Glass Fiber Membrane Filters, GD-120, 35mm, 50/Pk
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| Water Flow (s) | 14 |
| Pressure Drop | 17 |
| Thickness | 0.51 mm |
| Binder | None |
| Max Operating Temp. | 500 °C |
| Pore Size Range | 0.9 μm, nominal |
| Diameter | 13 mm to 293 mm |
| Weight (g/m2) | 123 |
Applications
- Use as a prefilter
- Both analytical and gravimetric analysis
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Frequently Asked Questions
Q: What is the difference between hydrophilic and hydrophobic membrane filters?
The pores of microporous membrane filters act as small capillaries. When hydrophilic membranes come into contact with water, capillary action associated with surface tension forces causes the water to spontaneously enter and fill the pores. In this manner, the membranes are easily wetted and allow the bulk flow of water through the pores. Once wetted, hydrophilic membranes will not allow the bulk flow of air or other gasses, unless they are applied at pressures greater than the membrane’s bubble point.
Hydrophilic membrane filters are typically used with water and aqueous solutions. They can also be used with compatible non-aqueous fluids. Hydrophilic membrane filters are typically not used for air, gas or vent filtration since the filters would block flow if inadvertently wetted, by condensation for example.
When hydrophobic membranes come into contact with water, surface tension forces act to repel the water from the pores. Water will not enter the pores and the membranes will act as a barrier to water flow, unless the water is applied at pressures greater than the membrane’s water entry pressure. Low surface tension fluids, such as alcohols, can spontaneously enter and fill the pores of hydrophobic membranes. Once all the air in the pores is displaced, there are no longer any surface tension forces and water can easily enter the pores, displace the low surface tension fluid, and pass through the membrane. The membrane will then allow bulk flow of water for as long as the pore remain water filled. If the membrane is allowed to dry (i.e. air enters the pores), then it must be pre-wet with a low surface tension fluid again prior to use with water.
Hydrophobic membrane filters are typically used with compatible non-aqueous fluids. They are also commonly used as air, gas, or vent filters. Hydrophobic membrane filters are sometimes used with water or aqueous solutions; and, in these applications, they must first be prewet with a low surface tension, water miscible fluid prior to use.
Q: What are the advantages of glass fiber filters?
Glass fiber filters offer excellent thermal stability and can operate at high temperatures, making them suitable for demanding laboratory and industrial applications. They are particularly economical and effective as pre-filters, where they help extend the life of final membrane filters by capturing larger particles and high particulate loads.
Due to their high dirt-holding capacity and fast flow rates, glass fiber filters are commonly used in air and liquid filtration, sample clarification, and analytical applications. Their combination of high-temperature resistance, cost-effectiveness, and reliable pre-filtration performance makes glass fiber filter media a versatile choice across many filtration processes.
Q: What is the smallest pore size rating available for the glass fiber filters?
The smallest available pore size rating for the glass fiber filters is 0.3µm, as featured by the Advantec Grade GF75 and Sterlitech Grade A glass fiber filters. It is important to note that the glass fiber filters are nominally rated and it should be expected that some amount particles ≥0.3µm will pass through these filters.
Q: Do glass fiber filters shed?
To some extent, all glass fiber filters have the potential to shed some fibers. Acrylic resin bonded glass fiber filters typically shed much lower amounts of fibers compared to binderless glass fiber filters. The amounts of shed fibers not only depend on the grades of glass fiber media used but are also influenced by the application conditions. Shed fibers are not typically a concern in applications where the glass fiber filters are used as a prefilters for subsequent membrane filters.
Q: Do you need a Chemical Compatibility Chart?
We have a Chemical Compatibility Chart that you can use for reference.
Q: What is the difference between nominal and absolute pore size ratings?
Nominal pore size ratings provide a general indication of filter retention efficiency, meaning some particles equal to or larger than the stated pore size may pass through the filter. Nominal ratings can vary by manufacturer, so filters with the same nominal pore size may not offer equivalent filtration performance.
