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With reference to the polymer manufacturing process shown in the diagrams below, answer the following: (i) Name the process and describe the principle of operation - Leaving Cert Engineering - Question 6 - 2012
Question 6
With reference to the polymer manufacturing process shown in the diagrams below, answer the following: (i) Name the process and describe the principle of operation.... show full transcript
Worked Solution & Example Answer:With reference to the polymer manufacturing process shown in the diagrams below, answer the following: (i) Name the process and describe the principle of operation - Leaving Cert Engineering - Question 6 - 2012
Step 1
Name the process and describe the principle of operation.
Answer
The process is known as Compression Moulding. This technique is suitable for thermosetting plastics. It uses a split mould formed into the shape of the desired object. The principle of operation involves combining heat and pressure to mold the material into the desired form. Initially, the polymer is introduced in a powder or slug form into the mould cavity. Once the mould is closed, heat causes the material to soften. The pressure then shapes the material to fit the mould. After curing through an applied heat source, the mould is opened and the finished product is extracted.
Step 2
Step 3
Step 4
Distinguish between thermoplastics and thermoset plastics using each of the following headings:
Answer
(i) Polymerisation process:
- Thermoplastics: These undergo addition polymerization.
- Thermoset plastics: These undergo condensation polymerization.
(ii) Chemical bonding:
- Thermoplastics: The chemical bonding consists of secondary bonding with weak van der Waals forces.
- Thermoset plastics: They have strong covalent bonds due to cross-linking that occurs during the curing process.
(iii) Internal structure:
- Thermoplastics: Typically have a linear or branched structure.
- Thermoset plastics: Exhibit a cross-linked structure, which contributes to their rigidity.
(iv) Properties:
- Thermoplastics: Characterized by a low melting point, thus allowing for easy moulding and recycling.
- Thermoset plastics: Features include a high melting point and high tensile strength, making them suitable for high-temperature applications.
Step 5
Explain in detail any three of the following:
Answer
(i) Elastomer:
Elastomers are polymers that possess elastic properties, allowing them to stretch significantly and return to their original shape. They consist of linear chains entangled and subjected to minimal cross-linking. This gives elastomers their unique flexibility, making them ideal for products like rubber bands and certain types of seals.
(ii) Catalyst:
Catalysts are substances that accelerate chemical reactions without being consumed in the process. They can lower the energy barrier required for a reaction, facilitating processes like polymerization by initiating or speeding up the reaction rate. Catalysts are essential in various industrial applications to increase efficiency.
(iii) Blow moulding:
Blow moulding is a manufacturing process utilized for creating hollow objects, such as bottles. In this process, a parison (a preform tube) is placed in a mould. Air is then introduced into the parison, which inflates and takes the shape of the mould. The mould closes around the parison to shape it into the final product. This is an efficient method for producing lightweight plastic containers.