Modification of properties (AQA GCSE Design and Technology): Revision Notes
Modification of properties
Polymers can be enhanced and modified by adding special ingredients called additives. Understanding how these work, along with biodegradable alternatives, is essential for creating polymers with specific properties for different applications.
What are additives?
Additives are special ingredients mixed with polymers to enhance or change their properties. Think of them like ingredients in a recipe - each one serves a specific purpose to make the final product better suited for its intended use.
Types of additives
Stabilisers
Stabilisers help protect polymers from breaking down over time. There are three main types you need to know:
Ultraviolet light stabilizers prevent polymers from becoming discoloured or brittle when exposed to sunlight. Without these, plastic garden furniture would quickly fade and crack in the sun.
UV Protection in Action Bio-stabilizers are added to reduce damage from microorganisms like bacteria and fungi. These are particularly important for polymers used outdoors or in damp conditions.
Heat stabilizers prevent plastics from decomposing when exposed to high temperatures during manufacturing processes. This ensures the polymer maintains its properties during production.
Fibres
Glass fibres are mixed into polymer resin to create incredibly strong, rigid structures. This reinforcement technique is commonly used in car bodies, boat hulls, and other applications requiring high strength-to-weight ratios.
Filler and foamants
Bulk materials are added to polymers to reduce costs while maintaining functionality. Expanded foam products are perfect examples - they use less actual polymer material while still providing the desired properties like insulation or cushioning.
Plasticisers
These additives improve the flow of polymers during moulding processes and make the final product less brittle. Plasticisers essentially make rigid polymers more flexible and easier to work with.
Pigments
Pigments change the colour of polymers from their natural base colour. This allows manufacturers to create products in any desired colour for aesthetic purposes.
Fragrances
Added during the moulding process, fragrances mask unpleasant smells that might come from the base polymer. You might notice this in products like bin bags or cleaning supplies.
Why use additives?
There are several important reasons why additives are essential in polymer production:
- Easier processing: Making polymers flow better during manufacturing
- Improved appearance: Adding colours and masking odours
- Cost reduction: Using cheaper filler materials
- Better mechanical properties: Making products stronger, more durable, and less brittle
- Extended lifespan: Protecting against degradation over time
- Environmental benefits: Reducing environmental impact
Biodegradable polymers
Traditional polymers made from crude oil don't break down easily in the environment. To address this problem, scientists have developed new polymers from plant-based materials that can biodegrade naturally.
These biodegradable polymers break down when exposed to moisture and warmth through bacterial action. While they're non-toxic, they cannot be recycled with conventional oil-based polymers, so they require separate disposal methods.
Examples of biodegradable polymers
Worked Example: Polyactic Acid (PLA)
PLA is easily moulded and commonly used in:
- 3D printing filaments
- Disposable cutlery
- Compost bags
It's one of the most versatile biodegradable options available.
Polycaprolactone (PCL) comes in different forms like Polymorph 62° or Coolmorph 42°. These can be easily moulded and remoulded at low temperatures by hand, making them popular for prototyping and craft applications.
Polyhydroxybutyrate (PHB), also known as Biopol™, can be easily coloured but has low chemical resistance. It's particularly useful for short-term applications like food packaging and shampoo bottles.
Real-world applications
Understanding polymer modification helps explain many everyday products.
Worked Example: Surfboard Construction
Surfboards use multiple additives in their construction:
- Foamants: Create the polymer foam core for buoyancy
- Glass fibres: Mixed with resin to create the hard, durable outer shell
- Stabilizers: Protect against UV damage and water exposure
Similarly, PVC guttering and drainpipes need multiple additives: UV light stabilisers prevent sun damage, bio-stabilizers protect against microorganisms, and heat stabilisers prevent decomposition during the high-temperature manufacturing process.
Key Points to Remember:
- Additives are essential ingredients that modify polymer properties for specific applications
- Six main types of additives each serve different purposes: stabilisers, fibres, fillers/foamants, plasticisers, pigments, and fragrances
- Biodegradable polymers offer environmentally friendly alternatives made from plant materials
- Real-world examples like surfboards and drainage systems demonstrate how multiple additives work together
- Each additive serves a specific purpose - from cost reduction to environmental protection