Capillary Flow Porometer for Membrane and Filter Pore Size

What is the Capillary Flow Porometer for Membrane and Filter Pore Size?

An automated instrument that wets a sample with a low surface tension liquid and measures gas flow versus pressure through wet and dry states. It reports bubble point, mean flow pore size and pore size distribution of through pores in membranes, filters and nonwovens.

Overview

A capillary flow porometer clamps a disc of wetted sample in a holder and increases gas pressure across it. The first flow detected gives the bubble point, which corresponds to the largest through pore, while the wet curve is compared with the dry curve to find the mean flow pore diameter at the pressure where wet flow is half dry flow. Only pores that are open on both sides are measured, unlike mercury intrusion, so the result is relevant for filtration. Wetting fluids such as Galwick with a surface tension of about 16 mN/m allow pore detection from about 13 nm to 500 µm. Test times are 5 to 15 minutes, there are no toxic liquids, and the sample is not crushed by high pressure.

How does it work?

Mercury porosimetry exploits the fact that mercury does not wet most solids, so it enters pores only under pressure. The Washburn equation relates the applied pressure to the pore throat diameter, D = −4γcosθ/P, using a surface tension of 485 mN/m and a contact angle of about 130°. Pressure is increased stepwise from vacuum to 400 MPa while the intruded volume is recorded by a capacitance dilatometer, and extrusion on depressurization shows pore connectivity. Capillary flow porometry instead wets the sample with a low surface tension liquid and records the gas pressure needed to blow liquid from pores, giving through-pore size. Gas permeability systems measure flow through a sample at a known pressure difference, and helium pycnometers determine skeletal volume.

What are the key features?

• Automated pressure ramp with precision mass flow and pressure sensors
• Wet-up and dry-up curve analysis for bubble point and mean flow pore size
• Low surface tension wetting liquids for pore detection down to 13 nm
• Sample holders for 25 mm and 47 mm discs and cartridges
• Report of pore size distribution by flow fraction
• Compliance with ASTM F316 and ASTM E1294 methods

What are the technical specifications?

A typical capillary flow porometer for membrane and filter pore size configuration offers pore size range of 0.013–500 µm, maximum pressure of 0–35 bar (up to 200 psi), pressure accuracy of ±0.15% of reading, flow range of 0–200 L/min, sample diameter of 8–47 mm discs; cartridges optional and wetting liquid surface tension of ≈ 16 mN/m. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Capillary Flow Porometer for Membrane and Filter Pore Size is used in membrane and filter QC, sterilizing-grade filter integrity, nonwoven and paper pore size and fuel cell gas diffusion layers. Across the wider Porosimeters class, laboratories also deploy it for ceramic and refractory pore analysis, filter and membrane pore size testing and catalyst pellet macropore distribution.

Which standards and certifications apply?

Relevant standards and methods include ISO 15901-1, ASTM D4284, ASTM D4404, ASTM F316 and ASTM D6226. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Mercury instruments need containment for vapor and spills, a dedicated sink or waste procedure, and staff training under local regulations. Samples must be dried and sized to fit penetrometers, and results depend on the assumed contact angle and surface tension. Correct for mercury compression and penetrometer expansion with blank runs. Calibrate pressure transducers annually and verify with a reference material of known pore size. Capillary flow systems need wetting liquids with documented surface tension and clean, dry gas. Place high-pressure units on a rigid bench and follow pressure vessel inspection rules.

How do I select the right Capillary Flow Porometer for Membrane and Filter Pore Size?

Select this variant when through-pore size governs performance, as with membranes, cartridges and gas diffusion media. It is not suited to dead-end or closed pores. In an RFQ, specify sample sizes or cartridge formats, required pore range, pressure limit, wetting liquid and whether standard ASTM F316 reporting is needed.

How does it compare with other Porosimeters variants?

Choose by pore size range, sample form and the quantity that the specification reports. Mercury intrusion covers a broad span, about 3.6 nm to 400 µm, and suits rigid ceramics, rocks, cement and catalysts pellets. It is unsuitable for compressible or amalgamating samples and requires mercury handling controls. Capillary flow porometers suit membranes and filters where through-pore bubble point and mean flow pore size are required. Gas permeability testers give Darcy permeability of rocks and ceramics. Helium pycnometers supply true density and closed porosity. Check the number of high-pressure ports, maximum pressure, penetrometer volume options, automation, and whether reporting follows ISO 15901-1, ASTM D4284 or ASTM F316.