Tag: plastic
Questions Related to plastic
We come to a conclusion, that plastics are bad conductors of electricity from the following.
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Refrigerators and freezers have a plastic foam core
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Electrical wires have a plastic covering
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Cooking pans have plastic handles
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We use to prepare parachutes
Most of the commonly used household electronics like freezers, washing machine, etc are made of plastic since it is the bad conductor of electricity.
Which of the following is/are reasons of using plastics?
1.They are transparent.
2. They are cheap.
3. They can be moulded into diffrent shapes.
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(1) only
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(2) only
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(1) and (3) only
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(2) and (3) only
Fibre obtained by chemical treatment of wood pulp is called:
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natural Silk
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rayon
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nylon
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polyster
Which is NOT the general characteristics of plastics?
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Good electrical insulators
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Acceptable acoustic insulation
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Resistant to corrosion and many chemical factors
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Have a high production cost
The IUPAC name for Teflon is:
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polytrifluoroethane
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polytetrafluoroethane
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polytrifluoroethylene
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polytetrafluoroethylene
Teflon constitutes:
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carbon,flourine & hydrogen
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carbon,chlorine & hydrogen
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carbon & flourine
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carbon & chlorine
Which of the following is thermosetting polymer?
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Nylon
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Sealing wax
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Polysiloxanes
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Both B and C
Thermosetting polymers: These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. These cannot be reused. Some common examples are polysiloxanes, bakelite, urea- formaldehyde resins, etc.
Three-dimensional molecules with cross-links are formed in the case of a:
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thermosetting plastic
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thermoplastic
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both (a) and (b)
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none of the above
Thermosetting plastic consists of chain of the molecules which are cross-linked, with each other when heated. When thermosetting plastics cross-link, the molecules create a permanant, network which is a $3-D$ structure and can be considered one giant molecule. Once cured, thermosetting plastic cn not be remelted, in the same way that cured concrete cannot be reset.
Garden chairs made of plastic strips and plastic articles get faded, worn out and cracked in sunlight, mainly because of:
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Low melting point of plastic
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Ultraviolet rays
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Heat
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The red colour
Garden chairs made of plastic strips and plastic articles get faded, worn out and cracked in sunlight, mainly because of UV rays. All types of UV can cause a photochemical effect within the polymer which can lead to degradation of some sort to the materials. Absorbed UV energy can exits the photon in a plastic, exciting the photons can create free radicals. Those free radicals can cause breaks in the polymer bonds.
Which of the following are not thermosetting polymers ?
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Bakelite
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polystyrene
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PVC
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Melmac
Thermosetting polymers have different properties to thermosoftening polymers. Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily.
Examples are given below:
- Polyester fibreglass systems: sheet molding compounds and bulk molding compounds
- Polyurithane insulating foams, mattresses, coatings, adhesives, car parts, print rollers, shoe soles, flooring, synthetic fibers, etc. Polyurethane polymers are formed by combining two bi- or higher functional monomers/oligomers.
- Vulcanized rubber
- Bakelite, a phenol formaldehyde resin used in electrical insulators and plasticware
- Duroplast, light but strong material, similar to bakelite used for making car parts
Polyvinyl chloride(PVC) and polystyrene are thermoplastic polymer.
Hence, options B and C are correct.