Cyclopentane, n-pentane and isopentane are important blowing agents used in foam production. This article outlines their physical and chemical properties, specifications reported for selected commercial products, and principal applications.
The market specifications below refer to products from different suppliers and grades. They do not represent a single product standard or the specifications of any one manufacturer.
1. Cyclopentane
Physical and Chemical Properties
Cyclopentane is a colorless, transparent, volatile liquid with a gasoline-like odor. Commercial products should generally be free from particulate impurities and suspended matter.
| Property | Reference Value |
|---|
| Freezing point | −94°C |
| Boiling point | Approximately 49°C |
| Relative vapor density, air = 1 | 2.4 |
| Vapor pressure at 20°C | 36.6 kPa |
| Vapor pressure at 38°C | 69 kPa |
| Density at 20°C | Approximately 0.745 g/cm³. |
| Flash point, closed cup | −37°C |
| Autoignition temperature | 361°C |
| Explosive limits in air, vol.% (LEL–UEL) | 1.5%–8.7% |
| TLV-TWA | 600 ppm (600 cm³/m³), as reported in the source material |
Cyclopentane is flammable. TLV-TWA refers to the threshold limit value expressed as a time-weighted average; the applicable standard and edition should be confirmed before using this value for occupational exposure assessment.
Commercial Product Specifications
Cyclopentane products available in the Chinese market vary in composition, purity and impurity limits. The following table summarizes specifications reported for selected products.
| Parameter | Specifications Reported for Selected Market Products |
|---|
| Density | Typically 0.73–0.75 g/cm³; the measurement temperature should be confirmed against the corresponding supplier’s documentation |
| Cyclopentane content | Generally ≥92%; commonly ≥95%; approximately 81.3% for an individual product |
| Combined n-pentane and isopentane content | Maximum limits range from 2% to 3.5%, depending on the product |
| 2,2-Dimethylbutane or isohexane components | Maximum limits range from 1.5% to 4%; in some products, these components form the balance |
| n-Hexane content | Requirements range from not detected to ≤100 mg/kg |
| Benzene content | Commonly ≤1 mg/kg |
| Combined 2-methylpentane and 3-methylpentane content | ≤0.5% for some products |
| C4 and lighter components | ≤0.5% for some products |
| Water content | Requirements range from not detected to ≤150 mg/kg |
| Distillation range | Not specified for some products; 30–60°C for others |
| Total sulfur content | Not specified for some products; ≤50 mg/kg for some grades and ≤5 mg/kg for more stringent grades |
These limits belong to different commercial products and should not be combined into a single acceptance specification. A “not detected” result should be interpreted together with the relevant test method and detection limit.
Characteristics and Applications
The source material describes cyclopentane as having an ozone depletion potential (ODP) of zero and a global warming potential (GWP) of zero. This statement requires confirmation of its supporting reference and assessment basis, as noted below.
Cyclopentane is used as a blowing agent for rigid polyurethane foam, replacing CFC-11, a chlorofluorocarbon that damages the ozone layer. Its main applications include:
- CFC-free refrigerators and freezers.
- Cold-storage insulation.
- Pipeline insulation.
Cyclopentane has relatively low solubility in polyether polyols, and low-viscosity polyether polyols are generally used in formulations. It can also be combined with isopentane in cyclopentane/isopentane blends for polyurethane foam.
2. Pentanes
Physical and Chemical Properties
The pentanes discussed here are n-pentane and isopentane. Both are colorless, transparent liquids at room temperature with a mild odor. The commercial product requirements described in the source material include the absence of olefins, particulate impurities and free water.
| Property | n-Pentane | Isopentane |
|---|
| English name | n-Pentane | Isopentane |
| CAS number | 109-66-0 | 78-78-4 |
| Boiling point at 101.3 kPa | 36.1°C | 27.8°C |
| Relative density at 20°C | 0.63 | 0.62 |
| Flash point | −40°C | −56°C |
| Autoignition temperature | 260°C | 420°C |
| Explosive limits in air, vol.% (LEL–UEL) | 1.4%–7.8% | 1.4%–8.3% |
Commercial Product Specifications
Selected n-pentane and isopentane products available in the Chinese market have the following specifications.
| Parameter | n-Pentane Products | Isopentane Products |
|---|
| Density | Approximately 0.60–0.65 g/cm³ | Approximately 0.58–0.63 g/cm³ |
| Main component content | n-Pentane ≥95% | Minimum isopentane content requirements range from 90% to 95%, depending on the product |
| Cyclopentane content | ≤0.5% | Not stated in the compiled information |
| n-Pentane content | Main component | ≤4.0% |
| Total pentane content | Not stated for some products; ≥98.5% or ≥99.5% for others | Not stated for some products; ≥99% or ≥99.5% for others |
| C5 and heavier components | ≤0.5%, as stated in the source material; the component definition requires confirmation | Not stated in the compiled information |
| C4 and lighter components | Not specified for some products; ≤0.5% for others | Not specified for some products; ≤1% for others |
| Total sulfur content | Maximum limits range from 1 to 3 mg/kg, depending on the product | Maximum limits range from 1 to 5 mg/kg, depending on the product |
| Benzene content | ≤1 mg/kg for some products | Not stated in the compiled information |
Total pentane content refers to the combined content of n-pentane and isopentane. The different limits above correspond to different suppliers or grades, rather than an allowable variation within a single product.
Characteristics and Applications
n-Pentane and isopentane are obtained from oilfield light hydrocarbons through high-efficiency fractionation.
n-Pentane can be used as a desorbent in molecular sieve dewaxing processes. Blending n-pentane with isopentane in different ratios allows different foaming requirements to be met, with the blends serving as efficient blowing agents for expandable polystyrene (EPS).
n-Pentane and isopentane can also be blended with cyclopentane and other components for use as polyurethane (PU) blowing agents.
Technical Points Requiring Confirmation
- Cyclopentane density: The original record of 0.62–0.64 g/cm³ has been excluded from the cyclopentane specification table. Its product identity, composition and measurement temperature need confirmation before it can be assigned to a particular commercial grade.
- Environmental parameters: The original statement that both ODP and GWP are zero has been retained as a statement from the source material. The supporting reference and GWP assessment basis should be confirmed before publication.
- Explosive limits: The original numerical values have been retained. OSHA lists a cyclopentane LEL of 1.1%, rather than the 1.5% stated in the source material; the applicable source and test conditions therefore require confirmation.osha
- n-Pentane component limits: The reported limit of ≤0.5% for “C5 and heavier components” needs clarification because n-pentane itself is a C5 hydrocarbon. The original supplier documentation may contain an additional qualification.
- Occupational exposure limit: The stated TLV-TWA of 600 ppm requires confirmation of the applicable standard, jurisdiction and edition.
- Process terminology: “Molecular sieve dewaxing” has been retained from the original material. The specific process should be confirmed before introducing a more narrowly defined term.
- Data verification: Unless otherwise cited, the technical figures above have been retained from the supplied material rather than independently verified.