What is the best diaphragm material for chemicals?

PTFE is the most chemically resistant diaphragm material, compatible with virtually all chemicals. However, PTFE has lower flex life than elastomers. For aggressive chemicals, use PTFE with Santoprene or Neoprene backing for improved durability.

How long do AODD pump diaphragms last?

Diaphragm life varies: Santoprene offers excellent flex life (millions of cycles), PTFE has moderate flex life but best chemical resistance, Buna-N and EPDM offer good flex life for specific applications. Typical replacement is 3-12 months depending on application.

What diaphragm is best for petroleum products?

Buna-N (NBR) or Viton (FKM) diaphragms are best for petroleum products. Buna-N is economical for general petroleum, while Viton offers higher temperature rating (up to 200°C) and better chemical resistance for aggressive fuels.

AODD Pump Diaphragm Material Selection Guide

Diaphragm Material Overview

Importance of Material Selection

The diaphragm is the critical component that:

Contains the process fluid
Provides pumping action through flexing
Must resist chemical attack
Must withstand temperature
Must have adequate flex life

Material Categories

Category	Materials	Characteristics
Thermoplastic Elastomer	Santoprene	Best flex life
Synthetic Rubber	Buna-N, EPDM, Neoprene, Viton	Good flex, specific compatibility
Fluoropolymer	PTFE	Best chemical resistance
Backed PTFE	PTFE + Elastomer	Combined benefits

PTFE (Polytetrafluoroethylene)

Overview

Also known as: Teflon®

Chemical Resistance: ★★★★★ (Best)
Flex Life:          ★★☆☆☆ (Lower)
Temperature Range:  ★★★★☆ (Wide)
Cost:               ★★★★★ (Highest)

Properties

Property	Value
Temperature range	-10°C to 100°C
Chemical resistance	Virtually universal
Flex life	Lower than elastomers
FDA compliance	Yes (available)

Chemical Compatibility

Compatible with:

All acids (HCl, H₂SO₄, HNO₃, HF)
All bases (NaOH, KOH)
All solvents (ketones, esters, chlorinated)
Hydrocarbons
Oxidizers

Not compatible with:

Practically nothing (most inert material)

Applications

Application	Why PTFE
Aggressive chemicals	Universal resistance
Pharmaceutical	FDA compliance, purity
Semiconductor	Ultra-clean
Mixed chemical service	Versatility

PTFE Variants

Type	Description	Benefit
Virgin PTFE	Pure, unmodified	Best purity
Modified PTFE	Enhanced properties	Better flex
Conductive PTFE	Carbon-filled	Static dissipation
Backed PTFE	With elastomer	Better flex life

Backed PTFE

Structure:
┌─────────────────────────┐
│   PTFE (fluid side)     │ ← Chemical resistance
├─────────────────────────┤
│   Backing elastomer     │ ← Flex life
│   (Santoprene/Neoprene) │
└─────────────────────────┘

Benefit: Chemical resistance + good flex life

EPDM (Ethylene Propylene Diene Monomer)

Overview

Chemical Resistance: ★★★★☆ (Good for acids/bases)
Flex Life:          ★★★☆☆ (Moderate)
Temperature Range:  ★★★★★ (Wide)
Cost:               ★★☆☆☆ (Moderate)

Properties

Property	Value
Temperature range	-50°C to 120°C
Chemical resistance	Acids, bases, alcohols
Flex life	Moderate
FDA compliance	Yes (available)

Chemical Compatibility

Compatible with:

Dilute and concentrated acids
Strong bases (NaOH, KOH)
Alcohols (methanol, ethanol, IPA)
Ketones (acetone - with caution)
Glycol-based fluids
Water and steam

Not compatible with:

Petroleum products
Mineral oils
Aromatic hydrocarbons
Gasoline, diesel

Applications

Application	Why EPDM
Chemical processing	Acid/base resistance
Water treatment	Wide compatibility
Food processing	FDA options
Paint and coatings	Solvent resistance

Santoprene (TPE)

Overview

Also known as: Thermoplastic Elastomer (TPE)

