Thermoplastic is a type of a polymer which can be easily melted by providing heat in order to recycle the material. MCQ Questions for Class 8 Science with Answers were prepared based on the latest exam pattern. It is not a polyester synthetic fibre, while dacron, terene and terylene are polyester synthetic fibres that are manufactured from petroleum products. It is a synthetic fibre, while cotton, jute and silk are natural fibres. Which of the following statements is true for rayon? Thermosetting plastics become soft only the first time; when they are reheated, they become hard (take firm shape). Thermoplastic type material can be recycled and reusable, while the runner or material waste for thermosetting plastic type cannot. Choose the thermoplastic and thermosetting plastic from the following: Melamine, PVC, polythene, nylon, Bakelite. (c) they do not conduct heat or electricity. 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 Phenol Formaldehyde Resin Powder Heat Resistance for Brake Pads Product description . For example, cotton is a naturally occurring polymer that is made up of glucose as monomer units. (d) substances that are easy to mould and can regain their shape (a) Thermosetting plastics remain hard on reheating and can sustain high temperatures. Sand (silicon dioxide (SiO2), sodium carbonate (Na2CO3) and calcium carbonate (CaCO3) are the three raw materials needed to make glass. Thermoset are useful in high temperature applications since they do not soften like a thermoplastic. Differentiate between thermoplastics and thermosetting plastics. hermosetting plastics remain hard even at high temperatures. (c) they do not conduct heat or electricity As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. They can be moulded into different shapes again and again. Anu bought a sweater which was not very expensive. Thermoplastic: Plastics that can be deformed easily upon heating and can be bent easily. All questions and answers from the Active Science Book of Class 8 Science Chapter 3 are provided here for you for free. Recycling of plastics is very costly. (c) It is a naturally occurring fibre obtained from wood. (c) polythene Blended fabrics contain both synthetic and natural fibres. Melamine and Bakelite are thermosetting plastics. Bakelite and melamine are examples of thermosetting plastic. (a) False (e) False Bakelite is a thermosetting plastic, it cannot be molded again whereas Melamine, being a thermoplastic, can be molded any number of times adn reshaped. Rayon looks like silk. A thermoset material as the name implies can be heated only once because an irreversible reaction occurs so that the material remains solid in what ever form it is in when the reaction takes place. Is it thermoplastic or thermosetting plastic ? These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. It is because of these advantages of polyester over cotton that polyester is blended with cotton to form polycot. (c) polyester and acrylic. It is a blended fabric, but rayon, nylon and acrylic are not. The correct statement should be: Bakelite is a very poor conductor of heat and electricity and it is used for making electrical switches. (b) The odd one is polycot. (b) Thermoplastics become soft on heating. It is a blended fabric, but rayon, nylon and acrylic are not. Such plastics are called thermosetting plastic. Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. It is a polymer (synthetic fibre) made up of small chemical molecules called esters. giving reasons. Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. Thus, the sweater was not pure wool, but it was made of synthetic acrylic fibre. (a) Annealing is the process by which glass is cooled and made tougher. (b) gas given off when PVC is burnt (b) rayon, nylon, polycot, acrylic (a) Annealing is the process by which glass is cooled and made tougher. (b) teflon Soln: Answer is (a) Melamine. What is the sweater most likely made of? (e) polyester, cotton, ester, nylon. Which of the following correctly lists the raw materials needed to make glass? Thermosetting Plastic: Some plastics do not get deformed on heating, and cannot be re-molded into a new shape. Define the following: (b) acrylic At home, when she burnt a small piece of fibre from the sweater, it smelled like burning plastic. 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