PFAS-Free Liquid Cooling Hardware for AI Data Centers

Fluorine-free polymers are redefining liquid cooling hardware, delivering chemical stability and dielectric strength without relying on PFAS.

Artificial intelligence workloads push rack power densities beyond 80–100 kW. Air cooling cannot manage that thermal load without extreme airflow and acoustic penalties. Direct liquid cooling and cold-plate technology now dominate high-performance clusters. Yet, most current systems rely on per- and polyfluoroalkyl substances (PFAS) in tubing, manifolds, gaskets, and coatings because fluoropolymers provide low surface energy, high dielectric strength, and stability in glycol- or dielectric-based coolants. Global restrictions on PFAS are accelerating the need for fluorine-free polymers that maintain thermal, chemical, and mechanical integrity within closed coolant loops.

You can also read: Thermally Conductive Plastic for Cooling Electronics.

Performance Requirements for PFAS-Free Polymers

Liquid cooling hardware faces constant flow, sustained clamp load, temperatures around 60–85 °C, and repeated power-driven thermal spikes. Polymers inside the loop must withstand ethylene/propylene glycol blends, synthetic esters, mineral oils, or engineered dielectric fluids without leaching ions, plasticizers, or oligomers into the circuit. Dimensional creep under bolt compression, permeation of dissolved gases, and hydrolysis can cause premature failure of seals and manifolds. PFAS-free materials need high dielectric breakdown strength to avoid arcing in cold plates mounted above processors and uniform thermal expansion to prevent distortion in copper or aluminum heat exchangers.

Alternatives for Manifolds and Tubing

Several high-performance thermoplastics now replace PVDF, PTFE-lined steel pipes, or FEP hoses. Polyphenylsulfone (PPSU) maintains stiffness and hydrolysis resistance up to 90 °C, tolerates glycol-based fluids, and offers better notch toughness than PSU or PES. Polyether ether ketone (PEEK) resists continuous exposure to 120 °C liquids, carries high pressure without stress cracking, and retains tensile strength above 100 MPa. Polyetherimide (PEI) and liquid crystal polymers (LCPs) provide dimensional stability for precision manifolds with microchannel geometries. Glass-fiber reinforcement increases modulus but needs surface treatments to avoid fiber-print defects in weld zones.

Extruded PEX and high-temperature polyamides (PA 6T/66 blends) serve in low-pressure segments. They need oxygen scavengers in the coolant because polyamides embrittle in oxidative environments. Twin-screw extruders compound stabilizers, impact modifiers, and processing aids to achieve consistent viscosity during pipe or hose fabrication.

Elastomeric Seals Without PTFE or FFKM

Fluoroelastomer O-rings (FKM, FFKM) dominate liquid cooling seals. PFAS-free options now center on peroxide-cured EPDM, hydrogenated nitrile rubber (HNBR), and silicone rubber. Peroxide-cured EPDM withstands 100 °C water-glycol blends, resists steam intrusion, and holds compression set values under 30 % after 1 000 hours at 125 °C. HNBR tolerates oils and synthetic esters but requires stabilizers to avoid oxidative cracking. Silicone rubber manages wide thermal ranges but suffers high gas permeability; designers increase gland squeeze and surface micro-texturing to improve sealing force without PTFE back-up rings. Thermoplastic vulcanizates (TPE-V) offer recyclable alternatives; they suit quick-connect fittings but deform under long-term clamp load above 80 °C.

Coolant Compatibility and Failure Modes

PFAS-free hardware must function with three cooling families: water-glycol, dielectric hydrocarbons (synthetic esters, PAO), and fluoroketones. Glycols reduce surface tension but accelerate oxidation of some elastomers and extract plasticizers from lower-modulus polymers. Dielectric oils attack certain polyesters; materials like PEEK and PPSU show minimal swelling. Ion leaching from fillers or pigments can raise coolant conductivity, which increases electrochemical corrosion inside microchannels. Operators track pH, conductivity, metal ion content, and total organic carbon to validate material compatibility. Typical failure modes include stress cracking in low-crystallinity resins, seal extrusion under pressure pulsation, creep deformation in manifold flanges, and particulate shedding that clogs cold-plate fins.

Testing and Validation

Manufacturers subject candidate materials to UL 746C thermal aging tests, ASME liquid cooling loop pressure cycling, and ISO 16750 thermal shock profiles. ASTM D471 verifies volumetric swelling in candidate coolants, while ISO 815 measures compression set in seals after thermal exposure. Test loops circulate coolant at flow rates of 10–20 L/min and monitor pressure drop, dissolved oxygen, and particle counts. Manifolds bonded to copper cold plates undergo thermal cycling between 20 °C and 80 °C to simulate processor load swings. Engineers measure bolt load retention with extensometers and monitor microleakage using helium mass spectrometry. Failure criteria include loss of sealing force, torque relaxation above 15 %, coolant permeation greater than 1 g/m²·day, or discoloration indicating polymer oxidation.

Manufacturing Considerations

Injection molding and extrusion remain viable for PFAS-free hardware. Melt temperatures for PPSU and PEI exceed 350 °C; molds require high venting and corrosion-resistant steel to handle acidic off-gassing. PEEK cold plates need stringent control of moisture and residence time; otherwise, chain scission compromises strength. Surface treatments—plasma activation, UV-ozone, or thin sol–gel coatings—increase adhesion between polymer manifolds and metal inserts. Laser welding and infrared welding enable leak-tight joints without adhesives or fluorinated sealants. Precision machining requires PCD or diamond tooling to prevent smearing of semicrystalline polymers across microchannels.

PFAS-free AI Data Centers Outlook

PFAS-free cooling hardware for AI data centers now shifts from trial installations to early production. PEEK, PPSU, and PEI manifolds already operate in single-phase immersion testbeds. EPDM, HNBR, and silicone seals achieve leakage rates comparable to FKMs when designed with proper gland geometry and coolant chemistry control. Remaining challenges include improving thermal conductivity, ensuring creep resistance over five-year lifetimes, and building recyclability into end-of-life management of polymer-metal assemblies. As rack power densities rise, polymer selection, flow design, and seal integrity will determine whether PFAS-free systems meet both regulatory mandates and uptime demands in next-generation AI compute infrastructure.