When developing custom sealing parts, confirming the material before manufacturing is one of the most critical steps. Different materials—whether NBR, FKM, EPDM, PTFE, PEEK, or PU—have unique molding behaviors, shrinkage rates, hardness levels, and performance characteristics.
Skipping this step can lead to serious engineering and production risks, affecting everything from manufacturing cost to the service life of the final product.

As a professional sealing manufacturer, DXTSEALS outlines the major risks of failing to confirm the material before mold design and production.

1️⃣ Incorrect Material Shrinkage Leads to Dimensional Errors

Every material has its own shrinkage rate, and mold dimensions must be calculated accordingly.

If the material is not confirmed before mold machining, the following issues can occur:

• Finished parts do not match the drawing

• Outer diameter or inner diameter out of tolerance

• Excessive flash or uneven surface

• Seal cannot be installed or fails to fit the groove

• Mold must be reworked or remade

For example:

• NBR shrinkage ≈ 1.5%

• FKM shrinkage ≈ 2.0%

• EPDM shrinkage ≈ 1.6%

• PU shrinkage ≈ 1.2–1.3%

• PTFE shrinkage ≈ 3–5%

👉 Even a 0.2% difference can cause dimensional failure in precision sealing components.

2️⃣ Wrong Hardness or Elasticity Causes Poor Sealing Performance

Material hardness directly affects sealing:

• Too soft → deformation, extrusion, leakage

• Too hard → insufficient compression, weak sealing force

• Wrong elasticity → failure under dynamic movement

If hardness is selected after molding, the mold cavity may no longer match the compression ratio needed for proper sealing.

3️⃣ Molding Defects Increase Scrap Rate and Production Cost

Different materials have different:

• curing temperatures

• curing times

• flow characteristics

• mold release behavior

• filling capability

Using the wrong material can result in:

• air bubbles

• incomplete filling

• edge distortion

• scorching or under-curing

• uneven surface finish

These defects increase scrap rate and may require adjusting mold temperature, pressure, or even redesigning the mold.

4️⃣ Incompatible Materials Cause Chemical Swelling or Cracking

Selecting the wrong rubber or polymer can lead to premature failure when in contact with:

• oils

• fuels

• refrigerants

• acids or bases

• hydraulic fluids

• steam or hot water

Typical examples:

• EPDM fails in oil → swelling and cracking

• NBR fails in ozone → aging and surface cracks

• PU fails in hot water → hydrolysis

• Silicone fails in dynamic friction → tearing

👉 Without confirming the actual working medium, the sealing life may be reduced from 2 years to 2 weeks.

5️⃣ Thermal Mismatch Causes Hardening or Deformation

Materials have different temperature limits:

• NBR: –40°C to 120°C

• FKM: –20°C to 200°C

• EPDM: –50°C to 150°C

• Silicone: –60°C to 200°C

• PTFE: –70°C to 260°C

• PU: –30°C to 90°C

Using a material outside its temperature range can cause:

• loss of elasticity

• cracking

• hardening

• extrusion

• dimensional distortion

👉 Without confirming the operating temperature, the seal may fail instantly.

6️⃣ Potential Mold Damage Due to Incompatible Process Parameters

Rubber molding requires specific:

• pressure

• temperature

• curing time

If material is not planned beforehand:

• overheating may damage mold surfaces

• incorrect pressure may deform the mold cavity

• slow-curing materials increase production time and costs

Mold longevity and stability depend on proper material planning.

7️⃣ Increased Lead Time and Project Delays

Changing material mid-way often means:

• redesigning the mold

• recalculating shrinkage

• adjusting hardness

• new sampling

• longer testing cycles

This can delay the entire project—sometimes by weeks or months.

8️⃣ Reduced Seal Lifespan and Higher Failure Rate

The final and most significant impact is on the service life of the seal.

Wrong material selection may cause:

• leakage

• poor wear resistance

• compression set

• thermal degradation

• chemical attack

• dynamic friction failure

A custom seal designed with the correct material can last 3–10 times longer than one made with the wrong material.

⭐ Conclusion: Confirming Material First Is Essential for Successful Seal Customization

Failing to confirm material before molding introduces risks across every stage:

✔ mold accuracy
✔ molding quality
✔ sealing performance
✔ chemical and thermal compatibility
✔ lifespan and reliability
✔ total project cost

To ensure stability and cost control, material confirmation must be the first step in custom seal development.

DXTSEALS provides expert support on:

• material recommendation

• working condition analysis

• mold design optimization

• prototype sampling

• performance testing

Ensuring that every custom sealing solution meets the exact requirements of your application.