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Choosing a Tank Resin: HDPE, Polypropylene or PVDF
How HDPE, polypropylene and PVDF compare on temperature, chemical resistance and cost, plus an honest look at HDPE versus crosslinked polyethylene (XLPE).
At a glance
HDPE vs. Polypropylene vs. PVDF
The right resin depends on the chemical, its concentration, the temperature and your budget. Ratings below come from our chemical compatibility database; confirm your exact service with us.
| Resin | Temperature | Best for | Watch for |
|---|---|---|---|
| HDPE | Continuous service below 140°F | The most economical choice for a wide range of acids, caustics and water-based chemicals. The widest range of sizes. | Higher temperatures, and strong chemicals at elevated temperature. |
| Polypropylene | Continuous use up to 200°F | Hot liquids and chemicals such as sodium hydroxide. | Not recommended for concentrated (37%) hydrochloric acid. |
| PVDF (Kynar) | Up to 300°F in some applications | Aggressive and high-purity chemicals, and the hottest service. | Costs considerably more than HDPE or polypropylene. |
Each resin
Which Chemicals Each Resin Suits
HDPE
High-density polyethylene is rated A in our database for hydrochloric acid, sodium hypochlorite, ferric chloride, phosphoric acid, hydrogen peroxide, DEF, alum and liquid fertilizer. Our HDPE vertical tanks run from 25 to 20,000 gallons.
Polypropylene
Polypropylene handles hotter liquids than HDPE and is rated A for sodium hypochlorite under 20%, ferric chloride, phosphoric acid, DEF, alum and liquid fertilizer. It is rated B for hydrogen peroxide and C for 37% hydrochloric acid.
PVDF
Kynar PVDF is a fluoropolymer for aggressive, hot and ultra-clean service. It is rated A for hydrochloric acid, sodium hypochlorite, ferric chloride, hydrogen peroxide and DEF, and B for phosphoric acid.
HDPE vs. XLPE
HDPE vs. Crosslinked Polyethylene (XLPE)
Some manufacturers mold tanks from crosslinked polyethylene (XLPE) and present it as the better material for every chemical. Here is an honest comparison. Bailiff molds its polyethylene tanks from HDPE: Dow RESILITY™ DPDB-3220.
What XLPE is
XLPE is molded from a polyethylene that forms chemical links between its molecular chains during molding. ASTM D1998 calls these Type I tanks. HDPE tanks, whose chains are not linked, are Type II.
Where XLPE has an edge
New XLPE parts typically have higher impact strength, and ASTM D1998 allows Type I tanks a slightly higher continuous service temperature: below 150°F, compared with below 140°F for Type II.
Trade-offs
Because its chains are linked, XLPE can’t be re-melted. That means it can’t be recycled or welded. And as the study below shows, higher strength when new doesn’t always mean the material holds up better in chemical service.
Our resin
The HDPE We Mold With
Bailiff molds its HDPE tanks from Dow RESILITY™ DPDB-3220, a high-density polyethylene made for rotationally molded chemical, potable water and agricultural tanks. We consider Chevron Phillips Marlex® HMN TR-942 a comparable alternative. Here is how Dow’s published typical values compare with the minimums in ASTM D1998.
| Property | Dow DPDB-3220 (typical) | ASTM D1998 requirement |
|---|---|---|
| Stress-crack resistance (ASTM D1693, Condition A) | More than 500 hours | 500 hours minimum |
| Cold impact, 1/4 in. rotomolded wall | More than 195 ft-lb at -40°F | 90 ft-lb at -20°F for walls up to 1/4 in. |
| UV protection | UV-20+ stabilizer package | UV stabilizer required for outdoor tanks |
| Density | 0.942 g/cm³ | — |
| Compliance | FDA 21 CFR 177.1520(c)3.1a (with restrictions); NSF/ANSI 51 and 61 | — |
Values are Dow’s typical properties, not specifications. Compliance listings apply to the resin; ask us about the requirements for your application.
The ExxonMobil study
What ExxonMobil Found in Sulfuric Acid and Bleach
In a 2003 technical report, ExxonMobil Chemical compared rotationally molded HDPE and linear low-density polyethylene with natural and white crosslinked polyethylene. Samples were soaked in 97% sulfuric acid and in sodium hypochlorite kept above 12.5%, at about 70°F, for up to 4,000 hours, then tested for impact strength, ductility, elongation and stress-crack resistance.
| Test | HDPE | Crosslinked (XLPE) |
|---|---|---|
| Impact strength when new (-40°F) | 185 ft-lb | Over 200 ft-lb |
| Impact after 4,000 hours in 97% sulfuric acid | 129 ft-lb | 15–20 ft-lb, failing in a brittle way from 1,000 hours on |
| Stretch before breaking after 1,000 hours in sulfuric acid | More than 666% (no change) | About 64–73%, down from 481% and more |
| Impact after 4,000 hours in 12.5% bleach | 177 ft-lb, mostly ductile | 15–54 ft-lb, all brittle |
| Stress cracking in sulfuric acid at 122°F | No failures in 1,000 hours | Half the samples failed by 225–273 hours |
| Depth of chemical attack | About 6–15 microns | About 30–60 microns |
In short, the crosslinked samples started out tougher, but in these two chemicals the HDPE samples kept far more of their strength and flexibility over time. ExxonMobil cautioned that the results apply to the tested concentrations and conditions and should not be extended to other chemicals. The report predates current resins, so treat it as one data point, not the final word.
FAQ
Tank Resin Questions
Which tank material is best for my chemical?
Start with our chemical compatibility database, then consider temperature and budget. HDPE suits most water-based chemicals at the lowest cost. Polypropylene handles hotter liquids, and PVDF handles the most aggressive and highest-purity service. Send us your SDS and we’ll recommend the resin.
Is crosslinked polyethylene better than HDPE?
Not in every case. XLPE has higher impact strength when new and a slightly higher temperature limit, but in ExxonMobil’s tests in 97% sulfuric acid and 12.5% sodium hypochlorite, HDPE kept more of its strength and flexibility over time. The right choice depends on the chemical and conditions.
How hot can a plastic tank get?
For continuous service, HDPE tanks stay below 140°F, polypropylene can run up to 200°F, and PVDF up to 300°F in some applications. Concentration and the chemical itself can lower these limits, so tell us your operating temperature.
Why does PVDF cost so much more?
PVDF is a fluoropolymer that costs far more to produce than polyethylene or polypropylene. It’s worth it when the chemical, purity or temperature rules out the other resins.
Not Sure Which Resin You Need?
Send us your chemical, concentration, temperature and volume. We’ll recommend the resin, SG rating and fittings.