How to Choose Rotary Seal Materials for Chemical Exposure

Selecting Seal Materials for Aggressive Chemical Media

Understanding the challenge of rotary seals for chemical industry

Rotary seals in the chemical industry must operate in environments that combine aggressive fluids (acids, bases, solvents), wide temperature swings, variable pressure and shaft speeds, and mechanical wear. Choosing the wrong material leads to rapid swelling, hardening, cracking, increased leakage, unplanned downtime and high life-cycle costs. This article explains how to evaluate service conditions, compares common seal materials, and lays out a step-by-step selection and verification process to specify reliable rotary seals for chemical exposure.

Key service parameters to define before selecting rotary seals for chemical industry

Before comparing materials, collect precise operating data. Each parameter changes material suitability:

• Fluid identification: exact chemical(s), concentration, presence of mixed solvents, impurities or particulates.
• Temperature range: continuous, intermittent, and peak temperatures.
• Pressure: system static pressure and dynamic pressure spikes.
• Rotational speed and surface finish: shaft rpm and microfinishing (Ra) influence friction and wear.
• Motion type: pure rotary, oscillating, or combined rotary/reciprocating.
• Environment: external exposure to UV, ozone or cleaning agents.
• Size and geometry: gland dimensions, compression and extrusion gaps.

Documenting these variables allows engineers to match material properties to real service demands rather than relying on generic recommendations.

How chemical compatibility controls material selection for rotary seals for chemical industry

C hemical compatibility is the primary filter. Compatibility charts give an initial indication, but they are conservative and general; actual behavior depends on concentration, temperature and exposure time. Two main chemical failure modes are:

• Swell and softening — elastic rubbers (NBR, EPDM, FKM) often absorb solvents causing dimensional change, loss of sealing force and extrusion.
• Hardening and cracking — oxidative attack or crosslink scission (especially in non-fluorinated rubbers) leads to embrittlement and leakage.

Perfluoroelastomers (FFKM) and PTFE-based compounds show the broadest chemical resistance; elastomers like NBR and EPDM are economical but limited to specific chemistries (hydrocarbons or strong polar/water-based media respectively).

Temperature, pressure and mechanical considerations for rotary seals for chemical industry

Material selection must balance chemical resistance with thermal and mechanical performance:

• Temperature: PTFE and filled PTFE tolerate very high temperatures (typically up to 260–300°C depending on filler), FFKM typically up to 300°C, FKM up to ~200°C, NBR to ~100–120°C, EPDM to ~150°C, and silicone to ~200°C. Mechanical properties (compression set, modulus) change with temperature, impacting sealing reliability.
• Pressure and extrusion: soft materials swell under pressure; back-up rings (PTFE, PEEK) or harder-filled materials reduce extrusion risk in high-pressure rotary systems.
• Dynamic friction and wear: PTFE-based materials have low friction but require spring energizing or specific profiles for rotary motion; elastomers provide better resilience and sealing preload but can wear faster in abrasive or highly solvent-rich environments.

Material-by-material comparison for rotary seals for chemical industry

Below is a concise comparison of commonly used materials. Use it as a starting point; always confirm with supplier datasheets and compatibility tests under real conditions.

Table sources and typical ranges are summarized in the references at the end. Note that filled PTFE grades trade lower wear for higher rigidity; selection of filler depends on friction and wear priorities.

Design and operational tactics to extend seal life in chemical exposure

Material choice alone is not enough. Apply these design tactics to improve performance of rotary seals for chemical industry:

• Spring energizing and proper energizer choice — for low-modulus materials, use appropriate garter or cup springs to maintain contact under swell and temperature changes.
• Use of back-up rings — in high-pressure environments or where extrusion gaps exist, use PTFE or PEEK back-up rings to prevent seal extrusion.
• Surface finish and hardness — specify shaft hardness and surface finish (e.g., Ra 0.2–0.8 μm for many rotary seals) to reduce wear; avoid hard edges in grooves.
• Profile selection — lip geometry, secondary seals, or face seals can reduce fluid ingestion and extend life.
• Controlled start-up procedures — thermal and pressure ramping reduces mechanical shock to seals during start-up.
• Filtration and sealing barriers — remove particulates and use labyrinths or dust seals to reduce abrasive wear.

