What Is Mercury Intrusion Porosimetry and When Is It Used?
Cody Langellier – Laboratory Division Manager
You need to characterize the pore structure of your product, but you’re unsure of how best to do so. You’ve done your research and found a technique called Mercury Intrusion Porosimetry (MIP) but it’s unclear if this is an appropriate test for your needs. How do you proceed?
The experts at Particle Technology Labs (PTL) are happy to guide you completely through the process. We answer commonly asked questions below for those interested in gaining a deeper understanding of MIP:
What is Mercury Intrusion Porosimetry?
Mercury Intrusion Porosimetry is a technique that utilizes mercury to probe the surface accessible pores of a solid or powder material. Mercury is an ideal probe chemical because it is a non-wetting liquid that requires external pressure to fill voids in the surface of a sample. By volumetrically measuring the quantity of mercury forced into the pores of a sample at a given pressure, we can determine the pore size, pore volume and porosity of your sample. Pore size is inversely proportional to the amount of pressure required to force the mercury into the sample pore. Large pores require less pressure to fill with mercury than smaller pores.
MIP can be used to characterize pore diameters in the size range of 4nm to 200µm. In contrast, classical gas adsorption techniques can measure pores no larger than 300nm. This makes the MIP technique an ideal candidate for samples with larger pore structures. These pores must be open pores, meaning they are surface accessible. This is not an ideal technique for microporous materials (pore diameters < 2nm) or materials in which the primary pore characterization desired is of through-pores, such as filter media. Have no fear, Particle Technology Labs offers alternative testing solutions for these material types with our gas adsorption instrumentation and our newly acquired Anton Paar Porometer.
What Data Will I Receive With an MIP Test?
When your sample is analyzed via the MIP technique, you will receive a comprehensive report including a tabular pore size and pore volume distribution report. Further, a summary page will be provided that will include the following measurements: total intrusion volume of Hg (mL/g), total pore area (m2/g), volume median pore diameter (µm), bulk density (mL/g), skeletal density (mL/g), and porosity. See a sample report.
When Not to Use the Mercury Intrusion Porosimetry Technique
Not all samples are appropriate for this technique. MIP is a destructive analysis. Your sample will be contaminated with Hg at the conclusion of testing. This should be considered if your sample is unique or in short supply. Metallic samples are not ideal as mercury can potentially amalgamate with metals under pressure. If your sample is composed of small pore diameters (<0.5µm) it must be sufficiently robust to withstand high pressure. Pores in the size range of 0.5µm to 4nm experience a pressure range of 500-60,000 psia. If a material is fragile, the pore structure can warp or fracture from intruding mercury at high pressures.
This does not preclude fragile samples from being tested by MIP. Our experts here at Particle Technology Labs can help establish appropriate testing conditions to eliminate sample compression if your material does not contain these small pores. If you have any questions about the suitability of your sample for this technique, please do not hesitate to contact us PTL provides consultations for testing inquiries free of charge and we are always happy to discuss your testing needs.
What Industries Use MIP Testing?
Particle Technology Labs has used the MIP technique to resolve testing issues across multiple industries. Our data has helped numerous companies resolve manufacturing process issues, track quality control across multiple sample lots, and evaluate environmental effects of, stored, finished products.
The petrochemical industry commonly uses this technique to characterize catalyst support substrates such as silica and alumina zeolites. Pharmaceutical companies have used this technique to characterize the performance of tablets and capsules pressed at differing pressures. Biomedical companies commonly use this test to characterize graft and implanting matrix materials for bones and teeth. We’ve even characterized dried mud and rock cores for environmental studies. The point is, MIP is a valuable technique for characterizing the pore structure of your material regardless of the application.
Why Choose Particle Technology Labs?
PTL is a fully independent, cGMP compliant and ISO accredited laboratory. Our lab has nearly 30 years of experience in the particle characterization field. As an independent laboratory, we offer a variety of instruments, manufactured by multiple vendors. We pride ourselves on our independence and strive to ensure that your samples are analyzed with the appropriate technique on the most suitable instrument for your sample. This commitment is seen in our continued effort to expand our instrument offerings. Particle Technology Labs recently acquired an Anton Paar Poremaster instrument. This acquisition expands our MIP offerings to allow customers a choice of manufacturer if deemed necessary by an existing test method or your preference.