5 Checks Every Engineer Should Run Before Approving Silicone Materials

Here’s a scenario I’ve lived through more times than I care to count. You get a drum of dow corning elastomeric coatings or a tube of dow corning vacuum lubricant for a critical job. The spec sheet looks fine. The price is right. The vendor has been okay before.

Then, six weeks later, the coating peels off in sheets. Or the lubricant gums up inside the valve. And suddenly you’re looking at a $22,000 redo—and a delayed product launch.

I’m a quality compliance manager in the chemical supply space. I review roughly 200 unique material deliveries every year. And in Q1 2024, I rejected 11% of first deliveries because the product didn’t match the specifications we agreed on. Not because the vendor was malicious—but because nobody ran the right checks before signing off.

This checklist is built around those specific failures. If you’re specifying materials for vertical powder coating, custom gun coatings, or any silicon-based industrial material, run through these five checks before you approve the delivery.

Who this checklist is for

This is for engineers and procurement leads who are tired of being surprised by material failures. It’s for people who want a repeatable process instead of relying on memory or trust. If you’ve ever had a batch fail in the field and wished you had caught it earlier, this is for you.

There are five steps. Each one takes about 10 minutes for a standard material order. That’s 50 minutes total to potentially save weeks of rework.

Step 1: Verify the exact chemistry against your application

This seems obvious, but I see it skipped all the time. You ordered a dow corning elastomeric coating for high-temperature electronics. The delivery says “Dow Corning Elastomeric Coating.” Looks right, right?

Check the full part number. There are at least four different grades of high-temp elastomeric coatings from Dow Corning—each formulated for a different upper temperature limit and substrate. The difference between grade A and grade B could be 50°C of thermal tolerance.

What to do: Pull the material safety data sheet (MSDS) or technical data sheet (TDS) from the manufacturer’s website. Compare the listed chemical properties (viscosity, solids content, cure schedule) against what your application actually needs. If there’s a mismatch, reject the material before it hits the floor.

Step 2: Run a simple viscosity check on arrival

Here’s something vendors won’t tell you: viscosity shifts are the most common hidden defect I see. A batch of dow corning vacuum lubricant that’s even 10% thicker than your spec will cause drag in precision valves. A coating that’s too thin won’t cover corners properly.

Most companies don’t test viscosity on arrival. They assume the vendor’s batch certificate is accurate. I learned that lesson the hard way after a batch of custom lubricant seized a rotary valve. The certification said 12,000 cP. The actual material was 16,000 cP.

What to do: Get a simple rotational viscometer (they cost around $300). Test one sample from each container on a standard schedule. Compare against the spec range listed on the TDS. If it’s outside tolerance, don’t accept it.

I’ll admit this step isn’t always necessary—I usually skip it for small batches under 5 gallons. But for any production run of $500+ in material cost, it’s non-negotiable.

Step 3: Check cure time under your actual conditions

This is the step most engineers forget. The TDS lists cure time at 72°F and 50% humidity. But your vertical powder coating line runs at 85°F with forced airflow. Or your custom gun coatings are applied in a humid environment.

The difference can be dramatic. A coating that cures in 24 hours in the lab might take 72 hours on your factory floor. And if you move parts to storage before the coating is fully set, you get smudging, dust adhesion, or delamination.

What to do: Before you approve the batch, apply a small sample—maybe six coupons—and cure them under your actual conditions. Check hardness at 24, 48, and 72 hours using a simple Shore A durometer test. If the material isn’t reaching spec by the deadline you need, you need to adjust your process or the material.

Step 4: Verify packaging integrity

I know this sounds basic. But I rejected three drums in Q1 2024 because the seal had been broken during shipping. The material had been exposed to moisture for 11 days in transit. That’s plenty of time for silicone-based materials—especially moisture-cure types—to start reacting inside the container.

The drum looked fine from the outside. The tamper-evident seal was intact. But when I opened it, there was a crust of cured material around the lid lip. That was the telltale sign.

What to do: For every container, check the seal visually. Weigh the drum and compare against the expected weight. A significant weight difference could mean leakage or contamination. Document the condition with a photo on your phone. This takes two minutes per container.

Step 5: Get a simple adhesion test done (the 90-degree peel test)

This is the single most valuable test I’ve added to our process. It’s not a replacement for full mechanical testing. But it catches more failures than any other single check.

The 90-degree peel test: Apply your coating or adhesive to a representative substrate (same material, same surface prep). Cure it according to spec. Then use a utility knife to make a 1-inch wide strip. Peel it back at 90 degrees—by hand, or with a pull-tester if you have one—and observe the failure mode.

• Adhesive failure: The material comes clean off the surface. That’s a bad bond—likely contamination or wrong surface prep.
• Cohesive failure: The material tears within itself, leaving residue on both surfaces. That’s an acceptable bond (the material was stronger than the interface).
• Mixed failure: Spotty. Indicates inconsistent cleaning or application.

If you see adhesive failure on the first sample, reject the batch. It’s almost always a sign of improper storage or surface contamination at the vendor level.

Common mistakes to avoid

• Don’t rely on the vendor’s certificate of analysis alone. It measures the sample they sent—not the batch you received. If there’s a discrepancy, it’s your problem, not theirs.
• Don’t skip the cure check for “standard” products. Things like dow corning vacuum lubricant seem straightforward, but curing behavior changes with temperature and humidity. Test under your conditions.
• Don’t assume “dow corning” is the only option. If you’re looking at what are considered to be among the earliest adhesives, you might be comparing natural vs. synthetic. Make sure your material matches your application—not just the brand name.

The 12-point checklist I created after my third mistake like this has saved us an estimated $8,000 in potential rework just this year. Five checks, 50 minutes, and a lot of failed experiments later—I don’t trust vendor certifications alone anymore. Neither should you.