Feature originally published on 13 September 2019 and updated online in September 2022. Roles, market observations and product examples below reflect the original interviews. PAEK is the correct name of the polymer family; the original “PEAK” spelling has been corrected.
Manufacturing technologies can be a true game changer in the production of parts if all components of the manufacturing process are used properly. Materials play a key role in this revolution: producers must not only find the appropriate material for their application; they also need to have a 3D printer that can process it.
The challenge is big as all types of materials are involved: metals, polymers, ceramics, concrete and biological cells. This article aims to observe the growing use of polymers in additive manufacturing. A key focus will be made on PAEK materials.
The use of PAEK materials
High-performance thermoplastics include polyaryletherketones (PAEK) and polyetherimide (PEI), among other families. ULTEM is a trade name associated with PEI. These examples do not constitute an exhaustive classification.
PEEK (polyetheretherketone) and PEKK (polyetherketoneketone) belong to the PAEK family. Suitable grades can be processed through techniques including laser sintering and material extrusion. Their thermal, mechanical and chemical properties depend on grade, processing and part design; a material name alone does not establish printability on a given machine.
In the original interview, Victrex’s Martin Court highlights the need to reach the processing temperature of the chosen PAEK grade and control cooling. The temperatures, heated environment and thermal history must be specified for that material and process. Victrex’s 2019 presentation distinguishes filament and powder offerings, while its 2020 announcement describes a PAEK formulation designed for AM.
Speaking specifically about PEEK, Martin Court explains: “PEEK differs from other polymers in that it is one of the highest performing thermoplastics available. Its excellent mechanical and chemical characteristics mean that it uniquely supports a combination of multiple requirements. For example, the versatile light weight, high strength PEEK polymer provides high resistance to wear, temperature, fatigue and aggressive fluids/chemicals.”
PAEK materials are considered for demanding applications in automotive, aerospace and medical manufacturing. In the 2019 interviews, Harold van Melick, then R&D Director at DSM Additive Manufacturing, describes the wider role of polymers: “Polymeric materials are widely used in many industries (maybe all industries). Although many applications are cost-driven mass-manufacturing (e.g. injection molding), in many cases the properties of the polymers are decisive in the choice of materials. For instance, it’s impossible to make a connector, a circuit breaker, a tyre, a flexible CVJ boot out of metals. This quest for functionality will drive designers to make applications out of polymers in many industries. The most obvious ones are medical/dental, transportation/automotive, electronics and sports.”
Matt Torosian also lays emphasis on the need to combine the economic point of view with technical requirements. According to the Director of Product Management for Materials at Jabil, OEMs have applications that they feel are a good commercial fit for polymer AM. The issue is, the material set available does not meet the physical requirements. “They have aligned on the DfAM benefits and quantities needed and cost model benefits but if the final part cannot meet the engineering requirements, the application will have to be redesigned into conventional processes where the material set is more aligned with the requirements.
If OEMs and all participants up and down the AM Supply Chain want to satisfy those customer requirements, we have to develop Materials, Process and Machines to meet those requirements. Leave one of those three critical pieces out, and you don’t have an ecosystem that can thrive”, adds Matt Torosian.
Matching materials, processes and applications
The maturity of an AM route depends on the application, material, machine and qualification evidence. Metal AM cannot be ranked above polymer AM in general. Van Melick points to weight, flexibility and the range of polymer properties as reasons to develop suitable materials and processes.
Victrex describes potential advantages of PEEK and other PAEKs: “compared to metals, PEEK-based materials are very light in weight, easily shaped, resistant to corrosion and can have considerably higher specific strength (strength per unit weight). In addition to that, potential benefits of using members of the PAEK family of polymers for AM could also include in the future: – improved economics through elimination of machining waste, improved refresh rates in powder bed fusion (PBF), and improved material utilisation in filament fusion (FF) or – patient customized implants and improved outcomes through new features and better fit.”
These are application-dependent possibilities. Specific strength, material use and clinical outcomes require separate comparisons and evidence; they do not follow automatically from choosing a PAEK.
Jabil’s assessment of the supplier landscape in the original interviews is: “Polymer materials in the Additive Manufacturing market, especially powders for SLS and HSS are restrained by a lack of participants. As new applications have emerged, the number of Engineered Materials available has not significantly changed. Beyond the resin producers that offer 3-10 grades of SLS powders each, only a handful of producers globally produce reinforced, custom engineered powder products for SLS. If you compare that to the conventional polymer process market, injection molding and extrusion, there are literally hundreds of compounders that fill that need in the AM market. Therefore, companies are investing to fill that gap in the fundamental building block of functional parts i.e. polymer materials. In relation to metals, the number of materials involved in polymer AM is much fewer. Also, in metals, there is an established market for powdered metals.”
The range of qualified AM materials is narrower than the full range available to conventional polymer processing. The original article’s unsourced “1%” estimate is not used as a market measurement. Qualification must consider the combined material, process and machine.
Let’s speak about the thermoplastic PEEK
PEEK is valued for its mechanical performance, chemical resistance and high-temperature capability. Flammability behaviour also depends on grade, thickness and test conditions. Printed parts do not automatically reproduce moulded-material data: orientation, porosity, thermal history and post-processing matter. Polyamides, polyesters, PPA, PPS and other polymers offer different compromises, so selection starts with application requirements.
A huge potential for the medical sector
AM can help manufacture patient-specific implants, but neither customisation nor the use of PEEK establishes clinical suitability. PEEK has applications in areas such as spinal and trauma devices; this does not make it the most widely used material for every implant.
The original report presents the following description of Invibio’s PEEK-OPTIMA offering: “Victrex’s medical business, enables artefact-free monitoring and assessment of patient healing sites. Additionally, PEEK has a modulus closer to bone which, compared with metal, which helps minimize stress shielding and stimulate bone on growth.”
This statement needs qualification: radiolucency, stiffness and bone attachment vary with formulation and implant design. Invibio distinguishes unfilled, reinforced and hydroxyapatite-enhanced grades. Bone ongrowth should not be assumed for every unmodified PEEK surface, and use of a material does not validate a printed medical device or guarantee patient outcomes.
The few issues that need to be tackled
Developing PAEK applications requires compatible materials, processes and machines. Jabil’s Matt Torosian argues for independent suppliers: “the Polymer materials market needs more entrants that are open and independent of machine manufacturers and the entire machine manufacturers’ supply chain. When you link the material supplier to the machine supplier, you limit the ability for OEMs and Processors to optimize and innovate both the material and the process. This in turn limits innovation at the machine level because they are not pushed to develop new machine technology to fit an ever-changing materials and process landscape.
If you look at this like conventional processes, the independence of compounders, resin producers, mold makers and machine producers has propelled the technology to its current state. The four critical aspects of the process continuously expand the envelope of what can be done, pushing each other to innovate and to be able to use a unique material, complex tools or machine technology that exploit some attributes previously not possible by the current state of the technology. Our feeling is, the market always wins when it is not restricted. Open platforms and markets should be the focus of the AM ecosystem in order to reach the maximum level of innovation and adoption.”
DSM emphasises translating intended use into technical specifications. Its proposed starting point is “the way one translates the application requirements into material properties (that determines material selection) and a 3D printing technology that will be able to convert those materials.”
Standardization of materials
Standards help stakeholders specify materials, test methods and qualification requirements consistently. They support quality control but do not guarantee the performance of a particular part. Manufacturers still need to identify the standards applicable to the process and end use, establish acceptance criteria and demonstrate repeatability.
Initially published on September 13, 2019.
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