Advanced materials are shaping the future of polymer-based additive manufacturing
Composites, high-performance polymers and 4D printed materials are pushing additive manufacturing to new heights
Though for years polymer-based 3D printing technologies were either regarded as limited to prototyping applications or to the low-demand maker community, recent developments both on the hardware and materials fronts are helping the technology establish itself as a key resource for advanced industrial applications. Playing an important role in this diversification is a group of high performance materials, known broadly as advanced polymers.
These materials, which include various composites and industrial plastics like PAEK (Polyaryletherketone) family polymers, are enabling manufacturers to 3D print functional prototypes and even end-use parts for a range of industrial applications—something which had previously been a challenge using thermoplastic filament extrusion (FDM/FFF) machines.
Across the industry, chemical and materials companies are increasingly developing advanced materials—which have largely been established in industrial manufacturing for years—specifically for use in additive manufacturing. Many 3D printer hardware manufacturers are also working closely with these companies to adapt the 3D printing hardware for the materials, ultimately seeking optimization on both fronts.
It is through this collaborative nature of the industry that we are today seeing new possibilities for additive manufacturing and advanced polymers. And though the landscape for these materials is changing on a regular basis, here is a snapshot of the current state of advanced materials and their applications.
Composites
The first group of advanced materials for AM we’ll look at is composites, which are a group of materials made up of a thermoplastic matrix and reinforcing fibers. Presently, composites for 3D printing are often reinforced with carbon fibers, glass fibers or Kevlar fibers.
These materials, available as powders, pellets or filaments, most commonly feature chopped fibers, though continuous fiber composite printing is being explored more and more. The main draw of using composite materials for production parts or functional prototypes is that the materials offer high strength and other high-performance properties (often comparable to metals) but without the cost or weight of working with metal materials.
Current challenges that exist in 3D printing composite materials are figuring out the most optimal way to align and integrate the fibers into the thermoplastic matrix and developing more robust 3D printers and extrusion mechanisms to process the hardy materials. Still, many companies are forging ahead with the development of composite materials and 3D printing systems, making composite-based additive manufacturing more viable every day.
Some of the key players in composite 3D printing today are Markforged, Stratasys, EnvisionTEC, Continuous Composites 3D, Arevo Labs, Impossible Objects, Cincinnati Inc., and others—and that’s only on the hardware front.
High-performance polymers
Perhaps most notable in the category of high-performance polymers are the PAEK family of materials, which comprise of PEEK, PEKK and PEI (also known as ULTEM). These materials, which are well established in traditional manufacturing (but are very difficult to shape using traditional formative technologies), offer a number of attractive qualities, like high-stress resistance and strength. The PAEK family of materials are also characterized by a high melt temperature of 400°C, which is good for heat (and fire) resistance but makes them more challenging to process than standard 3D printing materials.
The emergence of high-performance polymers adapted for additive manufacturing is expected to drive the adoption of 3D printing forward for industrial applications. The PAEK family of materials alone have applications in commercial aerospace, medical, automotive and more.
It is worth noting that materials such as PEEK and PEKK are being adapted for different 3D printing technologies, namely powder-based systems and deposition-based machines. PEEK is well suited for FDM/FFF 3D printing because of its low moisture absorption, though it does require higher operating temperatures than traditional filaments.
Presently, a small number of companies offer or are developing PAEK family materials for the FDM process. They include Solvay, SABIC, Victrex, 3DXTECH, 3D4Makers, Lehmann & Voss, and TreeD Filaments (note that this is not an exhaustive list).
In the powder market, PEEK and PEKK high-performance powders are expected to become widely adopted for end-use parts in the near future. Presently, however, offerings for powders are rather limited. EOS is one company that offers a PEEK material certified for its polymer powder bed fusion technology, through a range of other third-party powders have been successfully used on EOS machines. Other key players in the PAEK family powder manufacturing business are Germany-based RAUCH, Evonik and Oxford Performance Materials.
4D printed materials
Still very much in a development stage are 4D printed materials, so called because they integrate the element of time and movement into their behaviour. Some of the most commonly explored 4D printing materials are shape-memory polymers, which are polymeric smart materials that can be printed in one state and transform into another when exposed to a particular stimuli, such as heat, humidity or light. These characteristics make it possible to produce self-assembling structures.
Additive manufacturing has proven to be well suited for producing objects that can morph, largely because it can precisely deposit rigid and transformable materials in a way that researchers can control and predict the ultimate transformation. Presently, there are a number of research groups working on the advancement of 4D printed materials and their applications. The concept itself was pioneered at the MIT Self-Assembly Lab by Skylar Tibbits, who continues to advance the still experimental materials group.
Increasingly advanced materials
Though these are the three main groups of advanced materials—and though there is still a ways to go before they are all widely adopted and exploited—who is to say what other, new materials will be created or adapted for additive manufacturing in the future. We can look to graphene composites for an example of something that is within the realm of possibility and would hold numerous advantages. Another notable avenue is the development of bio-inspired materials.
It is also worth noting that within the sphere of polymer 3D printing, the industry didn’t jump from materials like PLA and ABS straight to composites and PEEK. There are a number of currently adopted materials which, while not strictly advanced materials, have become recognized industrially. These materials, including Nylon, PP, PC and some others, will likely remain as the dominant group of industrial polymers until the advanced materials we’ve outlined here are more broadly accessible.
