by Melissa Donovan
Filaments, powders, and resins are all integral to the creation of three-dimensional (3D) builds. As further advancements in these materials occur, their defined feature sets become integral to meet the demands of the industries using the technology. In particular, there is increased interest in flame retardant (FR) resins and powders. Most notably, aerospace; transportation—automotive, trains, boats; electronics; and even the medical field require FR materials.
“The demand for FR resins has drastically increased among industries looking to leverage in-house additive manufacturing (AM) for all steps of the production process. Many industries commonly integrate some type of 3D printing into prototyping workflows, but often have to move to traditional manufacturing methods while still in the development stage in order to comply with regulatory requirements for flammability. With FR resin, large businesses can not only improve their development timelines, but also use a common material across teams, from design to maintenance and repair operations, as well as manufacturing fixtures,” proposes Elena Austras, product marketing manager, Formlabs.
3D printing on its own offers a host of benefits, from cost efficiency and durability to faster design production. Hason Rolland, SVP of materials, Carbon, says, “adding flame retardancy to the list ensures that manufacturing, electrical, healthcare, and aerospace specialists, among others, are provided with the safest equipment and products possible.”
Keeping it Beneficial
With demand for FR resins and powders deriving from a number of industries and applications, many are poised to benefit.
“For the applications in transportation or consumer goods FR materials are necessary for safety reasons. The associated certifications are required to enable products to be sellable or to pass transportation safety regulations. This is part of the natural progression of applications moving from functional prototyping into more end-use applications, which come with increasing requirements. This is a good indication that we are progressing into more challenging areas,” notes Aric Yackly, product manager, P3, Stratasys.
According to Steven Kubiak, process engineering manager, Jabil Inc., “anywhere the benefits of additive intersect with an FR need will benefit. FR powders will benefit the same way general powders will benefit.”
“With FR resin, users easily and quickly create stiff, creep resistant, and functional plastic parts that perform well long term in high temperature environments without turning to injected molding. FR resin is ideal for producing airplane, automobile, and railway interior parts; protective and internal consumer electronics components; and custom jigs, fixtures, and replacement parts for industrial environments or ignition sources,” shares Austras.
Nirup Nagabandi, VP of materials and process engineering, Essentium Inc., notes how “FR resins and powders serve as a game changer by significantly reducing the risk of fire incidents and enhancing overall safety measures.”
The 3D Process
3D printing processes like fused deposition modeling (FDM), digital light processing (DLP), stereolithography (SLA), and masked stereolithography (LCD) all use FR materials.
“Theoretically, a new process could be designed for these materials. That being said, FR resins/powders are perfectly capable of being processed with common, commercially available 3D printing processes today,” suggests Sylvia Monsheimer, head of industrial 3D printing, Evonik.
In Yackly’s experience, FR materials are developed for both thermoplastic and photopolymer thermosets and are becoming available on an increasing range of systems, with FDM and DLP as the leading technologies.
“All printing processes produce parts in FR material, but the amount and type of additive or modifier to the polymer will depend on the process,” explains Kubiak.
Photocentric Inc. started testing its FR resin on some UV DLP and LCD-based systems to fully validate it.
Formlabs’ FR resin is compatible with SLA printers. “For many industries, maintenance and repair parts have to be ordered to ensure the product remains compliant. SLA 3D printing was not traditionally a viable option, despite its low cost per part and efficiency. With FR resin, SLA 3D printing can finally be deployed as an on demand repair part manufacturing solution,” shares Austras.
According to the company, Essentium Duratem can be used with any open eco-system high-temperature 3D printing machine, including the Essentium High-Speed Extrusion 180 HT and HSE 280i HT 3D printing platforms.
Carbon EPX 86FR works best on Carbon DLS printers, such as the M2, M3, M3 Max, and L1.
Standards are in place to certify whether a resin or powder is FR.
Certification depends on the industry and application. For example, FR materials used in consumer electronics are certified by the Underwriters Laboratories (UL), whereas FR grades for aerospace applications require testing to a different burn standard and are certified in conjunction with the aircraft manufacturer in question and the FAA, shares Kubiak.
UL 94 is a plastics flammability standard released by the UL. “One common standard for assessing plastics flammability is UL 94. There are varying degrees of FR that get assessed by the orientation of the part in the flame, the thickness it will pass the test at, burn rate, and whether or not it will drip flammable plastic drops or not,” explains Yackly.
Another standard to comply with is the FAR 25.853(a) regulation. Carbon EPX 86FR achieves a 12 second burn compliance for a thickness of one millimeter. It is also accredited for UL 94 rating at a two millimeter thickness.
