chapter-3-synthetic fibres and plastics.pptx

educational ppt

1. CLASS VIII General Science Subject Teacher ( Babli Bhardwaj)

2. CHAPTER 3 SYNTHETIC FIBRES AND PLASTICS

3. The synthetic fibres, on the other hand, are made by human beings. That is why these are called synthetic or man-made fibres. A synthetic fibre is also a c h a i n of together. sm a ll Each u n its j o i n e d sm a ll u n it is actually a chemical substance. Many such small units combine to form a large single unit called a polymer . Examples polyethene,polyeaster . INTRODUCTION

4. TYPES OF SYNTHETIC FIBRES RAYON NYLON POLYESTER AND ACRYLIC

5. TYPES OF SYNTHETIC FIBRES Fabric obtained from silk fibre was very costly. But its beautiful texture fascinated everybody. Attempts were made to make silk artificially. Towards the end of the ni n et e en t h c e nt u r y , scientists were successful in obtaining a fibre having properties similar to that of silk. R A YON

6. TYPES OF SYNTHETIC FIBRES Such a fibre was obtained by chemical treatment of wood pulp. This fibre was called RAYON OR ARTIFICIAL SILK . Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fibre. It is cheaper than silk and can be woven like silk fibres. R A YON

7. TYPES OF SYNTHETIC FIBRES It can also be dyed in a wide variety of colours. Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets. R A YON

8. Nylon is another man-made fibre. In 1931, it was made without using any natural raw material (from plant or animal). It was prepared from coal, water and air. It was the first fully synthetic fibre. TYPES OF SYNTHETIC FIBRES NYLON

9. Nylon fibre is strong, elastic and light. It was lustrous and easy to wash. So, it became very popular for making clothes. We use many articles made from to o thbru s h e s, car such a s socks, r o pes, seat sleeping b a gs, cu r t a ins nylon, tents, belts, etc. TYPES OF SYNTHETIC FIBRES NYLON

10. Nylon fibre is strong, elastic and light. It was lustrous and easy to wash. So, it became very popular for making clothes. We use many articles made from to o thbru s h e s, car such a s socks, ro p es, seat slee p ing bags, cur t a i n s nylon, tents, belts, etc. TYPES OF SYNTHETIC FIBRES NYLON - CHARACTERSTICS

11. Nylon is also used for making parachutes and ropes for rock climbing. A nylon thread is actually stronger than a steel wire. TYPES OF SYNTHETIC FIBRES NYLON - USES

12. ACTIVITY - 1 Take an iron stand with a clamp. Take a cotton thread of about 60 cm length. Tie it to the clamp so that it hangs freely from it. At the free end suspand a pan so that weights can be placed in it. Add weights one by one till the thread breaks. Note down the total weight required to break the thread. This weight indicates the strength of the fibre. Repeat the same activity with threads of wool, polyester, silk and nylon. Tabulate the data as shown in Table. Arrange the threads in order of their increasing strength.

13. ACTIVITY - 1 Repeat the same activity with threads of wool, polyester, silk and nylon. Tabulate the data as shown in Table. Arrange the threads in order of their increasing strength. Precaution : Note that all threads should be of the same length and almost of the same thickness. 

14. POLYESTER AND ACRYLIC Polyester is another synthetic fibre. Fabric made from this fibre does not get wrinkled easily. It remains crisp and is easy to wash. So, it is quite suitable for making dress material. You must have seen people wearing nice polyester shirts and other dresses. Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn.

15. POLYESTER AND ACRYLIC PET (polyethylene terephthalate) is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

16. POLYESTER AND ACRYLIC We wear sweaters and use shawls or blankets in the winter. Many of these are actually not made from natural wool, though they appear to resemble wool. These are prepared from another type of synthetic fibre called Acrylic . The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap.

17. POLYESTER AND ACRYLIC They are available in a variety of colours. Synthetic fibres are more durable and a f fordable them more which makes po p ular th a n natural fibres.

18. CHARACTERISTICS OF SYNTHETIC FIBRES Synthetic fibres possess unique characteristics which make them popular dress materials. They dry up quickly, are durable, less expensive, readily available and easy to maintain.

19. ACTIVITY - 2 Take two cloth pieces of the same size, roughly half a metre square each. One of these should be from natural fibre. The other could be a synthetic fibre. You can take help of your parents in selecting these pieces. Soak the pieces in different mugs each containing the same amount of water.

