Fig. 1 shows a food container made from a single sheet of polymer material using a manufacturing process. The product is manufactured in large quantities us...

(a) The manufacturing process used to make this food container from a single sheet of polymer is vacuum forming. [1] In vacuum forming, a thermoplastic sheet is clamped in a frame, heated until soft and pliable, then draped over (or into) a mould. A vacuum pump removes the air between the sheet and the mould, causing atmospheric pressure to push the softened sheet tightly against the mould surface, replicating its shape. After cooling, the formed shape is removed and trimmed.

A suitable thermoplastic for this container is HIPS (high-impact polystyrene). [1] HIPS is lightweight, food-safe, easy to thermoform, and produces a good surface finish. PET and polypropylene are also acceptable choices for food containers.

(b) The process used to manufacture continuous lengths of polymer pipe is extrusion. [1] In extrusion, polymer granules are fed from a hopper into a heated barrel where an Archimedean screw melts and pushes the material through a shaped die. The continuous profile emerges from the die and is cooled (often by passing through a water bath) to set its shape.

A suitable polymer for a domestic cold water pipe is UPVC (unplasticised polyvinyl chloride). [1] UPVC is rigid, lightweight, resistant to corrosion and chemicals, and does not contaminate drinking water, making it ideal for plumbing applications. [1]

(c) The thermosetting polymer commonly used for the decorative laminated surface labelled A (a kitchen worktop) is melamine formaldehyde. [1]

Two properties that make melamine formaldehyde suitable for a kitchen worktop surface:

1. It is heat resistant, so hot pans or dishes placed on the worktop will not damage or mark the surface. [1]
2. It is scratch resistant and hard-wearing, meaning the surface withstands daily use including chopping, cleaning, and general wear without deteriorating. [1] It also has good resistance to staining from food and household chemicals.

(d) The manufacturing process shown in Fig. 4 is blow moulding. [1] A suitable polymer for making drinks bottles using this process is PET (polyethylene terephthalate). [1]

Two stages of blow moulding:

1. A heated tube of molten polymer called a parison is extruded and clamped inside a two-part mould. [1]
2. Compressed air is blown into the parison, inflating it outward against the inner walls of the mould to take on the bottle shape. The polymer cools against the mould surface, and the mould opens to release the finished bottle. [1]

(e) The material labelled A is acrylic (PMMA / polymethyl methacrylate). [1]

At the heated zone, the acrylic sheet softens and becomes pliable along the narrow line of heat. [1] The localised heating makes only the strip directly above the heater element flexible, while the rest of the sheet remains rigid. This allows the sheet to be bent along the heated line to a precise angle.

Acrylic can be reshaped using this process because it is a thermoplastic: when heated, the weak intermolecular bonds between its polymer chains break, allowing the chains to move and the material to flex. [1] On cooling, the bonds re-form and the material holds its new shape.

One product that could be made using line bending is a point-of-sale display stand or a photo frame. [1]

(f) A suitable polymer for Product P (safety helmet) is ABS (acrylonitrile butadiene styrene). [1] ABS is tough and impact resistant, which is essential for a safety helmet that must protect the wearer's head from falling objects or collisions. [1]

Product Q (electrical socket) is made from a thermosetting polymer rather than a thermoplastic because a thermosetting polymer will not soften or deform when exposed to heat generated by electrical current flowing through the socket. [1] A thermoplastic could melt or warp near a heat source, creating a fire hazard. The thermoset also provides excellent electrical insulation.

The polymer commonly used for Product R (washing-up bowl) is polypropylene. [1] It is lightweight, flexible, and resistant to hot water and detergents, making it suitable for everyday kitchen use. [1]

(g) The part labelled A in Fig. 7 is the hopper. [1] The hopper holds the raw polymer granules and feeds them by gravity into the heated barrel of the injection moulding machine.

The heated barrel melts the polymer granules as they pass through, converting them from solid pellets to a molten state. [1] The Archimedean screw rotates to push and force the molten polymer forward along the barrel and then injects it under high pressure into the mould cavity. [1]

Two advantages of injection moulding for manufacturing polymer products in large quantities:

1. It offers a high production rate with fast cycle times, making it economical for mass production. [1]
2. It produces very consistent and identical products with high accuracy and excellent surface finish, reducing waste and quality-control costs. [1]

(h) Selecting the most suitable polymer for products X, Y and Z:

• Product X (shampoo bottle): HDPE, because it has good chemical resistance so it will not react with the shampoo, and it is tough and stiff enough to hold its shape. [2]
• Product Y (garden planter): Polypropylene, because it is lightweight and has good fatigue resistance, so the planter can withstand repeated outdoor use. [2]
• Product Z (plug casing): Urea formaldehyde, because it is a good electrical insulator and is heat resistant, making it safe for an electrical plug. [2]

A thermoplastic can be repeatedly heated and reshaped; a thermosetting polymer undergoes a permanent chemical change when set and cannot be reshaped. [1]

When disposing of thermoplastic products, they can be recycled by melting and re-moulding, which reduces waste sent to landfill and conserves raw materials. However, if not recycled, thermoplastics are not biodegradable and persist in the environment for hundreds of years. [1]