Testing and verification for rotary seals for chemical industry

Field-level compatibility checks are necessary because charts cannot capture every variable. Recommended verification steps:

1. Bench testing: age samples in the target fluid at expected temperatures for defined intervals (e.g., 24, 168, 720 hours). Measure hardness, tensile strength, dimensional change and leak rate.
2. Dynamic test rigs: run representative shaft speeds, pressures and temperatures with the chosen material and monitor torque, leakage and wear rate.
3. Small-scale field trials: install seals in a limited number of units under controlled monitoring to capture real-life interactions and maintenance data.

Documented test data is vital for E-E-A-T and procurement records; it supports warranty and continuous improvement programs.

Cost vs. reliability: making a commercial decision for rotary seals for chemical industry

While High Quality materials like FFKM and filled PTFE cost more upfront, their longer life and reduced downtime often yield lower total cost of ownership (TCO) in aggressive chemical processes. Use a simple TCO calculation that includes material cost, expected lifetime, labor for replacement, downtime cost per hour and environmental/safety compliance costs. Often the optimal choice reduces replacement cycles and unplanned outages.

Polypac: capabilities and why to consider them for rotary seals for chemical industry

Polypac is a scientific and technical hydraulic seal manufacturer and oil seal supplier specializing in seal production, sealing material development, and customized sealing solutions for special working conditions. Founded in 2008, Polypac began with filled PTFE seals (bronze-filled, carbon-filled, graphite PTFE, MoS₂-filled PTFE, glass-filled PTFE). Today Polypac's product line includes O-rings made from NBR, FKM, silicone, EPDM and FFKM.

Polypac's custom rubber ring and O-ring factory covers more than 10,000 m², with an 8,000 m² production space. Production and testing equipment are among the most advanced in the industry. Polypac maintains long-term cooperation with universities and research institutes domestically and internationally, which supports material development and application-specific testing.

Core products and advantages relevant to the chemical industry include:

• Product range: O-Rings, Rod Seals, Piston Seals, End Face Spring Seals, Scraper Seals, Rotary Seals, Back-up Rings, Dust Rings.
• Material expertise: filled PTFE, FFKM, FKM, NBR, EPDM, silicone and advanced specialty compounds.
• Customization: tailored compound development and seal geometry for specific chemicals, temperatures and pressures.
• Testing & R&D: in-house and partner lab testing for chemical ageing, dynamic wear and long-term compatibility.
• Manufacturing scale: high-volume capabilities combined with small-batch custom runs and fast prototyping.

Polypac's combination of material science, manufacturing capacity and academic collaboration makes it a viable partner when designing seals for demanding chemical industry applications. For consultation or to request tailored material tests and product samples, contact Polypac's technical sales team (see CTA below).

Step-by-step selection checklist for rotary seals for chemical industry

Use this checklist to move from problem definition to validated seal selection:

1. Record exact service conditions (fluid(s), Temp, Pressure, Speed, Motion).
2. Screen materials using compatibility guides to eliminate unsuitable options.
3. Shortlist 2–3 candidates balancing chemical resistance, temperature and mechanical needs.
4. Design gasket/seal geometry and specify surface finish/back-up rings/energizers.
5. Run accelerated ageing and dynamic bench tests at design conditions.
6. Perform a controlled field trial and collect life-cycle data.
7. Finalize material and geometry; document maintenance intervals and spare parts strategy.

