In the past year, the range of 3D printing filaments has exploded, bringing masses of new materials to the market. Here, we take a look at a few different plastics, new and already established, to consider what goes in to each type of filament, how they perform from user and environmental perspectives and what their ideal applications could be.
First, a little background on us – although we develop, make and sell polyolefin 3D printing filaments through our company – Forefront Filament, we actually have a history in more traditional manufacturing circles. We have worked with polymer producers (chemical companies), converters (moulding, extrusion, thermoforming, machining) and brand companies, helping them to make better plastic choices. By better, we mean better for them (performance, processing, price), better for the end user (performance, aesthetics) and better for the world (all-round environmental performance). So here are our thoughts on some FDM materials:
Let’s start with one of the most popular materials – Polylactic Acid (PLA). This stuff is a “biopolymer”, which means it comes from renewable resources such as corn or potato starch. That’s great from an environmental viewpoint, so long as the starch is responsibly sourced, without depriving local economies from producing food on the same land.
PLA is easy to print and biodegradable (under controlled conditions), but parts printed with PLA leave much to be desired. PLA parts feel brittle, scratchy, with sharp corners and poor strength. It’s good for printing ornaments, but doesn’t find wide use in industrial 3D printing or in a wider world of products made from plastic.
Given the environmental attractiveness but physical limitations of PLA, many companies have begun producing modifications of PLA – for impact improvement, flexibility, softer edges and special effects. The thing about PLA is that, as a pure material, it offers none of these features - which means that these brands are adding other materials to give it impact improvement, flexibility etc. On closer inspection, there’s often no technical or safety data on what is being added to obtain these properties and so it’s difficult to be sure that the benefits of the base material are not negatively affected.
Now to the other most popular printing material – Acrylonitrile Butadiene Styrene (ABS). ABS is used in injection moulding to create hard cases and enclosures for some electrical products, and is the material that Lego is made from. It is a rigid, hard material that is not as brittle as PLA, so in 3D printing it has become the first choice for printing functional parts with higher temperature resistance and impact resistance, though in comparison to the range of materials now available it is still fairly brittle.
In terms of print experience, ABS can be difficult to use. It has a tendency to warp, and so requires good bed-plate adhesion and enclosed build chambers for best results. The other notable aspect of the ABS print experience is the smell. ABS contains styrene, along with some other toxic components, which can be released at high temperatures. Ventilation is a must, good quality filters are recommended, and it is advisable to avoid long-term exposure. It is particularly surprising, therefore, that 3D printing pens targeted at children are designed to accept ABS filaments.
In environmental performance, ABS can’t easily be recycled and, when it is, it loses much of its mechanical strength, lowering its value for production.
Luckily, there are now a plethora of other FDM material options offering similar or better performance to ABS (see Engineering Grades below).
Whether it is labelled TPE or TPU, most flexible filaments are made partly or entirely from thermoplastic polyurethane (TPU). In industry, TPU finds application in shoe soles, artificial leather and drive belts, for example. Unlike other polymers that are generally processed from pellets (small plastic beads), polyurethane is made using a mixture of liquids called polyols and isocyanates. These are dangerous chemicals to handle, so it’s a good job that TPU comes to you in the form of a filament. However, given the ingredients, just as with ABS, it is best to avoid exposure to fumes that could be emitted during printing.
TPU is another plastic (like ABS) that sits in recycling code 7 – which means it generally isn’t recycled. In industry, TPU recycling tends to involve chopping it up and gluing it back together to make carpet underlay, sports surfaces etc. But as an option for 3D printing, it offered the first opportunity to print something that wasn’t rigid, so it still has its place.
The fastest growing sector of FDM materials is in “engineering grade” polymers. These are filaments that can easily rival ABS for performance-in-use, offering durability, strength and resistance to impact, high temperature and chemicals. Unfortunately, for most of these options, “chemical” resistance doesn’t include resistance to water and moisture ingress, so, like PLA and ABS, these filaments need to be stored with desiccant or dried before printing.
Some engineering grade plastics have familiar names – nylon, PET, polycarbonate (PC). Some, like PET, are highly recyclable (code 1), and some are very mechanically strong, like PC. The choice of one engineering grade over another comes down to the needs of the particular application.
There is another range of engineering grades, however, that are just coming to the fore. These polymers could be considered to be the holy grail of 3D printing filament. They are safe – containing and emitting no toxic fumes, they offer durability, strength, impact resistance, chemical resistance and high temperature performance. They are easily recyclable and more energy efficient than PET to produce. They are easy to print and fully water- and moisture-repellent. They are polyolefins.
Polyolefins are a group of thermoplastic polymers that include polypropylene, polyethylene and mixtures of the two. They can be engineered to suit any manufacturing process and are widely used for consumer products in food service, medical, sports, household and children’s toys. They can be tough or rubbery, flexible, strong, or soft, depending on the formulation, without the need for additives.
We think that polyolefinic filaments have the potential to meet all of the needs and wants of 3D printing engineers, dabblers and enthusiasts. We at Forefront Filament have already released our first two grades of polyolefin engineering filament and both are based on polypropylene (PP) – F43 TOUGH for durable, strong prints, and F41 FLEX – an environmentally-friendly flexible.
If you would like to know more about how our filaments could perform for your application, please contact us.