Polymers are everywhere. They are substances – organic or synthetic – composed of strings of monomers called macromolecules. Polymers make up many of the materials in living organisms, including, for example, proteins, cellulose, and nucleic acids. But for our purposes, we will focus on synthetic, petroleum-based polymers – plastics.
Broadly speaking, plastics can be split into two groups: thermosets and thermoplastics. Both have unique characteristics and both can be 3D printed, though the processes are very different.
Thermoplastics are that group of plastics defined by intermolecular forces that weaken substantially with increased temperature. This means that when heated, melted, formed and allowed to cool, retain all of their essential properties. The list of thermoplastics is extensive and includes such commonly used plastics as ABS, Nylon, PVC, Polycarbonate and a great many others. Because of this quality, most thermoplastics can be reclaimed and recycled.
Thermoplastics in 3D printing have gained a lot of exposure because this group of plastics is used in Fused Deposition Modeling, which is the most popular form of 3D printing currently in the market.
Each of the plastics have been engineered to suit a particular need whether it be cost effectiveness, chemical resistance, aesthetics, physical properties such as impact resistance and strength, heat resistance and so on. It is important to understand the pros and cons each plastic offers before use. For example, ABS offers good strength and heat resistance but is known to emit volatile organic compounds when 3D printed and is not considered food safe.
The term ‘thermoset’ may not be as popularly known as ‘thermoplastic’, but thermoset polymers are equally popular and includes epoxy, silicone, melamine, and Bakelite – the first fully synthetic, heat resistant and non-conductive plastic.
Thermosets differ from thermoplastics primarily in that once cured or hardened, they can no longer be reshaped or reverted to their previous form. Thermosets begin as a viscous liquid that is then subjected to a catalyzing agent like heat or radiation. Thermoset plastic properties are generally include increased strength and heat resistance when compared to thermoplastics due to their crosslinking (three-dimensional network of bonds. The crosslinking density can be improved further, which enhances the mechanical strength, heat resistance and hardness.
This combination of properties makes them ideal for use in construction equipment panels, electrical housings and components, insulators, cell tower tops, heat shields, circuit breakers, agricultural feeding troughs, motor components, and disc brake pistons.
In short, thermosets and their composites can be found in all markets and sectors.
POLYMERS…AND 3D PRINTING
Given the differences between thermoplastics and thermosets, it should not come as a surprise that they are each better suited to different types of 3D printing. Because thermoplastics can be formed with the application of heat, they have been ideally suited for Fused Deposition Modeling 3D printing which has rapidly become one of the most popular forms of 3D printing currently in use. Selective Laser Sintering has also evolved as a viable 3D printing method for powdered thermoplastics. Thermosets are best suit to vat polymerization 3D printing techniques like SLA (Stereolithography) and DLP (Digital Light Processing).
More information on each method and the various materials that can be used for each can be found by selecting the links provided.