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Know Your Materials: Flexible Polyurethane (FPU 50)

FPU 50 is an excellent, versatile choice for parts that require impact resistance, including 3D-printed hinges and friction fits.

Flexible polyurethane (FPU 50) is a resin material developed by Carbon® that is used in 3D printing. FPU 50 is a semi-rigid material with built-in elasticity that makes it resistant to abrasion, fatigue, and impact.

FPU hood prop

FPU 50 is made using Carbon’s Digital Light Synthesis (DLS)™ technology. The process forgoes traditional mechanical approaches to 3D printing — which can result in jagged edges and inconsistent quality — in favor of a gentler photochemical process that allows for a greater degree of control and fine-tuning. The process involves sending a continuous stream of UV images through a window that is both oxygen-permeable and UV-transparent into a liquid resin bath — the end result being an elastic and resilient material with unparalleled resolution and surface finish.

Designed with application versatility in mind, FPU 50 is an excellent material for manufacturing parts that need to be able to withstand repetitive stresses, such as friction fits, 3D-printed hinge mechanisms, or tough enclosures. It provides the strength to keep components fastened together or protected without sacrificing strength or flexibility.

Mechanical Specifications

FPU 50 is functionally similar to injection-molded polypropylene, pairing a moderate stiffness and high impact resistance with enough flexibility to make durable parts that hold up to a variety of forms of repeated contact. Here are a few key mechanical specifications of FPU 50:

  • Ultimate Tensile Strength: 29 ± 1 MPa
  • Elongation at Break: 280 ± 15%
  • Young’s Modulus: 860 ± 110 MPa
  • Impact Strength (notched): 40 ± 5 J/m
  • Heat Deflection Temperature: 78°C

For more information, peruse the Carbon FPU 50 datasheet.

Why FPU 50?

DLS allows for the large-scale production of high-quality parts, making FPU 50 a favorable option when looking to print hundreds or thousands of similar parts.

What’s more, FPU 50’s blend of strength and elasticity make it the additive manufacturing material of choice for a wide range of practical applications that require repeated bending or flexing.

Strain relief part made of FPU

Similar to materials like acrylonitrile butadiene styrene (ABS), FPU 50 is commonly used as an engineering plastic due to its resistance to fatigue. However, sunlight causes ABS to degrade, and other fatigue-resistant materials like polyether block amide (PEBA) are often too flexible and rubber-like for applications that require sturdier parts. Because of the limitations of these comparable resins, FPU 50 is often the ideal choice for parts requiring long-lasting durability.

Further, FPU 50 is resistant to chemical leaching, corrosion, freezing, most forms of physical damage, as well as most solvents and glues. 

Popular applications

Considering that FPU 50 is ideal for application in parts that undergo continual stress or pressure, the resin is often recommended for use on 3D-printed hinges or friction fits. Thanks to its resistance to impacts and abrasions, FPU 50 can also be used to create shield parts for the product assembly process.

FPU 50 is commonly used in the electronics industry for parts that encapsulate, insulate, or seal off components that are fragile or pressure-sensitive, such as circuit boards, microelectronics, and underwater cabling. However, FPU 50 has a lower heat deflection temperature than materials like Cyanate Ester and epoxy, so it is best suited to lower-heat applications.

snap fit made of FPU

Additionally, Snap Fit dental bands, re-closable fasteners, and camera mounts are all typically constructed from FPU 50, as each of these parts requires flexibility and impact resistance.

Getting started with FPU 50

FPU 50 offers a number of benefits in the production of parts that will be subject to repeated motions and bending, from 3D-printed hinges to component shield parts. And while materials like ABS and PEBA are useful for certain applications, FPU 50’s unique blend of durability, elasticity, and physical resistance make it the material of choice for many manufacturers.

At Fast Radius, we take pride in expanding the boundaries of what’s possible. Our experienced team of engineers work closely with clients to refine and perfect their designs, ensuring that each part serves its purpose effectively and efficiently. Think FPU 50 might be the right solution for your 3D-printed hinges or other parts? Contact us today to get started.

Ready to learn more? Look through our resource center to find out about other materials that can be used with Carbon technology and the DLS process, such as EPU and RPU 70.