Chemical Resistance: ★★★☆☆ (Good general)
Flex Life:          ★★★★★ (Excellent)
Temperature Range:  ★★★☆☆ (Moderate)
Cost:               ★☆☆☆☆ (Low)

Properties

Property	Value
Temperature range	-40°C to 100°C
Chemical resistance	Good general
Flex life	Excellent (best)
FDA compliance	Yes (available)

Chemical Compatibility

Compatible with:

Dilute acids
Bases
Alcohols
Water-based fluids
General chemicals

Not compatible with:

Strong oxidizers
Concentrated acids
Aromatic hydrocarbons
Some chlorinated solvents

Applications

Application	Why Santoprene
General transfer	Cost-effective
Abrasive slurries	Wear resistance
High suction lift	Flexibility
Long pump life	Excellent flex

Santoprene Advantage

Flex Life Comparison:
Santoprene  ████████████████████ 100%
EPDM        ████████████ 60%
Neoprene    ████████████ 60%
Buna-N      ██████████ 50%
PTFE        ████████ 40%

Best choice when flex life is priority!

Neoprene (Polychloroprene)

Overview

Chemical Resistance: ★★★☆☆ (Moderate)
Flex Life:          ★★★★☆ (Good)
Temperature Range:  ★★★☆☆ (Moderate)
Cost:               ★☆☆☆☆ (Low)

Properties

Property	Value
Temperature range	-30°C to 90°C
Chemical resistance	Moderate
Flex life	Good
Weather resistance	Excellent

Chemical Compatibility

Compatible with:

Water (fresh and seawater)
Water-based slurries
Some oils
Refrigerants (R-12, R-22)

Not compatible with:

Esters
Ketones (acetone)
Strong acids
Chlorinated solvents

Applications

Application	Why Neoprene
Water transfer	Good compatibility
General purpose	Low cost
Outdoor use	Weather resistant
Slurries	Abrasion resistant

Buna-N (Nitrile, NBR)

Overview

Chemical Resistance: ★★★★☆ (Good for oils)
Flex Life:          ★★★☆☆ (Moderate)
Temperature Range:  ★★★☆☆ (Moderate)
Cost:               ★☆☆☆☆ (Low)

Properties

Property	Value
Temperature range	-40°C to 80°C
Chemical resistance	Petroleum-based fluids
Flex life	Moderate
Oil resistance	Excellent

Chemical Compatibility

Compatible with:

Petroleum products
Gasoline, diesel, kerosene
Hydraulic fluids
Lubricating oils
Alcohols
Water

Not compatible with:

Ketones
Esters
Chlorinated solvents
Strong acids and bases
Ozone exposure

Applications

Application	Why Buna-N
Petroleum transfer	Excellent oil resistance
Fuel handling	Hydrocarbon compatible
Hydraulic systems	Oil compatible
Low-cost general	Economical

Viton (FKM, Fluoroelastomer)

Overview

Chemical Resistance: ★★★★★ (Excellent)
Flex Life:          ★★☆☆☆ (Lower)
Temperature Range:  ★★★★★ (Highest)
Cost:               ★★★★★ (Highest)

Properties

Property	Value
Temperature range	-20°C to 200°C
Chemical resistance	Excellent (most chemicals)
Flex life	Lower than elastomers
Oil resistance	Excellent

Chemical Compatibility

Compatible with:

All petroleum products
Mineral acids
Aromatic hydrocarbons
Chlorinated solvents
Silicone oils
Most aggressive chemicals

Not compatible with:

Ketones (acetone, MEK)
Esters (ethyl acetate)
Ammonia
Organic acids (acetic)

Applications

Application	Why Viton
High temperature	Up to 200°C
Aggressive fuels	Excellent resistance
Chemical processing	Broad compatibility
Critical applications	Premium performance

