This set of Casting Question Paper focuses on “Extrusion in polymers – 2”.
1. Extrusion is a process that uses an electric system for processing various polymers.
a) True
b) False
View Answer
Explanation: Extrusion is a process used for the processing of various types of thermoplastics and rubbers. The extrusion process is a simple process in which liquid or molten polymer is forced through a shaped die by applying high pressure. The pressure is basically generated by the action of screw rotation against the barrel wall in the extrusion process.
2. Which of the following equipment is used for controlling the temperature of polymer material in the extrusion process?
a) Thermo resister
b) Thermometer
c) Thermocouple
d) Glass tube
View Answer
Explanation: In extrusion process, polymer material pellets are fed into an extruder by a hopper. Then the material is conveyed by a feeding screw and forced through a shaped die that converts polymer materials into continuous polymer products. Heating elements are placed on the barrel which soften and melt the polymer. The temperature of the polymer material is mainly controlled by thermocouples.
3. Thermosetting polymers can be processed by extrusion process by forming cross-linking in the extruder.
a) True
b) False
View Answer
Explanation: Extrusion process is mostly used for thermoplastics polymer materials; it can also be used for processing the elastomers and thermosetting polymers, which basically causes cross-linking in the extruder during the heating process of polymer material. The plastic or polymer products can be further formed by the thermoforming process.
4. In processing polymers, injection moulding process is almost similar to extrusion process except for the screw operation.
a) True
b) False
View Answer
Explanation: Injection moulding process is similar to extrusion process. The only difference between the two processes is in the screw operation. In extrusion, screw rotates continuously which provides output of continuous products like pipe, rod and sheet. A reciprocating screw is used in injection moulding which rotates while moving in forward and backward directions.
5. Extruder is a device used for the finishing of processed polymer products in the extrusion process.
a) True
b) False
View Answer
Explanation: In the extrusion process, extruder is a machine tool or device that forces ductile and soft heated solids through die openings of the desired shape to produce a continuous film, strip, or tubes of polymer materials. In this process, many kinds of polymers like thermoplastics, thermosetting, elastomers etc. are processed with the help of extruder.
6. Continuous type of extruder is generally equipped with rotating parts in the extrusion process.
a) True
b) False
View Answer
Explanation: There are mainly two types of extruder in the extrusion process of polymers, which are continuous and discontinuous extruder. Continuous extruders are generally fitted with rotating components. And in discontinuous extruders, plastic or polymer is extruded in a recurrent manner, which is only suitable for batch type production processes like injection moulding.
7. Multiple screw extruders are mostly preferred than the single screw extruders in the extrusion process.
a) True
b) False
View Answer
Explanation: In the extrusion process, extruders are equipped with a screw as their main mixing part. Screw extruders are mainly of two types which are single and multiple screw extruders. In most of the cases, single screw extruders are used for the processing of polymer materials in the industries, because of its simple design, low cost and high reliability.
8. In the extrusion process, a cast type barrel is mainly used for the heating of polymer material.
a) True
b) False
View Answer
Explanation: There are mainly two types of barrel heaters used in the extrusion process, which are band and cast barrel. The band type barrel is used for heating the polymer material while the cast type includes some channels to contain a flow of cooling medium which is usually water, but the oil is more preferred because it can prevent thermal shock to the barrel.
9. Extruder die is a machine part that gives final shape to the polymer material used in the extrusion process.
a) True
b) False
View Answer
Explanation: Extruder die is a machine part that gives final shape to the polymer material in the extrusion process. It produces a channel through which liquid polymer exit the extruder by applying pressure that increases in the barrel during the process. The liquid polymer comes out from the die with a constant speed, that’s why the design of die is very important for specification and accuracy.
10. In the extrusion process, a water cooling system is used which automatically controlled by a sensor.
a) True
b) False
View Answer
Explanation: In the extrusion process, the extruder includes a water cooling system that circulates around the barrel mechanism. The water cooling system is generally controlled by a sensor that automatically controls the system. The sensor also selects the temperature at a predefined point in the processing section of polymer materials.
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