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PRESENTED BY, K S GOURI
B.Ed. PHYSICAL SCIENCE REGISTER NUMBER: 18220384006 SVMCTE, VENDAR.
STANDARD : 8 BASIC SCIENCE
CONTENT FIBRES AND PLASTCS
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Polymer Fibre Rubber Plastic i. Thermoplastic ii. Thermosetting Plastic Plastic And Microns Recycling Symbols Energy From Plastics Let Us Assess Extended Activities References
FIBRES AND PLASTICS
We live in an era of tremendous progress in the field of science and technology. We see a variety of substance around us that are available for improving our life style. A close examination will reveal that most of them are contributions of chemistry. Chemistry has paved way for amazing changes through the maximum utilization of natural resources and also by producing a variety of modern materials. As you know, cotton, silk, wool, jute etc., are the substances used for producing clothing since ancient days. All of them along with other familiar substances like fiber, rubber etc., are made of molecules belongs to a group called polymer. PAGE / 1
1. POLYMER: Polymers are macro molecules formed by the combination of large number of simple molecules (monomers). 1.1 Classifiation oF polymers on the basis of their origin: 1. Natural Polymer Natural polymers occur in nature and can be extracted. They are often water-based. Examples of naturally occurring polymers are silk, wool, DNA, cellulose and proteins etc. 2. Artificial Polymer Synthetic polymers are human-made polymers, often derived from petroleum oil. Examples of synthetic polymers include nylon, polyethylene, polyester, Teflon etc. 1.2 Classification of natural polymers on the basis of their physical properties: 1. Fiber 2. Plastics 3. Rubber
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2.FIBRE: Fibres are the polymers suitable for the manufacture of strong threads. Fibres are classified by their chemical origin, falling into two groups or families: natural fibers and manufactured fibers. Manufactured fibers are also referred to as man made or synthetic fibers. 1. Natural Fibre:
Natural fibre, any hairlike raw material directly obtainable from an animal, vegetable, or mineral source and convertible into nonwoven fabrics such as felt or paper or, after spinning into yarns, into woven cloth. 2. Synthetic Fibre:
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Synthetic fibres are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants (like cotton) or fur from animals Some examples of synthetic fibres are rayon, nylon, polyester, etc 3.RUBBER:
Rubber is an elasticity polymer.Rubber is a natural polymer with elastic properties. Rubber is isolated from the latex obtained from rubber tree. Rubber is a polymer formed by the combination of the monomer molecules isoprene.
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Synthetic Rubber: Synthetic polymer with properties of rubber have been developed this are called Synthetic rubber. Example: NEOPRENE, THIOKOL, BUNA-S, BUNA-N etc. Vulcanization Of Rubber:
Vulcanization is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140– 160°C. The process involves the formation of cross-links between long rubber molecules so as to achieve improved elasticity, resilience, tensile strength, viscosity, hardness and weather resistance. Vulcanization of rubber is the process of converting natural rubber to more strong and elastic form. Natural rubber is mixed with 3 to 5% sulphur and heated at 100 to 150oC to form cross linking of cis−1,4−polyisopropene chains through disulphide bonds.
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4. PLASTIC: A BRIEF HISTOY OF PLASTICS
ALEXANDER PARKES In 1862, Alexander Parkes introduced the world’s first man-made plastic — Parkesine — at the Great International Exhibition in London. It was marketed as a substitute for horns and ivory. Parkes discovered this when he was trying to find a substitute to shellac for waterproofing. Though the product was not a commercial success, Parkesine represented an important first step in the development of man-made plastic. However, the material didn’t start to truly show its potential value and diversity of applications until John Wesley Hyatt, in Albany, New York, discovered a way to manufacture an improved version of Parkesine, most commonly known as celluloid.
