Fluid handling
by Sara McCaslin Sara McCaslin No Comments

Kynar (PVDF) vs. PTFE: Choosing the Right Fluoropolymer for Fluid Handling Seals


A specification that simply calls out “flouropolymer” is quite incomplete. PVDF and PTFE are both fluoropolymers and grouped under that umbrella term, but they are quite different. When it comes to mechanical and chemical behavior, specifying the wrong material can lead to premature seal failure and expensive downtime. The objective of this blog post is to provide a clear, practical basis for determining which material is the most appropriate.

How PVDF and PTFE Are the Same

Both PVDF (Kynar) and PTFE (Teflon) resist a broad range of acids and solvents, and both handle highly elevated temperatures better than elastomers. They also share low coefficients of friction, low surface adhesion, and non-stick properties. And both have their own specialties in fluid-handling applications.

Where PVDF Pulls Ahead of PTFE 

PVDF (Polyvinylidene Fluoride) has distinct advantages over PTFE (Polytetrafluoroethylene). It exhibits better mechanical strength than PTFE (by about 2-3x) and has excellent abrasion resistance, which means it can hold up better under slurry or particulate-laden fluid flow. Wear resistance is another property of PVDF that excels over PTFE, especially in dynamic seal contact, such as wear sleeves and piston rings.  It also exhibits lower cold flow and creep under compression, which is very important for seal performance over time under sustained load. 

Finally, PTFE might be more expensive than the equivalent PVDF stock. While PTFE stock is inexpensive, PVDF is melt-processable. Being melt-processable can make PVDF vastly more cost-effective for high-volume molded parts.

Where PVDF Loses Against PTFE

PTFE has an extremely low coefficient of friction compared to PVDF (0.04-0.10 vs. 0.15-0.30). And in the presence of high-pH caustics and strong bases, PTFE performs without issue, whereas PVDF begins to degrade. There are also polar solvents, amines, fuming acids, and some ketones that attack PVDF’s chemical structure and polymer chain. PVDF’s chemical resistance chart has real gaps where PTFE’s is closer to “resistant to everything below its temp limit.” Always check material compatibility at your actual operating temperature, not ambient temperature. It is a fact that many “resistant” ratings degrade at elevated temperatures.

PVDF vs PTFE – Who Wins?

The table below summarizes the similarities and differences between PVDF and PTFE.

*Values are approximate; exact values are based on material grade and blend

* PVDF: Lower for high-volume molding; PTFE: Lower for machined stock

Decision framework

Here is a checklist for fluid handling engineers choosing between PVDF and PTFE:

  1. What’s touching the seal? Check for a strong base or problem solvent first; if it is present, PTFE wins outright
  2. Is there abrasive/particulate content or high dynamic wear? If so, lean toward PVDF if  the compatibility allows
  3. Is the seal under sustained compressive load where creep matters? If so, lean toward PVDF
  4. Static seal, clean chemistry, wide chemical exposure risk (multi-product lines, CIP/COP)? PTFE is the safer default.

The figures below show examples of where each material performs best.

Conclusion

Borderline cases with mixed process streams, elevated-temperature caustics, or unusual solvent blends are exactly where a materials engineer should get involved before committing to tooling. It is always cheaper to change a decision on paper than after seals are cut. Advanced EMC is here to help you choose the right material and seal for your fluid-handling challenges. And keep in mind that Advanced EMC offers several material options if neither material is a fit.

Semiconductor
by Daniel Mays Daniel Mays No Comments

Meeting SEMI Standards for Seal Purity, Outgassing, and Chemical Resistance

Semiconductor fabrication facilities are among the most demanding environments for seal materials on the planet because a single contamination event can scrap a wafer batch worth hundreds of thousands of dollars. And every polymer, lubricant, and elastomeric material contains residual volatiles. SEMI standards deal with how to take these residual volatiles into account when designing components, such as seals, for wafer fabrication environments. The purpose of this blog post is to discuss what SEMI standards actually require and how engineers select bearings to meet them.

The SEMI Standards Landscape

SEMI standards serve as the common language of the global semiconductor supply chain. For example, SEMI standards define fitness for use by establishing minimum thresholds (e.g., outgassing limits, contamination levels, chemical compatibility requirements) that a component must meet to be considered safe for use in semiconductor manufacturing environments. These standards also protect the wafer from contamination that can destroy device yield and make suppliers accountable. 

By referencing a SEMI standard in a procurement specification, a fabrication engineer can require documented, third-party-verifiable compliance rather than relying on a supplier’s marketing claims. These standards also enable global interoperability: tools, chemicals, and components built to SEMI standards can move across fabrications and geographies without extensive re-qualification. This serves as a major economic benefit in a highly globalized industry.

