Cyclopentane Storage & Tank Compatibility

Storing Cyclopentane? Start Here

Cyclopentane (C₅H₁₀, CAS 287-92-3) is a clear, colorless, highly volatile aliphatic hydrocarbon and the simplest cyclic alkane in the C5 range. It is widely used as a blowing agent for rigid polyurethane foam insulation, as a precision cleaning and degreasing solvent, and as a feedstock in fine chemical synthesis. With a flash point near -37 C and a boiling point of about 49 C, it forms ignitable vapor-air mixtures at ordinary temperatures, so flammability controls dominate its handling. As a nonpolar hydrocarbon it is practically insoluble in water but mixes freely with most organic solvents. The same nonpolar character that makes it an effective solvent also drives it into the wall of polyethylene tanks, where it swells and weakens the resin, making material selection the central storage decision.

Is Cyclopentane Compatible with Polyethylene (HDPE / XLPE) Tanks?

No. Cyclopentane is not compatible with polyethylene storage tanks. Polyethylene resists water-based salts, acids, bases, and many polar solutions, but nonpolar aliphatic hydrocarbons such as cyclopentane are absorbed into the polymer matrix. The liquid permeates the wall, causes swelling and softening, lowers stiffness and burst strength, and can carry hydrocarbon vapor through the tank wall. Standard plastics resistance charts list aliphatic and aromatic hydrocarbon solvents as unsuitable (U) for both HDPE and crosslinked polyethylene (XLPE). For bulk cyclopentane, use carbon steel or stainless steel vessels rated for flammable liquids, with PTFE or Viton seals, full bonding and grounding, and proper vapor and emission controls. Polyethylene should not be used even for short-term storage.

Material compatibility at a glance

Cyclopentane is a low-boiling nonpolar aliphatic hydrocarbon that absorbs into and swells polyethylene and polypropylene, so HDPE and XLPE poly tanks are not suitable. Store and handle in carbon steel or stainless steel with PTFE, Viton, or nitrile seals, full bonding and grounding, and flame-rated electrical equipment due to the very low flash point.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Extremely flammable: vapor forms ignitable mixtures at room temperature; eliminate ignition sources and use flame-rated electrical equipment in storage and transfer areas.
• Bond and ground all containers and transfer lines; cyclopentane can accumulate a static charge during pumping and pouring.
• Provide local exhaust or open-air handling; vapors are heavier than air and can travel to a remote ignition source and flash back.
• If swallowed it can be aspirated into the lungs (H304); do not induce vomiting and seek medical attention immediately.
• Use chemical-resistant gloves, splash goggles, and a respirator where vapor concentrations may be high; avoid prolonged skin contact.
• Store in tightly closed, vapor-tight metal containers in a cool, well-ventilated area away from oxidizers and heat.

Common questions

Can I store cyclopentane in an HDPE or poly tank?

No. Cyclopentane is a nonpolar aliphatic hydrocarbon that is absorbed by polyethylene, causing swelling, softening, and loss of strength. HDPE and XLPE are rated unsuitable for hydrocarbon solvents. Use carbon steel or stainless steel rated for flammable liquids.

What is the NFPA 704 rating for cyclopentane?

Cyclopentane is rated Health 1, Flammability 3, Instability 0 per CAMEO Chemicals and the PubChem safety summary. The Flammability 3 reflects its very low flash point of about -37 C.

What tank and seal materials are suitable for cyclopentane?

Carbon steel and 304/316 stainless steel are suitable for the vessel. For seals and gaskets use PTFE or Viton (FKM); nitrile is generally acceptable. Avoid EPDM and all polyolefin plastics.

Why is cyclopentane so flammable?

It is a light, volatile hydrocarbon with a flash point near -37 C and a high vapor pressure, so it readily releases ignitable vapor at normal temperatures. Bonding, grounding, ventilation, and ignition-source control are essential.