Pycnometry in Powder Research and Development
Pycnometry is widely used and seen as one of the most reliable and unrivaled non-destructive methods to gather accurate data on a particle’s true density, regardless of its porosity or other morphologies. The mechanism of obtaining data using pycnometer laboratory equipment is based on Boyle’s gas law, which measures the volume, and density utilizing gas displacement ratios, using either helium, nitrogen, or sulfur hexafluoride gases as a medium. The gas being used fills up any pores or voids of the powder or granulated particles that are being tested.
Pycnometery benefits
In powder research and development, the pycnomatic data of particles is crucial in industries related to nano-particle technology like ceramics, carbon, and additive manufacturing as well as pharmaceuticals, metallurgy, plastics, food and feeds, chemical additives etc. Therefore a particle’s true volume and density are fundamental in its characterization and usability in industry. For example, it is important to know a particle’s mesoporous textural properties such as its pore diameter, pore volume, and total particle surface area about the particle’s drug loading capacity. Another area of importance in collecting density data is to evaluate a product’s structural integrity. The pycnometric density of ceramic or carbon powders for instance can provide indications of possible issues about voids with particle skeletal structures. This could indicate problems with the powder characteristics or a problem somewhere in the fabrication techniques used or during the transport and storage of the bulk particle processing phase.
Pycnometry Mechanisms
Two types of pycnometers use different minimalistic mechanical parts to create pressure, either by valves or pistons. Expansion and comparison pycnometer systems both use inert gases, utilizing two chambers. One chamber for testing and the other to establish a baseline. When the test chamber is pressurized, a pressure sensor measures the gas displacement caused by the test particle’s density and any voids or surface pores which will show the particle’s actual volume compared to the control chamber. As a reminder, a particle’s density is defined differently if pore volumes are included or excluded from the sample.
Other factors to note are establishing proper equipment pre-testing values and calibrations, ensuring accurate meniscus lineup, maintaining a stable thermal test equilibrium, and not forgetting the particle’s purity and the gas used, including excluding possible foreign contaminates.
Controlling these factors is crucial in obtaining accurate and precise values of the particle sample, which if overlooked can negatively affect the final product on multiple levels.
Things to keep in mind when using pycnometers is that large samples volumes are required, therefore using expensive samples will be a costly testing endeavor, moreover due to their accuracy, pcynometers are a challenging feat to clean properly and dry ensuring they are contaminate-free for new sample test runs.
Possible pycnometers brands
In summary, pycnometers are an essential part of any laboratory setup. There are several brands that offer fully automated inert gas pycnometers. Companies such as Microtrax with their Belpycno L, the Porotec Pycnomatic made by Meritics, the AccuPyc II supplied by Micromeritics and the Ultrapyc made by Anton Paar all provide volume / density analysis.
Pycnometers are essential and affordable laboratory equipment that is easy to use and quick, which makes the process of generating measurements and collecting data a simple task that yields a lot of useful information. This data can give researchers insights into volume characteristics regarding a particle’s interactions and possible changes during processing and as a final product or function such as in vivo nanoparticle drug delivery systems.
