This set of Polymer Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Acrylic Plastics and Fibres”.
1. What is the correct structure of monomer of poly methyl methacrylate?
Explanation: The structure of methyl methacrylate is given by- CH2═C(CH3)−CO−O−CH3
It is the monomer of the polymer polymethyl methacrylate (PMMA).
2. Which of the following mechanism is used in the formation of commercially used polymethyl methacrylate?
a) anionic mechanism
b) cationic mechanism
c) free radical mechanism
d) cannot be said
Explanation: Methyl Methacrylate when polymerized by free radical initiated bulk or suspension polymerization, using peroxide or azonitrile initiators at about 100 ᵒC, gives polymethyl methacrylate as the final product.
3. What is the glass transition temperature of the polymer polymethyl methacrylate?
a) 74ᵒ C
b) 105ᵒ C
c) 93ᵒ C
d) 80ᵒ C
Explanation: PMMA has a glass transition temperature of about 105 ᵒC and a service temperature of about 93 ᵒC. It has heat deflection temperature in the range of 74 to 100 ᵒC.
4. What is the specialized application of PMMA, keeping in mind its excellent optical clarity and high atmospheric resistance?
a) hard contact lenses
c) decoration of appliances
d) insulation wires
Explanation: The combination of excellent optical clarity and outstanding weathering behavior makes PMMA especially useful for hard contact lenses. It is good for the applications that require light transmission and outdoor exposure.
5. For the production of sheets, rods, etc. by bulk polymerization of methylmethacrylate, the complete polymer syrup of high viscosity is poured into the casting cell, just to minimize reaction exotherm and shrinkage. State true or false.
Explanation: For the production of sheets, rods, etc. by bulk polymerization of methylmethacrylate, the monomer methylmethacrylate, firstly is partially polymerized and then the prepolymer syrup of convenient viscosity is poured into the casting cell. This is done to minimize reaction exotherm and obtain sheets free of sink marks and voids.
6. How does the solubility of polyacrylates in oils and hydrocarbons vary with the length of side group attached?
c) remains same
d) increases then decreases
Explanation: The solubitlity of polyacrylates in oils and hydrocarbon increases with the increase in size of the side group attached. The polymer also gets harder and tougher with the decreases in the size of group.
7. Which of the following polyacrylate is used in paints and adhesives formulation?
a) poly (butyl acrylate)
b) poly (methyl acrylate)
c) poly (2-ethylhexyl acrylate)
d) poly (ethyl acrylate)
Explanation: Poly(2-ethylhexyl acrylate) is having a large size ester group which makes it quite softer and so it is used in painting and adhesion formulation.
8. Which of the following monomer can copolymerize with acrylonitrile to improve the dyeability of the acrylic fibre?
a) vinyl acetate
b) methacrylic acid
c) vinyl pyrrolidone
d) all of the mentioned
Explanation: To improve dyeability, feel and texture of acrylic fibre, the polymer is prepared by copolymerizing with 5-15% of monomers like vinyl pyrrolidone, vinyl acetate and methacrylic acid with acrylonitrile.
9. Which of the following properties are not true about polyacrylonitrile?
a) monomer solubility
b) yellowing on heating
c) soluble in dimethyl formamide
d) suffers discoloration on heating
Explanation: Acrylonitrile is a non-solvent for its own polymer and hence, it undergoes heterogeneous polymerization using redox catalyst. On heating, it easily suffers discoloration and starts yellowing and the later turns black. It is soluble in solvents like dimethyl formamide, dimethyl sulphoxide, etc.
10. How is the polymer formed by polymerization of acrylonitrile obtained in the form of?
a) homogeneous solution
Explanation: Acrylonitrile undergoes heterogeneous aqueous polymerization in the presence of redox catalyst and the polymer is obtained in the form of precipitate.
Sanfoundry Global Education & Learning Series – Polymer Engineering.
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