Rubber processing: the operation used to convert rubber into thin sheets or to apply a uniform rubber coating onto fabric is known as what?
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AExtrusion
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BMastication
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CCalendering
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DVulcanisation
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ECompression moulding
Answer
Correct Answer: Calendering
Explanation
Introduction / Context:Rubber goods manufacturing uses several distinct unit operations. When the goal is to form controlled-thickness sheets or apply rubber films to textiles (e.g., tire cord fabrics, conveyor belts), the process of choice is calendering. Discriminating calendering from extrusion, mastication, and vulcanisation is a core skill in polymer processing.
Given Data / Assumptions:
- Objective: create thin, uniform sheets or coat fabric with rubber.
- Equipment: sets of heavy, polished rolls with adjustable gaps.
- Material: compounded rubber mixes at elevated but non-curing temperatures.
Concept / Approach:Calendering squeezes and stretches rubber stock between counter-rotating rolls, controlling gauge and surface finish while embedding fabric when desired. Extrusion forces rubber through a die to produce profiles or tubing; mastication is mechanical working to soften/shorten polymer chains for processability; vulcanisation is the curing step that creates cross-links, improving elastic recovery, strength, and heat resistance but not used to set sheet thickness or apply coatings by itself.
Step-by-Step Solution:
Match target (thin sheet or coated fabric) with process capabilities.Recognise roll-gap control and fabric feed of calenders.Rule out extrusion (profiled shapes), mastication (pre-mixing softening), vulcanisation (curing chemistry).Select “Calendering.”Verification / Alternative check:Process layouts for tire manufacturing show calender lines preparing skim-coated cord fabrics and innerliner sheets prior to building and vulcanisation.
Why Other Options Are Wrong:
- Extrusion: produces continuous profiles, not textile coatings.
- Mastication: conditioning step, not a forming/coating method.
- Vulcanisation: curing, not sheet/fabric gauge formation.
- Compression moulding: discrete part shaping, not continuous sheet/fabric coating.
Common Pitfalls:Confusing the order of operations: calender to make sheets/coat, then assemble, then vulcanise to final properties.
Final Answer:Calendering