Fig 11 shows a hand-held LED camping lantern designed for outdoor use. The body of the lantern is blow moulded from high-density polyethylene (HDPE). A push...
Question 1 Report
Fig 11 shows a hand-held LED camping lantern designed for outdoor use. The body of the lantern is blow moulded from high-density polyethylene (HDPE). A push-button switch mechanism on the base completes the circuit that powers the LED cluster at the top. The lantern must withstand being dropped from a height of 1.5 metres onto a hard surface without cracking. The fig shows the lantern with the base cap removed, revealing the battery compartment and a small circuit board.
(a) Give one property of HDPE that makes it suitable for the body of an outdoor lantern. [1]
(b) Explain why HDPE is classified as a thermoplastic polymer. [2]
Answer Details
(a) One property of HDPE suitable for the body of an outdoor lantern:
Good impact resistance / toughness [1] - HDPE is a tough, durable polymer that can withstand being dropped from a height of 1.5 metres onto a hard surface without cracking. This is essential for a portable outdoor product that will inevitably experience knocks and drops during camping use. Other valid properties include chemical resistance, weather resistance, lightweight nature, and waterproof characteristics.
(b) Why HDPE is classified as a thermoplastic polymer:
- HDPE softens and becomes mouldable when heated to its melting point (approximately 130 °C), allowing it to be shaped using processes such as blow moulding. [1]
- This is because its polymer chains are held together by weak intermolecular forces (van der Waals forces) rather than permanent covalent cross-links. When heated, these weak forces break and the chains can move relative to each other. On cooling, the forces re-form and the material becomes rigid again. This process is reversible, meaning HDPE can be remelted and reshaped, and is therefore recyclable. [1]
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