How are the materials used in product design classified, and what is the difference between each category?
The classification of materials used in product design: papers and boards, natural and manufactured timbers, ferrous and non-ferrous metals and alloys, thermoplastic and thermosetting polymers, and composites, with the defining features of each category.
A focused answer to OCR A-Level Product Design on the classification of materials: ferrous, non-ferrous metals and alloys, thermoplastic and thermosetting polymers, hardwoods, softwoods and manufactured boards, papers and boards, and composites, with the defining feature and a named example of each category.
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What this dot point is asking
OCR wants you to classify the materials used in product design into their main families, state the defining feature of each, and back it with a named example. The five families you must know are papers and boards, timbers (natural and manufactured), metals (ferrous, non-ferrous and alloys), polymers (thermoplastic and thermosetting) and composites.
Papers and boards
Papers and boards matter in Product Design for packaging, modelling and graphic products, and they are highly recyclable, which links to the sustainability content.
Timbers: natural and manufactured
Natural timber is anisotropic (its properties vary with the grain direction) and can warp with moisture; manufactured boards are more dimensionally stable and come in large, uniform sheets, which is why flat-pack furniture uses MDF and chipboard.
Metals: ferrous, non-ferrous and alloys
Alloying is how designers tune a metal: adding chromium to steel gives the corrosion resistance of stainless steel; adding zinc to copper gives the hardness and machinability of brass for taps and fittings.
Polymers: thermoplastic and thermosetting
The single most-tested point is the bonding: thermoplastics rely on weak secondary bonds that heat can overcome; thermosets rely on strong covalent cross-links that heat cannot, which is why only thermoplastics can be re-formed and easily recycled.
Composites
Composites give a high specific strength (strength-to-weight ratio), which is why they replace metals where saving weight is worth the higher cost, but they are hard to recycle because the matrix and reinforcement cannot easily be separated.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksState what is meant by a ferrous metal and a non-ferrous metal, and give one named example of each.Show worked answer →
A Component 01 short-answer recall question. One mark for each definition and one for each correct example.
A ferrous metal is a metal that contains iron as its main element, so it is usually magnetic and will rust (corrode) unless protected; a named example is mild steel (or cast iron, or high carbon steel). A non-ferrous metal contains no iron, so it is generally non-magnetic and more corrosion-resistant; a named example is aluminium (or copper, zinc or tin).
A common dropped mark is naming an alloy such as brass as simply non-ferrous without noting it is an alloy, or naming stainless steel as non-ferrous (it is ferrous, because it is iron-based even though it resists rust).
OCR 20216 marksExplain the difference between a thermoplastic polymer and a thermosetting polymer, referring to their molecular structure, and give one named example and one suitable product for each.Show worked answer →
A Component 01 extended short-answer question marked by points within a levels structure. Markers reward the structural cause linked to the working behaviour.
Award marks for: a thermoplastic has long, tangled polymer chains held together by weak intermolecular (secondary) bonds, so heating overcomes those weak bonds and the material softens and can be reshaped repeatedly (the process is reversible); a named example is acrylic (PMMA) or polypropylene, suited to a product such as a kettle body or a chair shell because it can be injection moulded and recycled. A thermosetting polymer forms strong covalent cross-links between chains when first heated and cured, so it sets permanently and cannot be remelted or reshaped (heating again only chars it); a named example is urea formaldehyde or melamine formaldehyde, suited to an electrical fitting or a pan handle because it stays rigid and heat-resistant in use.
A top answer pins the difference to the bonding (weak intermolecular forces versus permanent covalent cross-links), not just to the observation that one melts and one does not.
Related dot points
- The physical and mechanical properties of materials (strength, hardness, toughness, ductility, malleability, elasticity, plasticity, density, conductivity, durability) and how they govern the suitability of a material for a product.
A focused answer to OCR A-Level Product Design on the physical and mechanical properties of materials: tensile and compressive strength, hardness, toughness, ductility, malleability, elasticity, plasticity, density and conductivity, with definitions, the calculation of density, and how each property governs material choice.
- Smart materials that change a property in response to an external stimulus (shape memory alloys, thermochromic and photochromic pigments, piezoelectric and electroluminescent materials) and modern materials developed by research (Kevlar, graphene, nanomaterials, polymorph), and their use in products.
A focused answer to OCR A-Level Product Design on smart and modern materials: shape memory alloys, thermochromic, photochromic, piezoelectric and electroluminescent materials, and modern materials such as Kevlar, graphene, nanomaterials and polymorph, with the stimulus, the response and a product application for each.
- The selection of materials and standard stock forms (sheet, bar, rod, tube, extrusion, granules, pre-formed sections) for a product, weighing functional, aesthetic, economic, manufacturing, availability and environmental factors.
A focused answer to OCR A-Level Product Design on selecting materials and stock forms: the functional, aesthetic, cost, availability, manufacturing and environmental factors, the standard stock forms (sheet, bar, rod, tube, extrusion, section, granules), and how a designer justifies a material choice for a product.
- Shaping and forming processes for metals (casting, forging, machining), polymers (injection moulding, blow moulding, extrusion, vacuum forming, rotational moulding) and timber (sawing, turning, laminating), and the tooling, accuracy and scale each suits.
A focused answer to OCR A-Level Product Design on shaping and forming processes: casting and forging of metals, machining, injection moulding, blow moulding, extrusion, vacuum forming and rotational moulding of polymers, and timber processes, with the tooling cost, accuracy and scale each suits.
- The sustainability of materials and resources: finite versus renewable resources, sustainable timber (FSC), recycling of polymers and metals, the WEEE directive, and how material choice affects a product's environmental impact.
A focused answer to OCR A-Level Product Design on the sustainability of materials and resources: finite versus renewable resources, sustainable timber and the FSC, the recycling of polymers and metals, the WEEE directive, and how material choice affects environmental impact.
Sources & how we know this
- OCR A Level Design and Technology (H404-H406) specification — OCR (2017)