Gas Pycnometry (Pycnometry)

Table reports the computed skeletal density for a commercially available nylon sample, produced from volume measurements taken from an Anton Paar Ultrapyc 5000 pycnometer. It has been previously demonstrated that increased nylon crystallinity correlates to increased skeletal density, which suggests that Sample 1 may be slightly more crystalline than the other nylon samples. This hypothesis was separately validated in another study.

Gas Pycnometry is one of the most widely used techniques for analyzing the true and skeletal density of any solid (even ones which are porous, granular, and irregularly shaped!). It provides fast, high-accuracy volume measurements that can be used to calculate density and porosity and can be adapted to analyze the purity, quality, volatile organic content, and stability of certain materials.

Covalent uses an industry-leading Ultrapyc 5000 Gas Pycnometer from Anton Paar for true density analysis. This tool achieves best-in-class accuracy across ranged sample types, including coatings, polymer foams, cement, mining, pharmaceuticals, ceramics, catalysts, metallurgy, and more.

Strengths

Unmatched volumetric measurement accuracy
Excellent reproducibility and reliability
Flexible analytical modes for wide array of sample types
Raw measurement can be used to calculate numerous material properties

Limitations

Density must be calculated using separately measured sample mass
Porosity does not include closed pores (e.g. pores which are not permeable through solid surface)

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Example Outputs Instruments Used How Pycnometry Works

Gas Pycnometry Services

Gas Pycnometry

Gas Pycnometry is one of the most widely used techniques for analyzing the true and skeletal density of any solid (even ones which are porous, granular, and irregularly shaped!). It provides fast, high-accuracy volume measurements that can be used to calculate density and porosity and can be adapted to analyze the purity, quality, volatile organic content, and stability of certain materials.

Covalent uses an industry-leading Ultrapyc 5000 Gas Pycnometer from Anton Paar for true density analysis. This tool achieves best-in-class accuracy across ranged sample types, including coatings, polymer foams, cement, mining, pharmaceuticals, ceramics, catalysts, metallurgy, and more.

Sample Requirements

Solids, powders, or battery materials
As little as 0.25 cm³ required

Example Outputs

The table reports computed skeletal density for a commercially available nylon sample, produced from volume measurements taken from an Anton Paar Ultrapyc 5000 pycnometer. It has been previously demonstrated that increased nylon crystallinity correlates to increased skeletal density, which suggests that Sample 1 may be slightly more crystalline than the other nylon samples. This hypothesis was separately validated in another study.

From: Anton Paar

Instruments Used

Anton Paar Ultrapyc 5000 Micro

Chamber Volume:
- Micro cell: 4.5 cm³
- Meso Cell: 1.8 cm³
- Nano Cell: 0.25 cm³
Volume Accuracy:
- Micro Cell: 0.10 %
- Meso Cell: 0.30 %
- Nano Cell: 1.00 %
Volume Repeatability:
- Micro Cell: 0.05 %
- Meso Cell: 0.15 %
- Nano Cell: 0.50 %
Preparation Modes: Flow, Pulse, Vacuum
Pressure Resolution: 0.0001 psi
Transducer Accuracy: better than 0.1 %

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How Pycnometry Works

Gas pycnometry evolved from Archimedes’ Principle of Displacement to measure the volume of solid materials with high accuracy using gas exchange. This value is then combined with the sample’s known mass to determine its true density.

To make a pycnometry measurement, a sample is loaded into a specialized chamber with known total volume. This chamber is exposed to an inert gas with known pressure – typically Helium – which will flood the space around the solid sample – including any penetrable pores. After the pressure stabilizes, a valve opens between the sample chamber and a reference chamber (with known volume). The Pycnometer measures the drop in pressure that occurs as the gas expands into the second chamber, and this pressure difference is used to calculate the true density of the sample.

Beyond the true density measurement, skeletal density, purity, porosity, and other properties can be analyzed using more advanced measurement procedures or through further data processing and computation.

If geometric volume is known, as can be the case for rigid solid foams, then the difference between the pycnometric and geometric volumes can be used to calculate open cell percentage. Compressibility and cell fracture can be subsequently analyzed using multiple-pressure experiments.