The various types of plastics, their benefits, and applications (2/2)

Published On: 15 July 2022 Leestijd : 3 minutes

In Part 1, we explored "commodity plastics" such as polyethylene (PE), polypropylene (PP), and acrylonitrile butadiene styrene (ABS). These materials are widely used for applications where specific material properties are less critical to product performance.

In this second installment, we’ll delve into "engineering plastics," a category of materials known for superior mechanical and thermal properties. These high-performance plastics are often used as substitutes for traditional materials like metal, aluminum, wood, or glass in technical applications.

Polycarbonate (PC)

Advantages:
Polycarbonate is renowned for its combination of stiffness, strength, and toughness. It is one of the most transparent plastics available, offering numerous possibilities for coloration. With minimal shrinkage and negligible moisture absorption, it provides exceptional dimensional stability across a range of applications.

This material maintains high impact resistance, even in temperatures ranging from -100°C to +135°C. Its excellent UV stability makes it a prime choice for outdoor use.

Polycarbonate is available in specialized grades for enhanced scratch resistance, heat resistance, and UV stabilization. It is also offered in food-grade variants.

Applications: Lenses, interior and exterior lighting, mobile phone housings, electrical components, medical devices, drinking glasses, and greenhouse construction.

Considerations:

Susceptible to stress cracking under external pressures.
Relatively high material cost.
Contains Bisphenol A (BPA).
Limited chemical resistance.

Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS)

Advantages:
This blend combines the strength and heat resistance of polycarbonate with the flexibility and ease of processing associated with ABS. PC/ABS offers improved injection molding performance, greater toughness, and enhanced dimensional stability. It provides better heat resistance compared to ABS and superior impact resistance at low temperatures compared to PC alone.

Applications: Automotive components, electronics housings, and consumer goods requiring durability and aesthetic appeal.

Considerations:

May show flow lines or visible streaks on molded parts.
Less suitable for exposure to harsh chemicals or solvents.

Polyamide (PA)

Advantages:
Commonly referred to as nylon, polyamide comes in various forms (e.g., PA6, PA6.6, PA11, PA12), each with specific benefits. Nylon is characterized by high mechanical strength, stiffness, and impact resistance. For applications requiring greater rigidity, glass-filled nylon (e.g., PA30GF) can be used. Nylon is also highly resistant to oils, solvents, and weak acids or bases.

Applications: Swivel and conveyor wheels, gears, bearings, screws, pump components, under-the-hood automotive parts, and camera components.

Considerations:

Nylon is hygroscopic, meaning it absorbs moisture from the air or direct water contact. This affects its mechanical properties and dimensions. In drier conditions, it can lose moisture, becoming more brittle.
Poor performance in the presence of strong acids.

Polyoxymethylene (POM)

Advantages:
Also known as acetal, POM is valued for its toughness, stiffness, and strength. Its self-lubricating properties and low friction coefficient make it ideal for gears and moving parts. POM is resistant to fuels and organic solvents and does not absorb moisture, ensuring dimensional stability.

It maintains its mechanical properties in temperatures between -40°C and +80°C and is well-suited for secondary machining processes such as threading.

Applications: Gears, threaded bushings, pump impellers, conveyor belts, automotive switches, and electrical switch components.

Considerations:

Significant shrinkage during cooling requires a uniform wall thickness in product design.
The low friction coefficient makes it difficult to paint or coat.
POM-to-POM contact can produce a squeaking noise.

Next steps

While this article highlights key engineering plastics, there are many other materials, each with unique benefits and considerations. Choosing the right plastic for your application can be challenging, but expert guidance can simplify the process.