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Describe the polymer moulding process shown in the diagram below using the following guidelines: (i) Name the moulding process and describe the principle of operation; (ii) Identify one component produced - Leaving Cert Engineering - Question 6 - 2007
Question 6
Describe the polymer moulding process shown in the diagram below using the following guidelines: (i) Name the moulding process and describe the principle of operatio... show full transcript
Worked Solution & Example Answer:Describe the polymer moulding process shown in the diagram below using the following guidelines: (i) Name the moulding process and describe the principle of operation; (ii) Identify one component produced - Leaving Cert Engineering - Question 6 - 2007
Step 1
Name the moulding process and describe the principle of operation
Answer
The moulding process is known as Compression Moulding. This method is specifically used for thermosetting plastics. In this process, a specific shape is formed using a hollow mould. The polymer is heated and placed in the mould where it is subjected to heat and pressure, leading to its formation in the desired shape. The closing of the mould triggers a chemical reaction known as cross-linking, which solidifies the polymer as it cools down. Once formed, the mould is opened, and the newly shaped object can be extracted. This process requires minimal removal of excess material, commonly referred to as 'flash'.
Step 2
Step 3
State clearly the function of any two of the following additives: Pigments; Plasticisers; Lubricants
Answer
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Pigments: The primary role of pigments is to provide color to the polymer materials. They enhance the aesthetic appeal and can influence other properties like light absorption.
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Plasticisers: These additives are crucial as they improve the flexibility of the polymer. They function by altering the intermolecular forces, thereby allowing the polymer chains to move more freely and reduce brittleness.
Step 4
Explain any three of the following in relation to polymers: Condensation polymerisation; Extrusion; Elastomers
Answer
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Condensation Polymerisation: This process involves the joining of two or more monomers, resulting in the release of a smaller molecule, often water. The monomers connected by this method usually results in a polymer that is chemically stable and can form strong links, making it resistant to heat and solvent.
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Extrusion: This method is used to produce continuous lengths of materials, such as pipes or sheets. In this process, raw polymer granules are fed into a heated barrel and forced through a die using a rotating screw. As the material exits the die, it can be shaped and cooled into the final product.
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Elastomers: These are a type of polymer characterized by their elastic properties. They can stretch significantly while maintaining their original shape due to their coiled structure which contains minimal cross-linking. This allows elastomers to withstand larger forces without permanent deformation.