Fig. 8 shows three polymer products labelled X, Y and Z. All the bits are smooth. It is made in a shop. The table below lists three polymers and their prope...

(a) Selecting the most suitable polymer for each product using the table of properties:

Product X (shampoo bottle):

• The most suitable polymer is HDPE (high-density polyethylene). [1]
• HDPE has good chemical resistance, so it will not react with or be degraded by the shampoo or other toiletry chemicals inside. It is also tough and stiff, meaning the bottle holds its shape and resists splitting when squeezed. [1]

Product Y (garden planter):

• The most suitable polymer is polypropylene. [1]
• Polypropylene is lightweight, making the planter easy to move around the garden, and it has good fatigue resistance, so the planter can withstand repeated stresses from being moved, filled with soil, and exposed to outdoor temperature changes without cracking. [1]

Product Z (plug casing):

• The most suitable polymer is urea formaldehyde. [1]
• Urea formaldehyde is a good electrical insulator, which is essential for safety in an electrical plug, and it is heat resistant, so the casing will not soften or deform from the heat generated during electrical use. [1]

(b) The difference between thermoplastic and thermosetting polymers relates to their molecular structure and behaviour when heated:

• A thermoplastic can be repeatedly heated and reshaped because it softens when heated. [1] Its polymer chains are held together by weak intermolecular forces that break on heating and re-form on cooling, allowing the material to be recycled and remoulded multiple times.
• A thermosetting polymer undergoes a permanent chemical change (cross-linking) when first heated and moulded. [1] Once set, the strong covalent cross-links between polymer chains cannot be broken by reheating, so the material cannot be reshaped or recycled by melting.

(c) One environmental consideration when disposing of thermoplastic products:

Thermoplastics can be recycled by collecting, sorting, melting, and re-moulding them into new products. [1] This reduces the volume of plastic waste sent to landfill and conserves the crude oil from which the polymers are originally derived, lowering the demand for raw materials and reducing the environmental impact of extraction. [1]

Alternatively, if thermoplastics are sent to landfill rather than recycled, they are not biodegradable and persist in the environment for hundreds of years, occupying landfill space and potentially breaking into microplastics that harm wildlife and ecosystems.