Who Is This Checklist For?
If you’re specifying materials for hoses, seals, gaskets, or tubing—especially if you’re trying to decide between silicone and thermoplastic polyurethane (TPU)—this is for you.
I’m a quality and brand compliance manager at a rubber and plastics company. I review roughly 200 unique items per year before they go to customers. Over time, I’ve seen the same confusion pop up again and again: When is silicone the obvious choice? When is TPU better? And where do people get it wrong?
This checklist is broken into 5 steps. It’s designed to give you a clear, repeatable process so you don’t end up with a $22,000 redo like the guy who specified silicone for a hose exposed to a specific hydraulic oil. (We’ll get to that.)
Step 1: Start With Your Operating Temperature
This is the first filter, not the final answer. But if you miss this, nothing else matters.
Ask: What’s the continuous operating temperature range your part will see?
- Silicone: Handles -60°C to 230°C continuously (-76°F to 446°F). Some formulations go higher. It’s exceptional in high-heat environments like oven gaskets or engine bay components.
- TPU: Typically -40°C to 80°C (-40°F to 176°F) for standard grades. Some high-performance TPU grades can handle up to 120°C (248°F), but that’s the ceiling.
Here’s a mistake I see in our Q1 2024 quality audit: people assume TPU can handle the same broad temperature range as silicone because they confuse “thermoplastic” with “high temp.” It’s not the same. TPU is a thermoplastic elastomer; silicone is a thermoset rubber. They behave very differently under heat.
Checkpoint: If your application is above 100°C sustained, you’re probably looking at silicone. If it’s below 80°C, both are candidates.
Step 2: Check Chemical Compatibility (The One That Often Gets Overlooked)
Most buyers focus on temperature and price and completely miss chemical resistance until it’s too late.
Ask: What fluids, oils, solvents, or chemicals will this part contact?
Here’s the thing vendors won’t tell you upfront: silicone and TPU have wildly different chemistries.
- Silicone: Excellent resistance to water, steam, and UV. Poor resistance to hydrocarbons (oils, gasoline, solvents) and many acids/alkalis. Silicone swells in oils. I rejected a batch of 400 silicone gaskets last year because the customer was testing them against a standard hydraulic oil—they had the wrong material entirely.
- TPU: Excellent resistance to oils, greases, fuels, and many solvents. Lower resistance to strong acids, bases, and hot water/steam.
Checkpoint: If your part touches oil or fuel, TPU is almost always the safer bet. If it touches hot water or steam, silicone wins.
Step 3: Consider Mechanical Demands (Tear, Abrasion, Flex)
This is where the material choice can really differentiate performance. If the part needs to flex repeatedly, resist tearing, or survive abrasion, pay close attention.
- Silicone: Lower tensile strength and tear resistance. It’s flexible, but not tough. It can tear if stretched over sharp edges. Great for static seals or gaskets in controlled environments.
- TPU: High tensile strength, excellent abrasion resistance, and good tear strength. It's the go-to for dynamic applications like hydraulic hoses, pneumatic tubing, or moving seals.
I once watched a colleague approve a TPU tube for a robotic arm application that needed constant flexing. The TPU tube lasted 18 months. The previous silicone tube lasted 6 weeks. The cost difference was about 15%. That’s a classic case of spending smarter, not just cheaper.
Checkpoint: If it bends, moves, or drags against something, TPU is usually right. If it sits still, silicone might be fine.
Step 4: Evaluate Your Cost Tolerance (Beyond Unit Price)
The question everyone asks: “Which is cheaper?” The question they should ask: “What’s the total cost of ownership?”
Here’s a rough pricing guide based on publicly available data (2025 pricing, actual costs will vary—always verify):
Silicone (per kg): $8–$25 depending on grade and hardness. Higher cost for high-purity or food-grade versions.
TPU (per kg): $4–$12 for standard grades. Specialty TPUs (flame retardant, hydrolysis-resistant) can go higher.
But raw material cost isn’t everything. TPU can often be molded in faster cycle times (thermoplastic processing). Silicone requires curing, which adds time. If you’re running 50,000 units annually, a faster processing cycle with TPU might offset a higher per-unit material price.
Checkpoint: Don’t just compare material cost. Factor in processing time, tooling complexity, and expected lifespan.
Step 5: Check for Regulatory or Brand Requirements
This is the step I see beginners skip.
Ask: Does your industry or customer require specific certifications?
- Silicone: Widely used in FDA, USP Class VI, and food-contact applications. Good for medical and food processing equipment.
- TPU: Not typically used in high-temperature food contact. Many TPU grades are not FDA approved. However, TPU is common in automotive, hydraulic, and pneumatic systems.
If your output needs to be FDA-compliant, that choice is usually silicone. If your brand emphasizes oil resistance or durability in dynamic applications, TPU might be a better match for your brand story.
When I implemented our verification protocol in 2022, I noticed a pattern: clients who specified TPU for every part were over-engineering static sealing applications. And clients who specified silicone for every part were under-specifying for abrasive environments. The right choice depends on the specific application.
Common Mistakes to Avoid
- Assuming silicone is always the high-temperature option. It is, but if your application also involves oil—silicone will swell and fail.
- Choosing TPU just because it’s cheaper per kg. Processing cost and lifespan often change the math.
- Ignoring UV and weathering exposure. Silicone handles UV very well; many TPU grades degrade in sunlight unless stabilized.
- Not testing a prototype in actual conditions. I can’t tell you how many times a material looked perfect on paper but failed in the field. The defect ruined 8,000 units in storage conditions for one client because they didn’t account for humidity.
Final reminder: Checklist is great for process. But nothing replaces a real-world test. If you’re still unsure, ask a supplier to send a sample in both materials. Run your test. Check your spec sheet. Then decide.
Prices as of January 2025; verify current rates with suppliers.