20. OBSERVE AND ANSWER D o s y nt h et i c l e s s /mo r e wat e r th a n f a b ri c s soak the natural fabrics? Do they take less/more time to dry? What does this activity tell you about the characteristics of the synthetic fabrics?

21. ACTIVITY - 3 Take the pieces out of the containers after five minutes and spread them C o m p a r e in the sun for a few the wat e r each minutes. v o l u me o f the remaining in container.

22. PLASTICS Plastic is also a polymer like the synthetic fibre. All plastics do not have the same type of arrangement of units. In some it is linear, whereas in others it is cross-linked. Plastic articles are available in all possible shapes and sizes.

23. PLASTICS The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be re c y c le d, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

24. PLASTICS When we add hot water to a plastic bottle, it gets deformed. Such plastic which gets deformed easily on heating and can be bent easily are k n own as THERMOPLASTICS. Polythene and PVC are some of the examples of thermoplastics.

25. PLASTICS On the other hand, there are some plastics which when moulded once, can not be softened by heating. These are called TH E RMO S E T T I NG PLASTICS . Two examples are bakelite and melamine.

26. BAKELITE BAKELITE is a poor conductor of heat and electricity. It is used for ma k i n g e l e c tr i c a l switches, handles of various utensils . PLASTICS

27. ca n t o l e r a te h e a t b e tt e r than other p l a s tic s . I t is used for making floor tiles, kitchenware and fabrics which resist fire . MELAMINE Mel a mi n e is a v e r s a t ile mat e ri al . It r e s i sts fi r e and PLASTICS

28. PLASTICS AS MATERIALS OF CHOICE Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts, too. The list is endless if we start counting articles like slippers, furniture and decoration pieces, etc.

29. PLASTICS AS MATERIALS OF CHOICE PLASTIC IS NON-REACTIVE Metals like iron get rusted when left exposed to moisture and air. But plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.

30. PLASTICS AS MATERIALS OF CHOICE PLASTIC IS LIGHT, STRONG AND DURABLE Since plastic is very light, strong, durable and can be moulded into different shapes and sizes, it is used for various purposes. Plastics are generally cheaper than metals. They are widely used in industry and for household articles.

31. PLASTICS AS MATERIALS OF CHOICE PLASTICS ARE POOR CONDUCTORS Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic. As mentioned above, handles of frying pans are also made of plastic.

32. PLASTICS AND THE ENVIRONMENT A mat e ri a l decomposed w h i ch through g e ts n a t u r al processes, such as action by b a c t e ri a , is c a l l e d BIODEGRADABLE . A material which is not easily decomposed by natural processes is termed as NON-BIODEGRADABLE .

33. PLASTICS AND THE ENVIRONMENT

34. PLASTICS AND THE ENVIRONMENT Sin c e p l a s tic ta k es s e v e r al y e a r s to d e comp o s e , it i s not en v ir o n m ent fr i en d l y . environmental It causes Bes i d e s, the burning pollution. proces s i n the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.

35. PLASTICS AND THE ENVIRONMENT Avoid the use of plastics as far as possible. Make use of bags made of cotton or jute when you go for shopping. The biodegradable and non biodegradable wastes should be collected separately and disposed off separately. It is better to recycle the plastic waste. Most of the thermoplastics can be recycled. Make a list of items that can be recycled.

36. PLASTICS AND THE ENVIRONMENT As a responsible citizen remember the 4 R principle. REU S E, R E CYCLE RED U CE, AND RECOVER . De v e l op h a b i ts whi c h are environment friendly.

37. PLASTICS AND THE ENVIRONMENT

38. KEYWORDS ACRYLIC ARTIFICIAL SILK NYLON PLASTIC POLYESTER POLYMER POLYTHENE RAYON SYNTHETIC FIBRES TERYLENE THERMOPLASTICS TH E R M OSET T I NG PLASTICS

39. Any Questions Please…

40. Prepared By IT CLUB, Sainik School Amaravathinagar Post: Amaravathinagar Dist: Tiruppur, Tamilnadu Club I/c Praveen M Jigajinni DCSc & Engg,PGDCA,ADCA,MCA,MSc(IT),MTech(IT), M.Phil (Comp Sci) For Any Queries Please feel free to contact: Email Id : Cell No: [email protected] 9431453730

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