Choosing the Best Plastics for Bonded Manifolds

Edited for clarity and format on March 28, 2024

 

Bonded manifolds offer a variety of benefits. Ease of design flexibility means manufacturers like Controlled Fluidics can create intricate channels in almost any configuration.

Controlled Fluidics’ low-pressure bonding technology means channels retain their shape throughout the bonding process. The strength of the bond itself is another advantage. Capable of handling pressures to 150 psi, the bond is permanent and difficult to detect with the naked eye.

The best plastic for you will depend on the usage of your manifold. Here are some customer favorites:

Ultem®

UltemDue to its high performance and ease of manufacturing, ULTEM® is an excellent choice for manifolds, electrical insulators, reusable machined components, electrical component housings, and aircraft instrumentation. This plastic combines exceptional strength and rigidity with superior thermal properties, such as outstanding heat resistance.

ULTEM® has a unique combination of high performance in thermal, chemical, mechanical, and electrical properties. Typically only found in higher-cost engineered plastic manifold applications, this plastic provides higher performance for fluidic manifolds than polycarbonate, polysulfone, and acrylic manifolds. As ULTEM features higher working temperatures and superior chemical resistance, many consider this plastic a "powerhouse" due to these qualities. As a result, a broad cross-section of manufacturing industries use this type of plastic including medical, pharmaceutical, electronics, semiconductor design, automotive, and aerospace.

Radel®

For rapid prototyping and manufacturing, Radel® (or polyphenyl sulfone (PPSU)) plastic resin is a tough and stable performer. Medical devices often use Radel® due to its stability and resistance to damage from repeated sterilizations. It can take steam, cold, radiation, and dry heat sterilization methods without stress-cracking after post production polishing, responding well to vapor polishing and optical machining. In its natural state, polished Radel® is dark amber, similar to ULTEM® and PES.

Acrylic

3 layered acrylic manifoldWith low cost and excellent clarity, acrylic is the most commonly used material for bonded device manifolds. It allows for a full inspection of all channels and passages and can be easily machined and bonded into assemblies. An expert machinist can drill holes in acrylic straight and clear.

Flame polishing, buffing, and optical machining are effective polishing processes. Manufacturers often produce highly polished acrylic lenses by optical machining. As acrylic is the closest plastic substitute for window glass, general purpose-grade cast and polished acrylic parts will block UV wavelengths up to 360 NM. For specific applications requiring transmittance of 280 NM and above, we suggest considering UVT grade.

In addition, acrylic has good weathering ability and dimensional stability. Due to these mechanical properties, it also performs well in pneumatic and vacuum applications and can support operating pressures as high as 150 psi.

COC & COP

COC and COP provide many benefits compared to traditional amorphous plastics used in fluidic manifolds, such as acrylic, ULTEM®, and polycarbonate. Best in class for transparency and light transmission, both COC and COP are suitable for optical applications. Industries like microfluidics and life sciences often use this plastic since they offer bio-compatibility and superior chemical resistance to chemicals classified as acids, alkalis, and/or hydrolysis — to name a few. They both also retain their properties to near glass temperature, not losing much structural integrity despite intense heat and/or pressure.

Polycarbonate

Clear layered bonded manifold made from polycarbonatePolycarbonate bonded manifolds are quickly replacing acrylic as a baseline material. As a highly versatile and tough plastic, this material is easy to machine, polish, weld, and bond. Polycarbonate also supports higher temperatures and has better chemical resistance than acrylic. In addition, this transparent material offers high modules of elasticity without compromising its strength or structure.

This materials also grants the product the opportunity to configure themselves as multilayer laminated manifolds. Experts tend to design manifolds with either D-shaped or full round channels rather than square ones with this distinct configuration. Channel spacing can be as close as 0.040 to the nearest feature size. The surface finish for valve mounting can be as good as 20 µin.

When bonded, polycarbonate provides a visually clear manifold. For pumps or valves with frequent assembly and disassembly, consider heat-staked threaded inserts over direct machined threads or helicoils since polycarbonate is stress sensitive to long-term loading in stress risers. Pullout strength and low stress on components make inserts the best choice for manifold design.

Polyvinyl Chloride (PVC)

Lightweight, durable, and easy to process, PVC (Polyvinyl Chloride) is one of the most popular thermoplastic polymers in the world. As PVC is a cost efficient and versatile material, it holds a wide variety of applications within several and often differing industries. Those include healthcare, electronics, automobile manufacturing, packaging, and other sectors. Capable of performing up to 60ºC (140ºF), PVC offers resistance to mild acids, alkalis, and solvents.

Research has also demonstrated that PVC effectively protects the environment in terms of low greenhouse gas emissions and conservation of energy.

Polysulfone

polysulfone fluidic manifoldSuitable for hot water applications, polysulfone has a high continuous service temperature of 148ºC (~300°F). Additionally, it resists water absorption and can tolerate steam sterilization up to 140.5ºC (~285°F). FDA-compliant devices often contain clear polysulfone components.

Double-sided full round or single-sided D-channel manifold designs are feasible. Full round bonded channels give the best flow and the least opportunity for unswept volume, although machining two sides do increase costs. The typical minimal channel size for polysulfone is 0.020 (.5 mm) with preferred channel spacing 0.040 apart.

Unlimited layers are theoretically possible with polysulfone, but costs rise with layer count. Multiple two-layer manifolds are a smarter choice in practice than a single large, highly complex, multi-layered manifold. General performance is higher with polysulfone than with acrylic and polycarbonate, but it is more expensive as a raw material. Staked-in threaded inserts are recommended over helicoils to avoid stress-cracking concerns.

Trying to select a plastic for your bonded manifold needs? Take our Resin Selector Quiz now!