Dongying (Suzhou Dongying Electronic Technology Co., Ltd.) is a mold maker and injection molder in Suzhou, China. For liquid-cooling projects we review drawings and requirements to see whether a part can be evaluated for molding, for example cold-plate fluid connectors. Every project starts with that review; nothing in this article is a performance claim for any part.
Which plastic parts appear in a liquid-cooled rack
Short answer: plastics show up both in wetted parts that touch coolant and in dry parts around the loop, and the two groups need different checks.
| Part type | Wetted? | Typical concern |
|---|---|---|
| Cold-plate fluid connectors and inlet/outlet fittings | Yes | Coolant compatibility, sealing face, burst and pressure behavior |
| Manifold fittings, adapters, tube ends | Yes | Long-term aging in coolant at operating temperature |
| Quick-connect internal parts (if plastic) | Yes | Wear, sealing, mating with metal bodies |
| Cold-plate covers, retainers, brackets | Usually no | Stiffness, flatness, screw bosses, flame requirement |
| Hose clips, cable and tube guides | No | Fit, routing, assembly force |
| Leak-sensor housings, insulating covers | No | Electrical insulation, flame requirement |
Separating the list this way keeps the material discussion focused: dry parts can often follow normal electronics housing practice, while wetted parts must be approved for the specific fluid.
Start from the wetted-material list
Short answer: the coolant specification and the system's wetted-material list decide which plastics are even allowed, so get that list before choosing a grade.
The Open Compute Project (OCP) guideline for propylene glycol-based fluids in single-phase cold-plate racks says that the materials touching the fluid are called wetted materials, that the data center operator shall certify compatibility of the fluid with all wetted components, and that any addition to the wetted-material list requires the fluid to be re-evaluated (OCP). Its table of acceptable non-metals names EPDM, Viton grades, FEP, PTFE, PP, HDPE and PEEK.
Two practical points follow:
- A common engineering plastic such as glass-filled PPS or PA66 may be technically reasonable, yet still need approval from the system owner and fluid supplier if it is not on the project's list.
- The same guideline gives typical closed-loop temperatures below 49 °C and says operation above 66 °C needs the wetted-material list reviewed again (OCP). Ask for the real maximum fluid temperature, not only the nominal one.
Coolant aging: why "it is a strong plastic" is not enough
Short answer: hot water and glycol slowly attack some polymers through hydrolysis, so long-term aging data in the actual fluid matters more than dry datasheet strength.
Glycol-water coolants are mild compared with many chemicals, but exposure lasts for years at elevated temperature. Polyamides are the classic example. A study of PA66-GF30 in ethylene glycol-water found that a hydrolysis-stabilized grade held up clearly better than a standard grade, but that the stabilizer lost effectiveness at higher temperatures and both grades degraded severely at the highest test temperature (Polymer International). Material suppliers therefore list coolant resistance grade by grade: Celanese's datasheet for a hydrolysis-resistant PA66-GF30 shows separate ratings for glycol-water and specific coolants at stated temperatures (CAMPUS).
| Question to ask | Why it matters |
|---|---|
| Which fluid exactly (water, PG25, other) and which inhibitor package? | Additives can change compatibility |
| Maximum and continuous fluid temperature? | Aging speeds up with temperature |
| Is there aging data for the exact grade in this fluid? | Family names hide large grade differences |
| What property is the pass criterion (strength, elongation, weight, dimensions)? | Defines the test before results arrive |
| Can the part be tested in the customer's loop or rig? | Lab immersion does not cover pressure cycles |
Solvay's Ryton PPS design guide lists hot water resistance as one of the main factors for choosing between its glass-reinforced grades, which shows that even within PPS the grade choice matters (Solvay).
Sealing faces, threads and leak paths
Short answer: most leak risk sits at sealing surfaces, threads and insert interfaces, so define these features and how they will be inspected before the mold is designed.
- O-ring grooves and sealing faces: gate marks, parting lines and weld lines should stay off them. Agree on a surface condition and an inspection method.
- Molded threads or metal inserts: decide whether a metal insert carries the thread or the seal, and who supplies it. Our insert molding inputs list what to send.
- Weld lines near pressure-loaded walls: the Ryton guide notes that weld lines in glass-filled PPS are resin-rich and weaker, and should be placed in low-load areas (Solvay). In a pressurized connector, that rule matters more than in a dry bracket.
- Particles: the OCP guideline recommends fine side-stream filtration and warns against thread sealants that can introduce particles into the fluid (OCP). Burrs, flash and loose fibers at internal passages deserve the same attention.
How a molder evaluates a liquid-cooling part
Short answer: the evaluation checks whether the geometry, material and test plan fit together, and it ends with a clear list of risks and open items, not a promise.
A typical review covers:
- Drawing and 3D model with revision, sealing features and datums.
