Types of Plastics

Plastics come in thousands of varieties with different base chemistries, derivatives, and additives that are formulated to cover a wide range of functional and aesthetic properties.

To simplify the process of finding the material best suited for a given part or product, let’s look first at the two main types of plastic: thermoplastics and thermosets.

Thermoplastics

Thermoplastics are the most commonly used type of plastic. The main feature that sets them apart from thermosets is their ability to go through numerous melt and solidification cycles without significant degradation. Thermoplastics are usually supplied in the form of small pellets or sheets that are heated and formed into the desired shape using various manufacturing processes. The process is completely reversible, as no chemical bonding takes place, which makes recycling or melting and reusing thermoplastics feasible.

Common types of thermoplastic materials:

• Acrylic (PMMA)
• Acrylonitrile butadiene styrene (ABS)
• Polyamide (PA)
• Polylactic acid (PLA)
• Polycarbonate (PC)
• Polyether ether ketone (PEEK)
• Polyethylene (PE)
• Polypropylene (PP)
• Polyvinyl chloride (PVC)

Thermosetting Plastics

In contrast with thermoplastics, thermosetting plastics (also referred to as thermosets) remain in a permanent solid state after curing. Polymers in thermosetting materials cross-link during a curing process that is induced by heat, light, or suitable radiation. This curing process forms an irreversible chemical bond. Thermosetting plastics decompose when heated rather than melting, and will not reform upon cooling. Recycling thermosets or returning the material back into its base ingredients is not possible.

Common types of thermoplastic materials:

• Cyanate ester
• Epoxy
• Polyester
• Polyurethane
• Silicone
• Vulcanized rubber

Types of Manufacturing Processes

• 3D Printing
• CNC Machining
• Polymer Casting
• Rotational Molding
• Vacuum Forming
• Injection Molding
• Extrusion
• Blow Molding

Manufacturing Process

1. Print setup: Print preparation software is used for orienting and laying out models within a printer’s build volume, adding support structures (if needed), and slicing the supported model into layers.
2. Printing: The printing process depends on the type of 3D printing technology: fused deposition modeling (FDM) melts a plastic filament, stereolithography (SLA) cures liquid resin, and selective laser sintering (SLS) fuses powdered plastic.
3. Post-processing: When printing is complete, parts are removed from the printer, cleaned or washed, post-cured (depending on the technology), and the support structures removed (if applicable).

As 3D printers require no tooling and minimal setup time for a new design, the cost of producing a custom part is negligible in comparison with traditional manufacturing processes.

3D printing processes are generally slower and more labor-intensive than manufacturing processes used for mass production.

As 3D printing technologies improve, cost per part continues to fall, opening up a wider range of low- to mid-volume applications.

While most plastic manufacturing processes require expensive industrial machinery, dedicated facilities, and skilled operators, 3D printing allows companies to easily create plastic parts and prototypes in-house.

Compact desktop or benchtop 3D printing systems for creating plastic parts are affordable and require very little space and no special skills, enabling professional engineers, designers, and manufacturers to speed up iteration and production cycles from days or weeks to a few hours.

Materials

There are many types of 3D printers and 3D printing technologies on the market, and the available materials vary by technology.