Formlabs’ FR resin is halogen-free, UL 94 and FAR 25.853(a) certified with favorable flame, smoke, and toxicity (FST) ratings. FR resin produces 3D printed parts that meet necessary certification requirements for enduring hazardous environments, according to the company.
“Our FR materials undergo rigorous testing and certification processes to ensure their FR properties. Essentium’s certificate of conformance provides individual spool traceability through the ISO and AS9100 quality process. Essentium is working with customers, including the U.S. Air Force, to certify materials for uniform, repeatable, and reliable part production. These certifications validate the flame retardancy of our materials, providing confidence to our customers in their safety performance,” explains Nagabandi.
FR resins and powders cost more. However, the applications that deem flame retardancy as a critical feature make it so the purpose outweighs the cost.
Development can be challenging, which increases pricing. “The development cost of the material itself needs to be recaptured, and assuring FR performance out of printed parts is a challenging technical problem,” explains Kubiak.
Manufacturing a FR resin or powder can be more complicated, which effects cost. “Various additives must be integrated into the material, requiring additional process steps,” says Kubiak.
“Typically FR materials carry a premium over standard materials due to the additional cost of additives as well as the development cost to create and process 3D printable materials that have the right mix of temperature, mechanical, and FR performance,” agrees Yackly.
Continued quality control, to ensure the customer that the additive will perform as expected—in this case with FR properities, also enhances the cost of these resins and powders, according to Monsheimer.
The investment incurred to test and certify an FR material also means the end user pays more, according to Kubiak.
Despite the high costs for FR materials, a representative from Photocentric notes that the pricing is no different than other engineering grades of materials. Further noting the desire “to make AM accessible and applicable to all.”
Also, when comparing AM to traditional manufacturing process like injection molding, FR materials are less expensive. “FR resin unlocks design freedom to create isotropic and highly detailed parts with an excellent surface finish that have the look and feel of injection molded parts but at much lower cost. It also helps to accelerate time to market without the design constraints and high costs of its injection molding or casting counterparts,” notes Austras.
“The investment in FR materials is justified by the significant risk reduction and enhanced safety they offer, which outweighs the incremental cost,” notes Nagabandi.
It is because of the higher costs and need for certification that Kubiak believes all resins and powders will not be FR in the future.
Similar to what occurred in the injection molded plastics world, Yackly also doesn’t see all resins and powders being FR nor passing all FR tests. “Many 3D printing materials today already pass the basic horizontal burn tests, but as far as the more stringent FR requirements products will be targeted to an application. In the future I expect many more materials to be aligned to increasingly specific applications with their own set of requirements.”
“While certain industries rely on FR resins to meet strict production regulations, not all AM printing processes and materials require or are conducive to the same characteristics held by this type of resin,” adds Austras.
Keeping in mind that demand for FR materials may grow, Nagabandi suggests “a wider range of resins and powders may have FR properties in the future.”
“The next generation of resins and powders will build upon recent software models and I expect that flame resistance will remain a top priority for developers,” adds Rolland.
Carbon EPX 86FR is a photopolymer resin that offers a combination of FR, functional toughness, high strength, and long-term stability. It features dual cure chemistry, utilizing a print and bake process.
Evonik offers INFINAM R TPC, an elastomeric copolyester that exhibits excellent flexibility, durability, and resistance to abrasion, chemicals, and UV radiation-—in addition to being FR.
Essentium Duratem, one of the company’s newest materials, can withstand temperatures of 150°C and is resistant to FST and passed FAR 25.853 FST testing. The material is suitable for a range of applications, from aerospace parts to maintenance uses such as replacing clamping blocks and switch covers. It is also ideal for railway components, including ventilators and covers.
At RAPID + TCT 2023, Formlabs introduced its Flame Retardant Resin, which is its first UL 94 certified resin and first self-extinguishing material. Formlabs is looking forward to expanding its portfolio of FR certified-resins to broaden printing capabilities for the many industries that rely on durable components that can withstand high temperature environments.
Jabil’s FR additive polymer currently is the PC 1500 FR, which is an FR polycarbonate filament. Made from UL V-0 Yellow Card certified raw materials, Jabil’s PC 1500 FR can be printed on direct drive and bowden tube 3D printers. This material, with its FR properties, is used in the aerospace and automotive industries.
Photocentric was planning to announce a new FR material at press time.
At Stratasys some of its more advanced FR/FST materials are Loctite 3D 3955 FST, Kimya PC-FR, Addigy PA6/66-GF20 FR LS, and Ultem 9085 resin.
The introduction of FR resins and powders in 3D printing means users who relied on injection molding for many of their builds no longer have to implement that as part of the process. In turn, more industries are introduced to the advantages of AM. Meeting requirements like flame retardancy for specific applications is a sign that AM is maturing as an industry.
Sep2023, Industrial Print Magazine