One characteristic of thermosets is that ___________. View NCERT Solutions for all chapters of Class 8, FREE Downloadable NCERT Solutions.Works without internet. (c) nylon (b) Blended fabrics contain only synthetic fibres. (a) they become soft on cooling (b) polyester and wool. Three properties of synthetic fabrics are as follows: (a) The odd one is teflon. Give two examples of thermosetting plastics. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students. (e) Terylene, a synthetic fibre, can be used instead of wool. (c) they can be repeatedly remoulded into desired shapes Which of the following is a polyester fibre? Sand (silicon dioxide (SiO2), sodium carbonate (Na2CO3) and calcium carbonate (CaCO3) are the three raw materials needed to make glass. They become soft only the first time; they become hard. As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. (a) The odd one is teflon. As the containers used for microwave cooking should be able to sustain reheating without causing any damage to the food kept in them, these containers can be made of thermosetting plastics. 3. They are produced by the combination of. We provide a total manufacturing solution that covers planning, molding, decorating and processing. Recycling of plastics is very costly. (a) sand, sodium bicarbonate, limestone It is a monomer (small molecule) unit, while polyester, cotton and nylon are polymers (larger molecules made up of smaller monomer units). Name the following: These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. Phenol Formaldehyde Resin Powder Heat Resistance for Brake Pads Product description . Anu bought a sweater which was not very expensive. (b) Thermoplastics become soft on heating. Thus, the sweater was not pure wool, but it was made of synthetic acrylic fibre. Students can Download Chapter 15 Polymers Notes, Plus Two Chemistry Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations. (b) they become hard after heating For example, polythene and PVC are thermoplastics. The list of materials mentioned above can be classified as This is the key to their strength, toughness and durability. (c) man-made materials and plastics. Thermoplastic polymers These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. (e) polyester, cotton, ester, nylon. polymer, blended fibre. Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics. It is a polymer (synthetic fibre) made up of small chemical molecules called esters. Melamine and Bakelite are thermosetting plastics. (e) False source:www.intercosmo.net ; Thermoplastics: The plastic which becomes soft on heating and can be remolded into desired shape is called thermoplastic. (a) synthetic fibres and plastics for example : Bakellite , melanin, Formaldehyde Thermoplastic Plastic are kind of plastic which can be moulded again and again by heating and easily reused.For example :PVS, Polysterine , nylon , polythine Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. They are not infected by bacteria or fungus and are resistant to insects. Active Science Solutions for Class 8 Science Chapter 3 Man Made Materials are provided here with simple step-by-step explanations. Which of the two is a thermosetting plastic: PVC or bakelite? It is used to make floor tiles, kitchenware and fire resistant fabrics. Such plastics are called thermosetting plastic. The correct statement should be: Bakelite® molding compounds are engineering thermosets (ETS) not engineering thermoplastics (ETP). Example: Bakelite, melamine, etc. Bakelite & Melamine Injection Molding Machine, Model: LCH-H80 toLCH-H500 ; LCH-V100 to LCH-V850, There are two types of injection features: the thermoplastic type and thermosetting plastic type. They absorb water and do not catch fire easily. Henry Ford made his own deadly version of Bakelite by mixing phenol, formaldehyde and defatted soybean meal which reacted to create a thermoplastic resin that could be molded under pressure to create durable nonstructural plastic parts, such as radio knobs, light switch pulls, distributor caps, body trim, etc. Bakelite is a very poor conductor of heat and electricity and it is used for making electrical switches. (b) acrylic Is it thermoplastic or thermosetting plastic ? Plastic is a very generalized term for polymers that can mean either a thermosetting or a thermoplastic Plastic. (d) Polyester fibres are obtained from petroleum products. It is used to make electrical switches and handles of utensils. The formation process of these two types of plastics also differs. Like bakelite and Perspex, the objects made of melamine can have polished and shiny surfaces which can be achieved by molding or treating objects with very fine abrasives. Differentiate between thermoplastics and thermosetting plastics. Rayon looks like silk. They cannot be moulded more than once as they take a firm shape once they are heated and cooled. (a) Annealing is the process by which glass is cooled and made tougher. These fibres have mixed properties of both the fibres involved in its production. The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. (d) All the statements are correct. giving reasons. Making electric fittings such as electric switches, Making plugs and sockets. Explanation: (c) polythene They can be moulded into different shapes again and again. At home, when she burnt a small piece of fibre from the sweater, it smelled like burning plastic. The word polymer is coined from two Greek words poly means many and mer means unit. As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. (a) dacron (c) dacron, acrylic, terene, terylene 40) State two uses of melamine ? (a) Melamine (b) Polythene (c) PVC (d) Nylon. Usually, the material is thermoplastic type if the product material is plastic; the material is thermosetting type if the product