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Bicycle helmets are manufactured from a range of thermoplastic polymers - Leaving Cert Engineering - Question 7 - 2022
Question 7
Bicycle helmets are manufactured from a range of thermoplastic polymers. The shell is generally manufactured from polyethylene terephthalate (PET) and the inner from... show full transcript
Worked Solution & Example Answer:Bicycle helmets are manufactured from a range of thermoplastic polymers - Leaving Cert Engineering - Question 7 - 2022
Step 1
Describe, with the aid of a diagram, a suitable thermoplastic manufacturing process for the polyethylene terephthalate (PET) shell.
Answer
The suitable thermoplastic manufacturing process for PE (polyethylene terephthalate) shell is Vacuum Forming.
- Clamp Setup: A plastic sheet is secured in a frame.
- Heating: Heat is applied to the sheet until it becomes pliable.
- Forming: The mould is lifted into the softened sheet.
- Creating a Seal: A vacuum is applied, pulling the sheet onto the mould.
- Cooling: Once shaped, the plastic cools and solidifies.
- Removal: The excess material is trimmed away to finalize the shell.
This method is effective for creating complex shapes typical in bicycle helmet shells.
Step 2
Give two properties of expanded polystyrene (EPS) which make it suitable for use in the helmet liner.
Answer
- Dissipates Shock: EPS is effective in absorbing impact energy, protecting the wearer during a collision.
- Thermal Insulation: EPS has low thermal conductivity, providing insulation and comfort for the user.
Step 3
Select a suitable polymer for the manufacture of the chin straps on the bicycle helmet. Justify your selection.
Answer
A suitable polymer for chin straps is Nylon.
- Strength: Nylon is known for its high tensile strength, ensuring durability in use.
- Flexibility: It can be manufactured into woven and flexible straps, allowing for comfort and adjustability in fitting.
Step 4
Outline the function of a catalyst in the addition polymerisation process.
Answer
A catalyst is used to accelerate or slow down the chemical reaction in polymerisation. It is introduced to enhance the reaction rate, allowing monomers to join together more efficiently, ultimately facilitating the formation of polymers.
Step 5
Explain, with an example, the term copolymerisation.
Answer
Copolyerisation is the process where two or more different monomers are combined to create a copolymer. An example of this is Styrene-acrylonitrile (SAN), which combines styrene and acrylonitrile to achieve improved properties over either monomer alone.
Step 6
Step 7
Outline two environmental benefits of promoting widespread recycling of mobile phone covers.
Answer
- Reduces Pollution: Recycling minimizes waste, decreasing pollution across ecosystems.
- Conserves Resources: By reusing materials, recycling helps to conserve natural resources and reduces the need for raw material extraction.
Step 8
Describe, with the aid of a diagram(s), the main differences between linear and cross-linked chains in polymers.
Answer
Linear polymers consist of long, unbranched chains where the monomers form a simple continuous structure, usually associated with thermoplastics.
Conversely, cross-linked polymers feature interconnected chains through covalent bonds, creating a three-dimensional network. This structure imparts greater strength and thermal stability.
Diagram: (Include visual representation here showing linear chains beside cross-linked structures.)
Step 9
Compare glass and polycarbonate as suitable materials in the production of mobile phone screen protectors, making reference to: - impact resistance - transparency - hardness.
Answer
- Impact Resistance: Polycarbonate has excellent impact resistance, making it less prone to shattering compared to glass.
- Transparency: Both materials offer high transparency, but polycarbonate is more prone to scratching.
- Hardness: Glass is generally harder and offers better resistance against scratches than polycarbonate.
Step 10
Describe the process of polymer lamination.
Answer
Polymer lamination involves the bonding of thin layers of materials using resin and heat. The process typically includes:
- Layer Alignment: Different plastic layers or sheets are aligned to the desired configuration.
- Heat Application: Heat is applied to melt the resin, promoting adhesion between layers.
- Pressure Application: Pressure consolidates the layers, ensuring an even bond.
- Cooling: The laminated structure is cooled to solidify and finalize the bond.