Plastics (Leaving Cert Construction Studies): Revision Notes
Plastics
Plastics are artificial materials that have become increasingly popular in the building industry. They offer a lightweight, low-maintenance alternative to traditional materials like wood and metal. The construction sector now uses plastics extensively for various applications including plumbing systems, piping, windows, doors and electrical ducting.
The widespread adoption of plastics in construction represents a major shift towards more versatile and sustainable building materials. Their ability to replace traditional materials like wood and metal in many applications has revolutionised modern construction practices.
Advantages of using plastics
Plastics offer numerous benefits that make them attractive alternatives to traditional building materials:
Manufacturing and installation benefits:
- Simple to manufacture into various shapes and forms
- Straightforward to install, reducing labour time and costs
Durability properties:
- Excellent resistance to water damage
- Will not rot like natural materials
- Cannot rust like metal components
Performance characteristics:
- Provide effective thermal insulation
- Offer electrical insulation properties
- Available in both rigid and flexible forms
- Can be manufactured as opaque or transparent materials
- Many types are fully recyclable
Practical Application: PVC Window Frames
Traditional wooden window frames require regular painting and maintenance to prevent rot and weather damage. PVC window frames, however, provide:
- No painting or staining required
- Excellent weather resistance for 20+ years
- Superior thermal insulation properties
- Complete recyclability at end of life
Disadvantages of plastics
Despite their benefits, plastics do have some limitations in construction applications:
- Discolouration: Can fade or change colour when exposed to UV light over time
- Brittleness: Some types become brittle, especially in cold conditions
- Limited recycling: Not all plastic types can be recycled effectively
- Environmental concerns: Manufacturing processes can release harmful gases
While plastics offer many advantages, it's crucial to consider their environmental impact and select appropriate types for each application. Some plastics may not be suitable for high-UV environments or extreme temperature conditions.
Understanding polymers
The technically correct term for plastics is 'polymers'. In construction, there are two main categories of polymers that are particularly important to understand.
Two Main Categories of Polymers: Understanding the difference between thermosetting and thermoplastic polymers is essential for selecting the right material for each construction application.
Thermosetting polymers
These polymers undergo a chemical change when first heated and moulded. Once they have set into their final shape, they cannot be reshaped or remoulded, even when reheated.
Epoxy resins
- Combined with hardening agents to create extremely durable plastic materials
- Essential component in fibreglass manufacturing, where they bind glass fibres together
- Commonly used for high-strength applications requiring chemical resistance
Polyurethane
- Frequently used as foam insulation for hot water storage tanks
- Available in liquid form as a protective varnish coating for timber
- Provides excellent thermal insulation properties
Worked Example: Fibreglass Manufacturing
Step 1: Glass fibres are laid in the desired pattern Step 2: Epoxy resin is mixed with hardening agent Step 3: Resin mixture is applied to bind the fibres Step 4: Once cured, the material becomes permanently rigid and cannot be reshaped
Thermoplastic polymers
These polymers can be repeatedly heated and reshaped into different forms. This makes them highly versatile and recyclable.
Acrylic
- Manufactured in sheet form as a lightweight alternative to glass
- Can be moulded when heated to create items like bathtubs
- Offers excellent clarity and weather resistance
Polythene/polyethylene
- Widely used in packaging applications
- Functions as effective damp-proof membrane material
- Can be formed into rigid items such as paint containers and storage boxes
Polystyrene
- Primarily used in foam form for insulation applications
- Lightweight and provides good thermal insulation
- Common in cavity wall insulation and packaging
Polyvinyl chloride (PVC)
- Extensively used for manufacturing doors and window frames
- Provides electrical insulation for cables and wiring
- Durable and weather-resistant
Polypropylene
- Used in rope and carpet manufacturing
- Offers good chemical resistance and flexibility
- Lightweight yet strong material
Thermoplastic polymers' ability to be repeatedly heated and reformed makes them ideal for recycling programmes. This characteristic allows waste plastic materials to be processed into new products, supporting sustainable construction practices.
Key Points to Remember:
- Polymers are the correct technical term for plastics in construction
- Thermosetting polymers set permanently and cannot be reshaped once moulded
- Thermoplastic polymers can be repeatedly heated and remoulded, making them recyclable
- Plastics offer excellent resistance to water, rot and rust compared to traditional materials
- Common applications include plumbing, electrical systems, windows and insulation