Plastics: Under the Microscope
Some Commonly Used Plastics in Injection Moulding
The 10 most common materials used for injection moulding are:
- Polypropylene (PP): A versatile thermoplastic with high impact resistance and good chemical resistance.
- High-Density Polyethylene (HDPE): Known for its excellent strength-to-density ratio and resistance to chemicals and moisture.
- Acrylonitrile Butadiene Styrene (ABS): A rigid, durable plastic with good impact resistance, commonly used for consumer products.
- Polystyrene (PS): A lightweight, inexpensive material used for disposable products, packaging, and insulation.
- Polyethylene Terephthalate (PET): Commonly used for bottles and containers due to its clarity, toughness, and moisture resistance.
- Polyvinyl Chloride (PVC): A versatile plastic known for its durability, low cost, and resistance to chemicals and weathering.
- Nylon (PA): Exhibits excellent mechanical properties, heat resistance, and can be used for engineering applications.
- Polycarbonate (PC): Offers high impact resistance, transparency, and thermal stability, frequently used in automotive and electronic applications.
- Polyoxymethylene (POM): Known as acetal or Delrin, it has excellent mechanical properties, low friction, and high dimensional stability.
- Low-Density Polyethylene (LDPE): A flexible plastic with good impact strength, commonly used for packaging and film applications.
These materials cover a wide range of properties, making them suitable for various applications in industries such as automotive, consumer goods, electronics, packaging, and more.
The Importance of Selecting the Right Plastic for Injection Moulding
Choosing the right type of plastic for injection moulding is crucial for several reasons:
- Material properties: Each type of plastic has different physical, chemical, thermal, and mechanical properties. The specific requirements of the part (i.e. strength, flexibility, durability, chemical resistance, heat resistance, and electrical conductivity) need to be considered before the plastic is selected. This is essential to ensure that the final product will have the desired characteristics and will perform well under the intended conditions.
- Cost-effectiveness: Plastic materials vary in terms of cost. While some plastics may be cheaper, they may not possess the necessary characteristics for the intended use, resulting in poor quality or failures. On the other hand, using expensive plastics without justification can significantly increase the cost of production. Therefore, it is essential to strike a balance between the desired properties and the cost of the plastic material.
- Manufacturing constraints: Injection moulding is a highly automated and efficient manufacturing process. However, different plastics have different melt temperatures, flow rates, and shrinkage rates, which can affect the moulding process. The selected plastic should be compatible with the moulding equipment and its process parameters, ensuring smooth and consistent production without defects or wastage.
- Environmental considerations: Choosing a plastic that is recyclable, biodegradable, or made from renewable sources can help to reduce environmental footprint. Some industries and applications may also have specific regulations or standards with regard to the type of plastic allowed, especially in industries like automotive, medical, and food packaging.
- Safety and regulations: Industries such as aerospace and medical have strict safety requirements for their products. The chosen plastic must comply with these standards to ensure the safety of the end-users. It is important to consider factors such as toxicity, flammability, and chemical resistance when selecting a plastic for these applications.
The Benefits of Using Plastic in Manufacturing
There are several benefits of using plastic to manufacture parts:
- Cost-effective: Plastic is generally a more affordable material compared to metals or other materials. Therefore, plastic parts are relatively inexpensive to manufacture, making them a cost-effective solution for industries.
- Versatility: Plastic can be moulded into various shapes and sizes, providing designers and engineers with significant flexibility in manufacturing. It allows for complex geometries and intricate designs that may not be possible with other materials.
- Corrosion resistance: Unlike metal parts, plastic is resistant to corrosion caused by moisture, chemicals, or other environmental factors. This makes plastic parts more durable and longer lasting, reducing the need for maintenance or replacement.
- Electrical insulation: Plastic is an excellent electrical insulator, making it ideal for applications requiring electrical components. It helps prevent short circuits, insulation breakdown, and electrical failures in various industries.
- Design options: Plastic parts offer a wide range of design options, including various colours, textures, and finishes. This allows manufacturers to create visually appealing products or parts that match the brand’s aesthetics.
- Chemical resistance: Plastic is resistant to a wide range of chemicals, making it suitable for applications exposed to harsh environments or aggressive chemicals. It can withstand exposure to acids, bases, solvents, oils, and more.
- Reduced manufacturing time: Plastic parts can be produced through various manufacturing processes like injection moulding, which is a fast and efficient method. This helps in reducing manufacturing lead times and meeting production demands.
- Energy efficient: The manufacturing processes of plastic parts generally consume less energy compared to other materials like metals. This energy efficiency contributes to lower production costs and reduced environmental impact.
- Recyclability: Plastic is often recyclable, and using recycled plastic in manufacturing can reduce dependence on raw materials, promote sustainability, and minimise landfill waste.