SEMI F-Series (Facilities and Materials)

The SEMI F-series serves as the most relevant category for seals. Standards like SEMI F57 govern polymeric components and wetted surface materials used in UHP (ultra-high purity) gas distribution systems, covering surface finish requirements, material qualification, and cleanliness protocols. SEMI F2 addresses test methods for metallic contamination on wetted surfaces. These are the specs a seal or bearing supplier is most likely to be asked to demonstrate compliance with.

SEMI C-Series (Chemicals)

The SEMI C-Series of standards defines purity grades and acceptable contamination levels for process chemicals such as acids, solvents, and oxidizers. While these standards primarily govern the chemicals themselves, they are also critically important for material selection. If your seal is sitting in a bath governed by a C-series chemical specification, that specification indirectly defines the chemical resistance your seal must demonstrate. Engineers selecting materials for wetted components need to understand what chemical grade they are designing for.

SEMI S2 (Safety Guidelines for Semiconductor Manufacturing Equipment)

S2 is a broad equipment safety standard with direct implications for materials selection. It addresses chemical containment, materials of construction for chemical-wetted components, ventilation requirements, and labeling. It’s often the standard a tool OEM must satisfy as a condition of fab entry, making it a gateway document that touches bearing and seal design.

Purity: Metallic Contamination and Ionic Cleanliness

When it comes to cleanliness in fabrication environments, the core concern when it comes to contamination is the presence of trace metals (Fe, Na, K, Ca) as killer defects in semiconductor devices. Both dynamic seals are going to shed particles, and this includes wear debris, surface oxides, and manufacturing residues. Among the key material considerations are the use of PTFE bearings and seals, while other options include ceramic bearings (Si₃N₄, ZrO₂) as the go-to for ultra-pure applications and surface treatments (e.g., electropolishing, passivation, and their limits).

Outgassing: The Invisible Contamination Problem

Through outgassing, volatile organic compounds (VOCs) deposit on wafer surfaces and disrupt lithography, deposition, and etch processes. Two standards commonly apply: SEMI F10 and NASA ASTM E595, serving as the benchmarks engineers reference. And there are two key metrics that matter: ML (Total Mass Loss) and CVCM (Collected Volatile Condensable Materials). The general targets used by engineers are TML < 1.0% and CVCM < 0.1%. And remember that a material can pass TML and fail CVCM. Bearings and seals must comply with both. However, CVCM is the one that matters most because it captures what actually re-deposits on a cooler surface.

In seal assemblies, the vast majority of problems come from lubricants and greases (silicone-based greases are particularly problematic in vacuum) and adhesives, polymer cage materials, and elastomeric seals. This includes nylon and acetal bearing cages and standard elastomeric seals with curative that can volatize under heat and vacuum. To avoid these issues, industry best practice is to use …

  • PFPE-based dry film lubricants
  • PTFE lip seals (which are known for their high purity and self-lubrication)
  • Perfluoroelastomers (FFKM)

Bake-Out Procedures

As already discussed, every polymer, lubricant, and elastomeric material contains residual volatiles that may include trapped solvents from manufacturing, absorbed moisture, unreacted monomers, and plasticizer fractions. At room temperature, these substances release slowly over weeks or months. Elevated temperature, however, drives that same process in hours, forcing the material to shed its residual volatiles before it is ever installed. This process is known as bake-out and must be accomplished for a material to be safe to use in a high-purity environment.

Chemical Resistance: Surviving the Process Chemistry

The process chemistry involved with semiconductor manufacturers includes chemicals such as HF, H₂SO₄, HCl, H₂O₂, IPA, NMP, ozone, and aggressive plasma environments. And although a material may be listed as chemically resistant on a data sheet, that does not account for critical variables such as concentration, temperature, and exposure time. Swell, extraction, and stress cracking are the failure modes that tables consistently miss.

The material compatibility hierarchy for seals is:

  • FFKM (Kalrez®, Perlast®): broadest chemical resistance, low extractables
  • PTFE: excellent passive resistance but poor dynamic sealing performance
  • EPDM / FKM (Viton®): acceptable in some applications, disqualified in others (HF is a hard no for FKM)

Conclusion

SEMI compliance is not just a checklist, but rather a systems-level engineering discipline. Material selection, outgassing qualification, and chemical resistance validation must work together to result in a fully SEMI-compliant seal. Engineers who treat these as a system rather than separate line items build better products. If you are looking for a SEMI-compliant sealing solution, contact the engineers at Advanced EMC today.