Summary
- FEP is rated better with
- Phenols (+100 points); Mineral acids (+95 points); Organic acids (+66 points); Oxidising agents and halogens (+57 points); Amines and nitrogen compounds (+26 points); Salts and salt solutions (+24 points); Alkalis (+24 points); Esters and ethers (+12 points)
- Within 10 points of each other
- Alcohols and glycols; Ketones and aldehydes; Aromatic hydrocarbons; Fuels, mineral oils and aliphatic hydrocarbons; Vegetable and animal oils, fats, essential oils; Halogenated hydrocarbons; Foods and beverages
Points are the difference in the share of rows rated A or B.
The two materials
Acetal (POM)
Polyoxymethylene (acetal)
Acetal (POM) resists many organic solvents and fuels. Strong acids and oxidising agents degrade it.
Rated rows: 956. A 41 %, B 32 %, C 12 %, D 15 %
FEP
Fluorinated ethylene propylene
FEP has nearly the chemical resistance of PTFE and can be melt-processed. Its service temperature, about 200 °C, is lower than that of PTFE.
Rated rows: 908. A 99 %, B 0 %, C 1 %, D 0 %
Share of rows rated A or B, by chemical class
How often the two ratings agree
Chemical classes were assigned by this site, not by the source. Mixtures and trade products without a clear class are not counted.
By chemical class
| Chemical class | Acetal (POM): rated A or B | FEP: rated A or B |
|---|---|---|
| Mineral acids | 5 % (63 rows) | 100 % (55 rows) |
| Organic acids | 34 % (64 rows) | 100 % (64 rows) |
| Alkalis | 76 % (21 rows) | 100 % (18 rows) |
| Salts and salt solutions | 76 % (197 rows) | 100 % (197 rows) |
| Oxidising agents and halogens | 43 % (63 rows) | 100 % (52 rows) |
| Alcohols and glycols | 96 % (57 rows) | 100 % (57 rows) |
| Phenols | 0 % (14 rows) | 100 % (14 rows) |
| Ketones and aldehydes | 91 % (35 rows) | 100 % (33 rows) |
| Esters and ethers | 88 % (68 rows) | 100 % (69 rows) |
| Amines and nitrogen compounds | 74 % (38 rows) | 100 % (38 rows) |
| Aromatic hydrocarbons | 100 % (14 rows) | 100 % (14 rows) |
| Fuels, mineral oils and aliphatic hydrocarbons | 96 % (73 rows) | 100 % (74 rows) |
| Vegetable and animal oils, fats, essential oils | 100 % (45 rows) | 100 % (47 rows) |
| Halogenated hydrocarbons | 80 % (70 rows) | 90 % (49 rows) |
| Foods and beverages | 100 % (46 rows) | 100 % (46 rows) |
Where the ratings differ most
Rows where the two ratings at 20 °C are at least two grades apart: 237 in total, the first 40 shown.
| Chemical | Concentration | Acetal (POM) | FEP |
|---|---|---|---|
| Acetic Acid | 100 % | D | A |
| Acetic Acid | 90 % | D | A |
| Acetyl Chloride | 100 % | D | A |
| Aluminum Chloride | saturated | D | A |
| Ammonium Bifluoride | 50 % | D | A |
| Antimony Trichloride | 90 % | D | A |
| Antimony Trichloride | aqueous | D | A |
| Arsenic Acid | aqueous | D | A |
| Battery Acid | 38 % | D | A |
| Benzenesulfonic Acid | saturated | D | A |
| Bismuth Chloride | D | A | |
| Bisulfite Liquor | D | A | |
| Bisulfite Liquor with SO2 | saturated | D | A |
| Bromine | D | A | |
| Bromine Vapors | D | A | |
| Bromoform | D | A | |
| Butylphenol | 100 % | D | A |
| Butyric Acid | D | A | |
| Calcium Bisulfite | saturated | D | A |
| Calcium Bisulfite | aqueous | D | A |
| Calcium Hypochlorite | D | A | |
| Calcium Hypochlorite | aqueous | D | A |
| Chlorine | 10 % wet | D | A |
| Chlorine | 97 % | D | A |
| Chlorine Gas | D | A | |
| Chlorine Water | D | A | |
| Chloroacetic Acid | D | A | |
| Chloroacetic Acid | 50 % | D | A |
| Chloroform | 100 % | D | A |
| Chromic Acid | 10 % | D | A |
| Chromic Acid | 20 % | D | A |
| Chromic Acid | 50 % | D | A |
| Cresol | D | A | |
| Dichloroacetic Acid | 50 % | D | A |
| Dichloroacetic Acid | technical grade | D | A |
| Dichloroethylene | technical grade | D | A |
| Fluorine | D | A | |
| Fluorosilicic Acid | 32 % | D | A |
| Formic Acid | 50 % | D | A |
| Formic Acid | 98-100 % | D | A |
Rating scale
- A very good resistance
- B good resistance
- C limited resistance
- D not resistant
- – no data
- K no general statement possible
A rating marked * is an estimate in the source, not a test result. An estimate is given as one value without a temperature.
More comparisons
Frequently Asked Questions
Is Acetal (POM) or FEP more chemical-resistant?
Of 889 chemicals rated for both materials at 20 °C, Acetal (POM) and FEP share the same rating in 355 rows (40 %). Acetal (POM) is rated better in 6 rows and FEP in 528 rows.
How do Acetal (POM) and FEP compare for chemical resistance?
Based on 889 chemicals tested for both: Acetal (POM) is rated better with –. FEP is rated better with Phenols, Mineral acids, Organic acids, Oxidising agents and halogens. They perform similarly with Alcohols and glycols, Ketones and aldehydes, Aromatic hydrocarbons, Fuels, mineral oils and aliphatic hydrocarbons.
About this data
The ratings come from the chemical resistance list published by Bürkle GmbH, which compiled them from raw-material manufacturers’ data. They describe laboratory tests on the raw material at 20 °C and 50 °C.
A finished part also sees pressure, mechanical stress, welds and mixtures that a laboratory test does not. Treat the rating as a first filter and test under your own conditions before relying on it.