Man-made Materials Science Notes
Natural and man-made materials
|Natural materials||Man-made materials|
|Naturally obtained materials that we use for our daily needs are natural materials.||Materials manufactured in the factories after research on the natural materials are called man-made materials.|
|E.g. Wood, rock, minerals, water are natural materials.||E.g. Glass, plastic, artificial threads, thermocol, etc.|
→ Plastic is a man-made material made up of organic polymers.
Properties of Plastic
- Plasticity, (Therefore plastic can be moulded into shape.)
- Not affected by humidity, heat, rain, etc.
- Can take up any colour.
- Bad conductor of heat and electricity.
- Light-weight and easy to carry.
Plastic and environment
→ Degradable materials:
Those materials that can be naturally degraded, are called degradable materials.
→ Non-degradable materials:
→ The materials that do not degrade through natural processes are called non- degradable materials. E.g. Plastic being non-degradable, it is an environmental pollutant.
→ The use of plastic should be reduced as far as possible as it causes environmental pollution. Jute bags, cloth bags, paper bags, etc. can be a better option for the plastic carry bags.
→ However, certain plastic items are almost irreplaceable such as plastic in healthcare sector which is in the form of saline bottles or syringes.
Microwave cookware is plastic. In microwave, metal cookware cannot be used. Teflon used for scratch-resistance, is a kind of plastic. Airplanes need some plastic parts. Lenses and artificial teeth are made up of poly aery lie. There are more than 2000 different types of plastics. But one must be careful in plastic use.
- Reduce – Minimal use
- Reuse – Using the resources again
- Recycle – Using again after processing
- Recover – Obtaining the materials again.
Use of 4R principle is important in reducing the environmental pollution. It also promotes sustainable living.
Thermocol is formed from polystyrene. This complex material is a good shock absorber and an insulating material. Upon heating to more than 100 °C it transforms into liquid state. On cooling, it returns to solid state. This makes it possible to give desired shape to the thermocol.
→ Adverse effects of excessive use of thermocol on environment and human:
→ Disease-causing and carcinogenic effect: Styrene in thermocol has cancer-causing (carcinogenic) substances. Therefore, if anyone is in long term contact with thermocol, there are increased chances of being affected by blood cancer or lymphoma.
→ Non-biodegradable nature: Natural degradation of thermocol does not take place easily. If it is destroyed by burning, poisonous gases are released through it causing toxic air pollution.
→ Excessive use
People tend to use thermocol in mass gatherings. The plates and cups made up of thermocol can affect the health. Reheating food kept in thermocol can be also hazardous as styrene may dissolve in such food. Eating in thermocol cups or plates will thus not only cause environmental problems but also health effe0cts.
→ Occupational hazard to those working in thermocol factory: Long term contact with thermocol may develop the problems of eyes, respiratory system, skin, digestive system, etc. It is also harmful for pregnant women as it may induce abortion. Skin burns are caused by liquid styrene.
- Glass is man-made material which is used on a large scale.
- It was discovered suddenly by Phoenician traders while cooking in desert. They understood that glass can be formed by heating together sand and limestone. This eventually developed the technique of glass production.
- Glass is hard but brittle solid and crystalline material formed from mixture of silica (Si02) and silicate.
- Different types of glasses are dependent upon the proportion of silica and other components in the glass.
- E.g. Sodalime glass, boro-silicate glass, silica glass, alkali-silicate glass, etc.
Production of Glass
- Mixture of sand, soda, lime and small quantity of magnesium oxide is heated in furnace for making the glass.
- Sand, i.e. silicon dioxide melts at 1700 °C. To melt the mixture at low temperature at 850 °C, pieces of discarded glass are added to it.
- After all the ingredients of mixture are liquified, it is heated up to 1500 °C and immediately cooled.
- Sudden cooling makes the mixture homogeneous, amorphous and transparent instead of crystalline.
Properties of Glass
- Glass becomes soft and can be moulded into any shape after heating it up.
- According to the ingredients, the density of glass is determined.
- Slow conductor of heat. But on quick heating of cool glass or on quick cooling of hot glass, it may crackdown.
- Bad conductor of electricity. Thus, used as insulator in electric appliances.
- Transparent, allowing most of light to pass through.
- Oxides of either chromium, vanadium or iron in the glass, makes large amount of light to be absorbed in glass.
→ Types of Glass and Uses:
|Type of glass||Production process||Uses/ Specific features|
|Silica glass||Use of silica in its production. Silica glass show minimum expansion on heating.||Not affected by acid and alkali. Thus, used to produce laboratory glasswares.|
|Borosilicate glass||Melting the mixture of sand, soda, boric acid and aluminium oxide is done for producing borosilicate glass.||The medicine bottles made up of borosilicate glass. There is no effect on medicines if stored in this glass. Pharmaceutical industry uses borosilicate glass for storing medicines.|
|Alkali silicate glass||Production – by heating the mixture of sand and soda.||Glass is soluble in water, it called ‘water glass’.|
|Lead glass||Production – by melting the mixture of sand, soda, limestone and lead oxide.||Very clear or transparent, thus used in manufacturing of light bulbs, tubes, etc.|
|Optical glass||Production – by mixture of sand, soda, limestone, barium oxide and boron.||Forms pure glass. Used in spectacles, lenses, microscopic lenses, etc.|
|Coloured glass||Oxide of specific metal is mixed during manufacturing process of soda lime glass.||Ferrous oxide → bluish green glass Copper oxide → red glass.|
|Processed glass||Processing done on the glass.||Glass with improved quality and utility, E.g. reinforced glass, plain glass, fibre glass, fen glass, translucent glass, etc.|
Effect of glass on environment
Greenhouse gases like sulphur dioxide, nitrogen dioxide, carbon dioxide are released due to burning of fuel at 1500 °C, at the time of glass production.
→ Being non-degradable, the glass pieces remain unchanged in the ecosystem, causing harm to living organisms.