost entirely out of plastic. While its benefits included value for money and a vehicle that would not easily rust, it also had its downfalls. The plastic used on this car would not breakdown naturally in the environment and so disposal was difficult. Unfortunately, the Trabant added to the mass waste in landfill sites.

Re-using

Large water containers like these can be re-used many times. This is far more considerate to the environment than disposing of numerous smaller bottles each time you have a drink. it’s also a good idea to donate old computers, compact discs, video tapes, toys and household goods to charity shops for re-use.

Alternative sources

Plastics are made from natural resources that are not renewable. These resources are rapidly running out. Alternative sources such as soya beans and sugars can be processed into plastic products, saving our valuable non-renewable sources.

Picture Credit : Google

Plastics are used to make synthetic fabrics for clothes, curtains, sheets and carpets. Nylon, polyester and acrylic are all plastic fabrics. They are made from thermoplastics. You may wonder why it is necessary to make synthetic fabrics when there are natural ones, like cotton and wool. The answer is that natural fabrics from raw materials are expensive and in short supply.

Clothes made from synthetic fabrics have other advantages such as they do not crease much. However, they are not so comfortable to wear, or as warm, as natural fabrics. Synthetic fabrics are often mixed with natural ones to combine the advantages of both.

A Synthetic Fibre is a chain of small units of chemical substance joined together. Many such single units combine to form single unit called Polymer. Polymer means made of many units joined together.

 Types of Synthetic Fibre

       Rayon– Rayon is synthesized from wood pulp. Rayon resembles silk, so it is also known as artificial silk. Rayon can be dyed in different colours and is much cheaper than silk.

       Nylon– Nylon was first commercially synthesized fibre. Nylon is synthesized from coal, water and air. Nylon is very strong and its fabric is like silk.

       Polyester– Polyester, one of the most popular man-made fibres. It is made of repeating unit of a chemical called ester. It is widely used to make clothes.

       Acrylic– Acrylic is a man-made fibre. Acrylic is known as artificial wool or synthetic wool because it resembles wool. Acrylic is cheaper than natural wool and can be dyed in various colours. This makes acrylic is very popular among other fabrics.

Characteristics of Synthetic Fibres

       Synthetic fibres are cheaper than natural fibre.

       Synthetic fibres are stronger than natural fibre.

       Synthetic fibres are more durable than natural fibre.

       Synthetic fabrics are dried up in less time.

       Synthetic fibres are easy to maintain and wash.

Foamed plastic, synthetic resin converted into a sponge like mass with a closed-cell or open-cell structure, either of which may be flexible or rigid, used for a variety of products including cushioning materials, air filters, furniture, toys, thermal insulation, sponges, plastic boats, panels for buildings, and even lightweight beams. Under appropriate conditions almost any thermosetting or thermoplastic resin can be converted into foam. Plastics that are commonly foamed include vinyls, polystyrene, polyethylene, phenolics, silicones, cellulose acetate, and urethanes.

Foams with a closed-cell structure are produced by incorporating a blowing agent that decomposes at the fusion point of the plastic, releasing gas bubbles that are trapped during the gelling. Foams with an open-cell structure are produced by incorporating an inert gas into the resin under pressure and then releasing the mixture to the atmosphere and curing the resulting foam.

Bubbles and air can be put into plastics to turn them into foams and lightweight plastics. Sometimes the bubbles are big enough to see. In other cases they are microscopic. Plastic foams have a number of uses. They are excellent materials for making packaging like cartons for foods and delicate items which need protecting from knocks.

Rigid foam is mainly used as a heat insulator. It is injected into the spaces between the outer walls of houses to keep them warmer. Some plastic foam can be toxic due to the chemicals involved in making them. Now, many foams are made which are less toxic.

Did you know that paints and adhesives contain plastics? Paints are often made of three different chemicals. A ‘pigment’ provides the colour; a plastic holds the pigment in place and gives a shiny finish; and a ‘solvent’, usually white spirit, makes the paint runny and easy to use. When the paint dries, the solvent evaporates and only the pigment and plastic are left.

Pigments

The pigment is the color chemical in paint. It looks a certain color because it reflects some wavelengths of light and absorbs others. Traditionally, metal compounds (salts) are used to create different colors so, for example, titanium dioxide (bright white chemical often found in sand) is used to make white paint, iron oxide makes yellow, red, brown, or orange paint and chromium oxide makes paint that’s green. Black comes from particles of carbon (think what your burned toast looks like and you’re getting close to a color chemical known as “carbon black”). Different pigments are mixed together to make paint of any color you can imagine.

Binders

Pigments are typically solids, so you couldn’t use them to paint by themselves. They’d be difficult to apply, they wouldn’t spread evenly, they wouldn’t stick to paper or a wall, and they’d wash straight off if they got wet. That’s why paints also contain substances called binders. Their job is to glue the pigment particles to one another, but also to make them stick to the surface you’re painting. Some binders are made from natural oils such as linseed oil, but most are now made from synthetic plastics. Visualize the binder as an invisible skin of plastic with a colorful pigment dispersed through it and you can see just how paint gives a layer of protection.

Solvents

Mix a pigment and a binder and you get a thick gloopy substance that’s difficult to spread. Ever tried painting a wall with treacle? That’s what using a pigment and a binder is like. It’s the reason why paints have a third major chemical component called the solvent. As its name suggests, a solvent is something that dissolves something else. The solvent’s job is to make the pigment and binder into a thinner and less viscous (more easily flowing) liquid that will spread evenly (that’s why paint solvents are sometimes called thinners). Once the paint has spread out, the solvent evaporates into the air, leaving the paint evenly applied and dry beneath it. When you apply a really nasty paint and there’s a smell lingering for days while it dries, that’s the solvent evaporating into the air.

Strong glues like ‘superglue’ are made of thermosetting plastics called epoxy resins. They can stick metal, glass, china, and wood— in fact almost anything!

Laminates and perspex are both hard. Different plastics are needed to make flexible sheets. Carrier bags, light raincoats, shower curtains and food packaging are just some of the products made from plastic sheets.

Food and other articles are often ‘shrink wrapped’. The article is wrapped and sealed in a thin plastic film that has been heated, stretched and then cooled. Although the film stays stretched when it cools, if the wrapped article is passed through a hot tunnel, the plastic melts and shrinks back to its original size, wrapping the item very tightly.

Most Plastic bags are made from polyethylene – more commonly known as polythene, which is made from crude oil and natural gas, non-renewable resources.

The most common way to produce polythene bags is by blown film extrusion, also called the “tubular film process.”

In Blown film production process – polythene melt is extruded through an annular slit die, usually vertically, to form a thin walled tube. Air is introduced via a hole in the centre of the die to blow up the tube like a balloon into the tube causing it to expand and form a bubble. Mounted on top of the die, a high-speed air ring blows onto the hot film to cool it. The tube of film then continues upwards, continually cooling, until it passes through nip rolls where the tube is flattened to create what is known as a ‘ lay-flat’ tube of film. This lay-flat or collapsed tube is then taken back down the extrusion ‘ tower’ via more rollers. The lay-flat film is then either kept as such or the edges of the lay-flat are slit off to produce two flat film sheets and wound up onto reels. If kept as lay-flat, the tube of film is made into bags by sealing across the width of film and cutting or perforating to make each bag. This is done either in line with the blown film process or at a later stage.