Material Comparison Table

Quick Reference

Material	Temp (°C)	Chemical	Flex Life	Oil	Acid	Cost
PTFE	-10 to 100	★★★★★	★★☆	★★★★★	★★★★★	$$$$$
EPDM	-50 to 120	★★★★☆	★★★☆	☆☆☆☆☆	★★★★☆	$$
Santoprene	-40 to 100	★★★☆☆	★★★★★	★★☆☆☆	★★★☆☆	$
Neoprene	-30 to 90	★★★☆☆	★★★★☆	★★★☆☆	★★☆☆☆	$
Buna-N	-40 to 80	★★★☆☆	★★★☆☆	★★★★★	★★☆☆☆	$
Viton	-20 to 200	★★★★★	★★☆☆☆	★★★★★	★★★★☆	$$$$$

Chemical Resistance Chart

Chemical	PTFE	EPDM	Santoprene	Buna-N	Viton
Sulfuric Acid	A	B	B	D	A
Hydrochloric Acid	A	B	B	D	B
Sodium Hydroxide	A	A	A	C	B
Acetone	A	B	B	D	D
Gasoline	A	D	D	A	A
Diesel	A	D	D	A	A
Alcohols	A	A	A	B	B
Water	A	A	A	A	A

Legend: A = Excellent, B = Good, C = Fair, D = Not Recommended

Selection Guide

Selection by Fluid Type

Fluid Type	1st Choice	2nd Choice
Strong acids	PTFE	EPDM
Strong bases	EPDM	PTFE
Solvents	PTFE	Viton
Petroleum	Buna-N	Viton
Water	EPDM	Santoprene
General chemical	PTFE	Santoprene
Food/Pharma	FDA PTFE	FDA EPDM
High temp (>100°C)	Viton	PTFE
Abrasive slurry	Santoprene	PTFE

Selection Decision Tree

START: What is the fluid?
│
├─► Strong acids/bases?
│   └── YES → PTFE or EPDM
│
├─► Petroleum/oils?
│   └── YES → Buna-N or Viton
│
├─► Solvents?
│   └── YES → PTFE
│
├─► Temperature >100°C?
│   └── YES → Viton
│
├─► Abrasive/slurry?
│   └── YES → Santoprene
│
├─► General/water?
│   └── YES → Santoprene or EPDM
│
└─► Unknown/mixed?
    └── PTFE (safest choice)

Specification Format

=== DIAPHRAGM MATERIAL SPECIFICATION ===

Service: _______________
Tag: _______________

Process Conditions:
Fluid: _______________
Temperature: ___ °C (min/max: ___/___)
Chemical composition: _______________

Selected Diaphragm:
Material: □ PTFE □ EPDM □ Santoprene □ Buna-N □ Viton
□ Backed PTFE with ___ backing

Justification:
Chemical compatibility: □ Verified
Temperature rating: □ Adequate
Flex life: □ Acceptable
FDA compliance: □ Required □ Not required

Special Requirements:
□ Conductive (ATEX)
□ FDA compliant
□ USP Class VI
□ Other: _______________

Common Selection Mistakes

Mistakes to Avoid

Mistake	Problem	Solution
EPDM with petroleum	Rapid swelling/failure	Use Buna-N or Viton
Buna-N with ketones	Rapid degradation	Use PTFE
PTFE without backing	Short flex life	Use backed PTFE
Ignoring temperature	Premature failure	Check full temp range
Wrong Viton grade	Chemical attack	Verify specific grade

Diaphragm Material Overview

Importance of Material Selection

Material Categories

PTFE (Polytetrafluoroethylene)

Overview

Properties

Chemical Compatibility

Applications

PTFE Variants

Backed PTFE

EPDM (Ethylene Propylene Diene Monomer)

Overview

Properties

Chemical Compatibility

Applications

Santoprene (TPE)

Overview

Properties

Chemical Compatibility

Applications

Santoprene Advantage

Neoprene (Polychloroprene)

Overview

Properties

Chemical Compatibility

Applications

Buna-N (Nitrile, NBR)

Overview

Properties

Chemical Compatibility

Applications

Viton (FKM, Fluoroelastomer)

Overview

Properties

Chemical Compatibility

Applications

Material Comparison Table

Quick Reference

Chemical Resistance Chart

Selection Guide

Selection by Fluid Type

Selection Decision Tree

Specification Format

Common Selection Mistakes

Mistakes to Avoid

❓Frequently Asked Questions

📚References & Sources

🔗Related Articles

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