Common pitfalls and how to avoid them when specifying rotary seals for chemical industry

• Relying solely on compatibility charts — always verify with testing under realistic conditions.
• Ignoring mixed chemicals and intermediate reaction products — mixture effects can be more aggressive than single chemicals.
• Underestimating temperature influence — chemical resistance can degrade rapidly with temperature rise.
• Not planning for permeation and vapour-phase attack — some fluids permeate even chemically resistant materials over time.
• Overlooking manufacturing tolerances and groove design — poor gland design causes extrusion and premature failure.

Frequently Asked Questions (FAQ)

1. Which material is best for seals exposed to concentrated acids and solvents?

Perfluoroelastomers (FFKM) and PTFE (including filled PTFE) offer the broadest resistance to concentrated acids and organic solvents. FFKM combines elastomer resilience with near-universal chemical compatibility, while PTFE provides excellent inertness and thermal stability. Cost and mechanical design considerations determine the optimal choice.

2. Can I use Viton (FKM) rotary seals in the chemical industry?

FKM (Viton®) is suitable for many hydrocarbon-based chemicals, fuels and oils and for moderately aggressive fluids at elevated temperatures. However, it performs poorly with strong amines, ketones (e.g., acetone), and certain polar solvents. Always consult compatibility data and test for your specific fluid mix and temperature.

3. How do I prevent extrusion of soft seals under high pressure?

Use back-up rings made of PTFE or PEEK to block extrusion gaps. Increase gland support, reduce extrusion gap, or select a harder/semi-filled material. Properly dimensioned back-up rings and groove geometry are critical.

4. Are tests mandatory before full-scale deployment?

Yes. Bench ageing, dynamic testing and limited field trials are strongly recommended. Charts give guidance but cannot replace real-world verification—especially for mixed chemicals, elevated temperatures, or long service intervals.

5. What are filled PTFE grades and when should I specify them?

Filled PTFE includes fillers like bronze, carbon, glass, graphite or MoS₂ to improve wear resistance, reduce cold flow and improve frictional properties. Use filled PTFE when low friction and chemical resistance are both required, particularly for face seals, rotary shafts and where sliding wear is significant.

6. How does temperature change affect chemical compatibility?

Higher temperature typically accelerates chemical attack, increases permeation rates and can change swelling behavior. A material compatible at room temperature may fail at elevated temperatures. Validate compatibility at the maximum expected service temperature.

7. Who should I contact to get custom testing and material development?

Polypac offers material development, custom seal design and application testing. For consultation, material samples, or to request a quotation, reach out via Polypac's website or contact the technical sales team (see CTA below).

Contact & product consultation (Call to Action)

For tailored advice, application-specific compatibility testing, or to order samples and custom rotary seals for chemical industry applications, contact Polypac. Polypac provides engineering support, material development and full-scale testing to ensure your seals meet chemical, thermal and mechanical demands. Visit https://www.polypac.com or email info@polypac.com to start a consultation and request product data sheets for O-Rings, Rod Seals, Piston Seals, End Face Spring Seals, Scraper Seals, Rotary Seals, Back-up Rings, and Dust Rings.

References

1. Parker Hannifin - Parker O-Ring Handbook. Accessed 2025-11-26. https://www.parker.com/literature/O-Ring%20Division%20English/Parker%20O-Ring%20Handbook.pdf
2. Trelleborg Sealing Solutions - Chemical Resistance Guide and Seal Selection. Accessed 2025-11-26. https://www.trelleborg.com/en/seals
3. Cole-Parmer - Chemical Resistance Database. Accessed 2025-11-26. https://www.coleparmer.com/


4. MatWeb Material Property Data - PTFE, FKM, EPDM and PEEK datasheets. Accessed 2025-11-26. https://www.matweb.com/
5. DuPont - Viton® (FKM) Fluoroelastomers product information. Accessed 2025-11-26. https://www.dupont.com/
6. Polypac corporate and product information (company-provided technical overview and history). Accessed 2025-11-26. https://www.polypac.com/