- Approved or proposed material grades, and who approves additions to the wetted-material list.
- Wall thickness, flow length and gate options for the shortlisted grade, often checked with mold-flow analysis.
- Insert and thread concept, parting line and ejector positions away from sealing faces.
- The customer's validation plan: leak, pressure, aging and any flame tests, and who runs them.
- Delivery mode: whether the mold is handed over or kept at the molder with part supply; see tooling and supply scope.
The result is a feasibility view and a list of points the customer must confirm. Final suitability always rests on the customer's own qualification in the real system.
What to put in your RFQ
Short answer: send the fluid and temperature data together with the drawing, because a liquid-cooling part cannot be assessed from geometry alone.
- 3D model and drawing with revision; mark sealing faces, threads and critical datums.
- Fluid type, inhibitor package and maximum fluid temperature.
- The project's wetted-material list, or the grades already approved.
- Operating and test pressure, and the leak test method.
- Any flame rating for dry parts near electronics.
- Annual volume, expected mold life and preferred delivery mode.
Read how we handle drawings and revisions and inspection and approval, or send your drawing.
FAQ
What plastic parts are used in AI server liquid cooling?
Plastic parts in AI server liquid cooling include wetted parts such as cold-plate fluid connectors, manifold fittings, adapters and some quick-connect internals, plus dry parts such as cold-plate covers, brackets, tube guides and leak-sensor housings. Wetted parts must be compatible with the coolant and approved on the system's wetted-material list, while dry parts mainly need stiffness, fit and, near electronics, a suitable flame rating.
Is PPS suitable for liquid cooling connectors?
Glass-filled PPS is often considered for fluid connectors because it is stiff, absorbs little water and many grades are inherently flame resistant. Suitability still depends on the exact grade, the coolant, the temperature and the system owner's approval. The OCP propylene glycol guideline does not list PPS among its acceptable plastics, so adding it to a project's wetted-material list would need evaluation with the fluid supplier.
Can PA66 be used in contact with glycol coolant?
Some PA66 grades are made for coolant contact, such as hydrolysis-resistant grades used in automotive cooling systems. Research shows that standard PA66-GF30 degrades in hot glycol-water much faster than stabilized grades, and that higher temperature shortens life for both. For a server loop, confirm the specific grade's aging data in your fluid at your maximum temperature, and include it in your own validation.
What is a wetted-material list?
A wetted-material list is the set of materials allowed to touch the coolant in a liquid-cooling system, including metals, elastomers, plastics and sealants. In the OCP guideline for propylene glycol-based fluids, the data center operator certifies compatibility of the fluid with all wetted components, and adding a material requires the fluid to be re-evaluated. Ask for this list before selecting a plastic grade for any wetted part.
What causes leaks in molded liquid-cooling parts?
Leaks usually start at sealing faces, threads and insert interfaces. Gate marks, parting lines or weld lines on an O-ring face, a weak weld line in a pressurized wall, or poor bonding around a metal insert can all open a leak path. Material aging in hot coolant can make these weaknesses worse over time. Defining sealing features and their inspection before the mold is designed is the main way to reduce this risk.
What should I send to have a liquid-cooling part evaluated?
Send the 3D model and drawing with revision and marked sealing faces, the fluid type and inhibitor package, the maximum fluid temperature, the project's wetted-material list or approved grades, operating and test pressures, the leak test method, annual volume and expected mold life. Also say whether you want the mold handed over or kept at Dongying with part supply. With these inputs we can assess whether the part can be evaluated for molding.
Related pages
Sources
- Open Compute Project, Guidelines for Using Propylene Glycol-Based Heat Transfer Fluids in Single-Phase Cold Plate-Based Liquid Cooled Racks (wetted materials, acceptable plastics, operating temperature, filtration): https://www.opencompute.org/documents/guidelines-for-using-propylene-glycol-based-heat-transfer-fluids-in-single-phase-cold-plate-based-liquid-cooled-racks-final-pdf
- Open Compute Project, Cooling Environments project: https://www.opencompute.org/wiki/Cooling_Environments
- "Resistance of glass fibre reinforced polyamide 6.6 materials to automotive cooling fluids: an analytical method for lifetime prediction", Polymer International: https://doi.org/10.1002/pi.6323
- Celanese, Zytel 70G30HSLR BK099 datasheet on CAMPUS Plastics (chemical media resistance incl. glycol-water and coolant): https://www.campusplastics.com/campus/en/datasheet/Zytel%C2%AE+70G30HSLR+BK099/Celanese/163/6dbd4c37
- Solvay Specialty Polymers, Ryton PPS Design Guide (grade selection incl. hot water resistance, weld lines; PDF hosted by Drake Plastics): https://drakeplastics.com/wp-content/uploads/2020/01/Ryton-PPS-Design-Guide.pdf