Fiber-reinforced plastics utilize two types of matrix materials: Thermoset and Thermoplastic. Though both matrices have been around since the dawn of the composites era, primary structural parts have been mainly manufactured using thermoset matrices due to their ease of processing.
However, since the emergence of thermoplastic additive manufacturing (commonly known as 3D printing) thermoplastic composites have created a new image of ease of processing and sustainability. There is now a growing trend toward the additive manufacturing of thermoplastic composites for primary structures.
The blog here focuses on introducing both types of matrices and their associated pros and cons for applications, ease of production, and sustainability. In this blog post, we are focusing on long-fiber composites only.
Thermoplastic Resin
Thermoplastics, like metals, softening and melting as more heat is applied, and re-hardening with cooling. This process of crossing the softening and/or melting threshold (Tg) can be repeated as often as desired without any appreciable effect on the material properties in either state. Typical thermoplastics used in structural composites parts include:
Acrylonitrile Butadiene Styrene (ABS)
Acrylonitrile Butadiene Styrene, often abbreviated as ABS, is an opaque engineering thermoplastic widely used in electronic housings, auto parts, consumer products, pipe fittings, Lego toys, and many more.
Polyaryletherketones (PAEK)
Polyaryletherketones (PAEK) are semicrystalline polymers. They exhibit good stability and mechanical strength at high temperatures. PAEK is extremely resistant to chemicals and hydrolysis, making them ideal for medical applications, oil drilling components, automotive gears, etc.
Polyetheretherketone (PEEK)
Polyetheretherketone (PEEK) is a semi-crystalline, high-performance engineering thermoplastic. This rigid opaque (grey) material offers a unique combination of mechanical properties, resistance to chemicals, wear, fatigue, and creep as well as exceptionally high-temperature resistance, up to 260°C (480°F). It is extensively used in demanding applications such as aerospace, automotive, electrical, medical, etc.
Advantages of Thermoplastic Composites
Thermoplastic composites offer two major advantages for some manufacturing applications: The first is that many thermoplastic composites have an increased impact resistance to comparable thermosets. (In some instances, the difference can be as much as 10 times the impact resistance.)
The other major advantage of thermoplastic composites is their ability to be rendered malleable. Raw thermoplastic resins are solid at room temperature, but when heat and pressure impregnate a reinforcing fiber, a physical change occurs (however, it isn't a chemical reaction that results in a permanent, nonreversible change). This is what allows thermoplastic composites to be re-formed and re-shaped.