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Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be molded, extruded or pressed into solid objects of various shapes. The Basics On 7 Common Types of Plastic: 1) Polyethylene Terephthalate (PET or PETE) 2) High-Density Polyethylene (HDPE) 3) Polyvinyl Chloride (PVC or Vinyl) 4) Low-Density Polyethylene (LDPE) 5) Polypropylene (PP) 6) Polystyrene (PS or Styrofoam) 7) Other. Properties Of Plastic: 1. Light Weight, Strong, Corrosion Free 2. It is a bad conductor of heat 3. It is a bad conductor of electricity 4. Inert/ not reactive with air, water and chemicals. ACTIVITY: ❑ Are plastics with the same property used for all purpose? ❑ Have you seen plumbers using PVC pipes by heating and cooling? ❑ What is the peculiarity of these plastics? ❑ Can we use PVC for making the handles of pressure cooker and iron box? ❑ Observe the changes by heating a piece of PVC and old switches PAGE / 7
For more details visit on the link given below: https://youtu.be/xhRYV_Ky5qQ
The two key categories of plastic are 1.Thermoplastics 2.Thermosetting plastics (thermosets)
Thermoplastic: The plastic that gets softened on heating and hardened on cooling is thermoplastics. This process can be repeated any number of times. Thermoplastics undergo physical change on heating. Different types of thermoplastics are: 1.PET (polyethylene terephthalate) Light, rigid or semi-rigid, naturally transparent or colorless, PET is an excellent moisture and gas barrier and is resistant to impacts. It is one of the most easily recyclable plastics and is used to produce bottles, bags and synthetic fibers for clothing. 2.HDPE (high-density polyethylene) and LDPE (lowdensity polyethylene) Polyethylene is the most common plastic material. Transparent or white, it has excellent insulating properties and is very strong, versatile and cheap. HDPE is translucent, strong and easy to process, resistant to impacts and non-toxic. It is used to make bottles, tanks, bins and containers for transport.
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LDPE can be translucent or transparent. Suitable for contact with food, it is the lightest and most heat-sensitive plastic. It is used for packaging, bags, sacks, cable coatings, containers, pipes and toys. 3.PVC (polyvinyl chloride) PVC is a very versatile plastic, resistant to wear and tear, chemical and atmospheric agents and fire. It is used in the paper industry and for packaging, food containers, credit cards, furnishings, clothing and toys. 4.PP (polypropylene) Transparent, light and strong, this material can be used as both a plastic and a fiber. Easily colored, it does not absorb water. It is used to make textile fibers, couplings, containers for transport, furniture, carpets, ropes and food containers.
5.PS (polystyrene or styrofoam) One of the most important thermoplastic materials, it is transparent, hard and inflammable, very bright and inert against many corrosive agents. It can be given shiny or opaque colors. Polystyrene is commonly used to replace glass, aluminum and wood because it is cheaper. It can also be used in packaging materials (including for foods), containers, boxes, lamps, disposable objects, cups and toys.
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Thermosetting Plastic: The plastic which remains soft when heated during its manufacture, and gets hardened permanently on cooling is thermosetting plastics. Once hardened, they cannot be remolded by heating. Thermosetting plastics on heating undergo chemical change along with physical change. Different types of thermosetting polymer: 1.Bakelite
Bakelite was the first thermoset plastic that was synthesized from synthetic components. The chemical name of Bakelite is ‘Polyoxybenzyl Methylene Glycol Anhydride,’ and its chemical formula is (C6{C}_{6}C6H6{H}_{6}H6O.CH2{H}_{2}H2O)n.
2. Duroplast
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Duroplast is a composite thermoset material that is similar to Bakelite except for the fact that it is reinforced with cotton or wool fibers. One of the most significant properties of Duroplast is that it is lightweight and strong. Due to this property, Duroplast is used in making car bodies, which reduces the cost of using steel for making various car parts. 3. Urea-formaldehyde Resins
Urea-Formaldehyde is also known as Amino plastic or carbamide-methanol. These Thermosets are highly crosslinked and have a semi-crystalline structure. They become rigid very rapidly if the temperature is elevated. They are used as an adhesive for particleboard, laminating decorative items, coating, air filtration, and fiberglass mats. 4.Melamine-formaldehyde Resins
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They are synthesized by reacting Melamine with Formaldehyde under low alkaline conditions. Melamine resins are fire-retardant that is why they are used as additives in the manufacturing of papers, paints, plastics, and flame-resistant textiles. Many other products that are manufactured using these resins are particleboards, laminates, kitchenware, and floor tiles.