is Bakelite and melamine. They are produced by the combination of synthetic fibres and natural fibres. Soln: Answer is (b) Rayon. (d) polyester. (b) gas given off when PVC is burnt The correct statement should be: (d) True (f) False It is used to make floor tiles, kitchenware and fire resistant fabrics. Plastics are not biodegradable and take thousands of years to degenerate. Synthetic condensation polymers have a wide array of household, industrial, commercial, and medical uses … (d) PVC. (e) Blended fabrics are made by the combination of natural and synthetic fibres. This results in environmental pollution. (c) they do not conduct heat or electricity (b) The odd one is polycot. Soln: Answer is (a) Melamine. The overuse of plastics leads to many problems like environmental pollution, health hazards, etc. (d) acrylic. (d) cotton, jute, silk, rayon It is a blended fabric, but rayon, nylon and acrylic are not. In the growing consumer market of the 1930s and after, Bakelite faced competition from other thermosetting resins such as urea formaldehyde and melamine formaldehyde and from new thermoplastic resins such as cellulose acetate, polyvinyl chloride, polymethyl methacrylate, and polystyrene. polythene, polystyrene, nylon, PVC, rayon, terene, acrylic, formica, polycot, melamine (e) The odd one is ester. Define the following: As wood contains huge amount of cellulose, rayon (synthetic fibre) is prepared chemically from wood pulp (cellulose). (b) silicon, sodium bicarbonate, limestone (a) Thermosetting plastics remain hard on reheating and can sustain high temperatures. Blended fabrics contain both synthetic and natural fibres. Rewrite the false ones correctly. Fuji Bakelite is a plastics manufacturer that offers a balance of technology and art. 39) Write two uses of Bakelite ? (d) they become soft again and again on reheating. (d) polyester and cotton (d) The odd one is rayon. What is the sweater most likely made of? Therefore, thermoplastics are not used for making saucepan handles. (b) polyester fibres and objects made of glass. 2. 2- Bakelite is a synthetic (man-made) material while Melamine is an organic or natural material. (b) Thermoplastics are not used for making saucepan handles. Bakelite, or polyoxybenzylmethyleneglycolanhydride, is an early plastic. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. Plastic - Thermoplastic and thermosetting plastic | Bakelite | Melamine. (c) they do not conduct heat or electricity. Types of Polymerisation 1. Recycling of Plastic. (a) False (b) they can be moulded into any shape Acrylic is a synthetic fibre, which is light, soft and warm. (b) Hydrogen chloride gas is given off when PVC is burnt. The correct statement should be: Bakelite is a thermosetting plastic, it cannot be molded again whereas Melamine, being a thermoplastic, can be molded any number of times adn reshaped. Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. Which of the following statements is true for rayon? 1. Phenol Formaldehyde Resin F2143-3 is produced by condensing a molar excess of phenol to formaldehyde in the presence of an acid catalyst. Polyesters are wrinkle-free and do not require ironing. (c) large molecules made by joining many small molecules together Once processed and cured, they are infusible and cannot be re-melted or dissolved. Plastics are bad conductors of heat and electricity (good insulators). Thermoplastic type material can be recycled and reusable, while the runner or material waste for thermosetting plastic type cannot. (c) they do not conduct heat or electricity We can sort the given fabrics into natural, synthetic and blended fibres as shown in the table below: Find the odd one out in the following. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. Chain Growth Polymerisation or Addition Polymerisation It involves formation of reactive intermediate such as free radical, a carbocation or a carbanion. Which of the following correctly lists the raw materials needed to make glass? (f) Polyester fibres like dacron and terene are made from petroleum products. Even if they catch fire, they do not stick to the body of the person who is holding it. (f) two fabrics made from petroleum products. Bakelite and melamine are examples of thermosetting plastic. It resembles wool but does not shrink or wrinkle. (a) Annealing is the process by which glass is cooled and made tougher. They absorb very less water. Acrylic is a synthetic fibre that can be used instead of wool. Students are advised to practice the NCERT MCQ Questions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics with Answers Pdf free download is available here. Dusters made of cotton (natural fibre) are good for use in kitchen. 1 Answer +1 vote . (a) polyester and nylon. (c) The odd one is acrylic. Explanation: Thermosetting plastics when moulded once can not be softened by heating. 3- Bakelite is a synthetic plastic and Melamine is … We have provided Synthetic Fibres and Plastics Class 8 Science MCQs Questions with Answers to help students understand the concept very well. (b) It is obtained from wood containing large amount of cellulose. Melamine is a thermoseting plastic which is resistant to fire and can tolerate heat better than other plastics. Check the below NCERT MCQ Questions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics with Answers Pdf free download. Melamine is a thermosetting plastic. It is used in electric switches, plugs, handles of pressure cooker and tea kettle, radio and TV cabinets, etc Bakelite, Melamine, etc are some examples of it. Nylon, rayon, acrylic, terene and polycot are synthetic fibres. (a) the process by which glass is cooled and made tougher Polythene, polystyrene, PVC, melamine and formica are plastics. 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