QCAA Engineering Materials

Nylon is a non-biodegradable polymer; while used in sutures, it would require a second surgery to remove if used as a screw, making it less suitable than bioabsorbable options.

Polypropylene is a non-absorbable material typically used for surgical meshes and sutures, not for temporary fixation devices that should dissolve over time.

Polyvinyl chloride (PVC) is generally used for external medical devices like tubing and blood bags, not implants, due to biocompatibility issues and the presence of plasticizers.

Low-carbon steel typically contains less than $0.3\%$ carbon (often $0.05\%$ to $0.25\%$), which is below the range specified for torsion bars.

High-carbon steel generally contains between $0.6\%$ and $1.4\%$ carbon, making it harder and more brittle than the material described.

Mild steel is a common term for low-carbon steel (approximately $0.05\%$ to $0.25\%$ carbon), which does not match the $0.3\%$ to $0.5\%$ range.

While polyethylene is used for wash bottles and storage containers, it has a lower melting point than polypropylene and cannot typically be autoclaved, making it less common for general-purpose beakers.

Polylactic acid (PLA) is a biodegradable plastic with low heat resistance, making it unsuitable for laboratory environments where heating and chemical stability are required.

Polyvinyl chloride (PVC) is commonly used for tubing but is rarely used for beakers due to issues with chemical leaching and lower thermal stability compared to polypropylene.

While often used interchangeably with low carbon steel, the term "mild steel" typically refers to the range of $0.15\%$ to $0.30\%$ carbon. Steel with $0.11\%$ carbon is often specifically called "dead mild steel," making the broader category of "low carbon steel" the most accurate choice.

Medium carbon steel contains a higher carbon content, typically ranging from $0.30\%$ to $0.60\%$, which provides a balance of ductility and strength not found in the lower $0.11\%$ composition.

High carbon steel contains carbon ranging from $0.60\%$ to $1.50\%$. A carbon content of $0.11\%$ is far too low to be classified in this category.

Nylon is primarily used for textiles and engineering components like gears; it is generally too expensive and absorbs moisture, making it unsuitable for drainage pipes.

While polypropylene is used in some piping applications, it is less common than PVC for general waste water drainage due to differences in rigidity and cost.

Polylactic acid (PLA) is a biodegradable polymer used for packaging and medical devices; it lacks the long-term durability and stability required for infrastructure piping.

Polyvinyl chloride (PVC) has relatively high dielectric losses and is primarily used for low-voltage applications (like household wiring) rather than high-voltage transmission.

While polypropylene has good electrical properties, it is generally less flexible and more brittle at low temperatures than polyethylene, making it less suitable for standard cable insulation.

Polystyrene is a rigid and brittle plastic, making it mechanically unsuitable for use as flexible cable insulation despite its good dielectric properties.

Boiler plates require high ductility and weldability to withstand pressure and fabrication, so they are typically made from low carbon (mild) steel rather than brittle high carbon steel.

Railway tracks are generally made from medium to high carbon manganese steel to balance toughness and wear resistance, whereas plain high carbon steel is primarily reserved for tools.

Engine crankshafts require good toughness and fatigue strength to handle dynamic loads, so they are usually manufactured from medium carbon steel or alloy steel.