5. POLLUTION DUE TO PLASTICS:
Plastic, once considered as a wonderful substance, has now become dreaded substance to be avoided everywhere. Restriction on the production and use of plastics has been enforced world-wide. In our country the use of plastics has been banned in a number of places. You also may be aware that steps have been taken to make hospitals, campuses, zoos and public places plastic free. This is because plastics do not undergo biodegradation like other substances.
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❑ What are the situation in which plastic materials become harmful? 1. Leads to environmental pollution when discarded carelessly 2. Burning of plastics cause air pollution 3. Dumping of plastics in water bodies created water pollution 4. As it does not undergo degradation it will unbalanced the ecosystem Asses the uses of plastic as well as the issues raised by them. Let’s also conduct a debate on the topic ‘Plastics – a boon or a curse ‘. Is plastics the real culprit or the human beings who use it illogically? What measures can be proposed to reduce pollution due to plastics? 1. Avoid disposable plastics products. 2. During functions, use glass/ ceramic/ steel/ utensils or natural substances 3. Use paper, cloth and plant materials, instead of plastics for decorations ❑ Let us practice the 4 R’s to reduce the use of plastics to the maximum extent as well as to avoid the pollution caused by plastics.
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What are the 4 R’s? Reduce- Plastics Reuse- Plastics Refuse-Plastics Recycle-Plastics 6. PLASTIC AND MICRON:
The thickness of plastics is expressed in micron unit.1 micron = 10-6metre (0.000001m). Since plastics with less than 40 micron thickness is easily breakable and may be discarded, its use is restricted in many places.
7. RECYCLING SYMBOLS:
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For effective plastic recycling, it is necessary to identify the type of a particular plastic. Different plastics have been given certain recycling symbols. Triangular arrows with number from 1 to 7 printed on them are used as symbols. 8. ENERGY FROM PLASTICS:
It's possible to convert all plastics directly into useful forms of energy and chemicals for industry, using a process called “cold plasma pyrolysis”. Pyrolysis is a method of heating, which decomposes organic materials at temperatures between 400℃ and 650℃, in an environment with limited oxygen.
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SIGNIFICANT LEARNING OUTCOMES After studying this section, learner can, • Identify polymers and explain their molecular structure. • Identify the characteristics and uses of different plastics and choose them as and when required. • Distinguish between thermoplastic and thermosetting plastics. • Explain the merits and demerits of plastics and use them judiciously in daily life. • Identify the causes and effects of pollution due to plastics and involve in awareness activities.
LET US ASSESS 1.Polymers are macromolecules formed by the combination of many monomers. o How are polymers classified? o Classify the following. Wool, rayon, terylene, cotton. 2.You know what thermoplastics and thermosetting plastics are. o Which of these plastics cannot be recycled o You might noticed that those who collect old plastics do not accept certain type of plastic articles. What are they? What may be the reason for this? PAGE / 16
3.Natural fibres and synthetic fibres are used in the field of textile manufacturing. o Compare their merits and demerits and tabulate. o Which of these clothes is most suited for the following situation? i. While cooking in the kitchen. ii. To wear during summer.
EXTENDED ACTIVITIES 1. Many articles made of plastics can be made using glass, ceramics, steel etc. and by some natural materials like plantain leaf, spathe etc. thereby educing the use of plastics. Identify the possibilities for this and conduct an exhibition in your school. 2. A variety of articles made of plastics are used daily in your house for different purposes. ❑ What are the different purposes? What are the different articles? Prepare a note. ❑ How are these disposed after use? Is this don in the correct way? ❑ Try to find out the amount of plastic abandoned after use at home in one month.
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REFERENCES
❑ https://www.toppr.com/ask/question/what-isvulcanization-of-rubber/ ❑ https://www.britannica.com/topic/natural-fiber ❑ https://www.dentispet.it/plastic-materials/main-types-ofthermoplastics/?lang=en ❑ https://www.hsslive.guru/kerala-syllabus-8th-standardbasic-science-solutions-chapter-17/
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