Absolute pore size ratings are determined through controlled particle or microbial retention testing and represent the smallest particles that are consistently retained by the membrane. These ratings are often correlated with bubble point specifications and are generally more comparable across manufacturers.
Important: Actual filtration performance depends on application conditions, even when using filters with absolute pore size ratings.
Q: What is the function of the binder in the glass fiber filters?
The acrylic (PMA) resin binder used in glass fiber filters significantly enhances their wet strength, improving durability during liquid filtration. This resin binder helps hold the glass fibers together, making resin-bonded glass fiber filters easier to handle and more resistant to fiber shedding.
As a result, glass fiber filters with an acrylic (PMA) binder provide more consistent performance and improved integrity in both laboratory and industrial filtration applications. When assessing chemical compatibility and application suitability, it is important to consider the presence of the acrylic (PMA) resin binder.
Q: What is the difference between pore size and porosity?
The pore size refers to the diameter of the individual pores in a membrane filter. Pore size is typically specified in micrometers (µm). Most membranes and filter media actually contain a distribution of pore sizes. Nominal pore size ratings typically refer to the predominant pore size of a filtration media; pores larger and smaller than the nominal rating may be present. Absolute pore size ratings typically refer to the largest pore size of a membrane and it is expected that all pores will be equal to or smaller than the absolute rating.
For the polycarbonate track-etch (PCTE) and polyester track-etch (PETE) membrane filters, porosity is the percent of the total surface area occupied by the pores; it typically ranges from <1% to 16%. For the other membrane filters, porosity is the percent of the total volume occupied by the pores; it typically ranges from 40 to 80%.
Q: I noticed that the listed equivalent glass fiber filters have different specifications. What is the reason for this?
Glass Fiber Filters have nominal pore size ratings. These ratings are not necessarily consistent between different manufacturers. Consequently, it is possible for glass fiber filters from different manufacturers to have equivalent retention characteristics while having different nominal pore size ratings.
Q: I have noticed that the glass fiber disk filters have a subtle texture difference between the sides - one side is somewhat rougher than the other. Does the orientation of the filters in the holder affect filtration performance?
As a result of the manufacturing process, one side of the glass fiber filters is indeed slightly rougher than the other side. This difference does not affect performance and users need not be concerned with filter orientation. The filters will exhibit similar retention and throughput regardless of which surface is facing upstream.
Q: How do I determine if my filter is compatible with my application?
You can find the Sterlitech compatibility guide. It is important to realize that application conditions, such as operating temperature, affect compatibility. Please contact us at [email protected] if you need assistance.
Q: What is a bubble point and how is it determined?
The bubble point is the minimum amount of pressure required to push air bubbles through the largest pore of a wet membrane. The bubble point is inversely proportional to the pore diameter, as the pore diameter decreases the bubble point increases and vice versa.
Retention efficiency of membrane filters can be directly measured by challenging the filters with suspensions of standard microorganism cultures or particles of known size. Unfortunately, such efficiency testing is necessarily destructive. However, since retention characteristics are dependent on pore size, it is possible to correlate destructive challenge testing results to non-destructive membrane bubble point tests. In this manner, the relationship between membrane pore size and membrane bubble point is empirically determined. Typically, a minimum bubble point can be determined and specified for a particular pore size rating. The bubble point specification is then used for quality control during membrane manufacture. The bubble point can also be used by the consumer as a nondestructive test to verify membrane integrity before and/or after use.
Q: What is DOP?
DOP is an abbreviation for dioctyl phthalate, a compound historically used to generate monodisperse aerosol particles for air filter testing and efficiency characterization. DOP aerosols produce particles with a highly uniform size of approximately 0.3 µm, which corresponds to the most penetrating particle size (MPPS) for many air filtration media.
Because of this consistency, DOP aerosol testing has been widely used to evaluate air filter retention and performance, including in standards such as ASTM D2986, Standard Practice for Evaluation of Air Assay Media by the Monodisperse DOP (Dioctyl Phthalate) Smoke Test.
Note: Due to health and safety considerations, DOP has largely been replaced in modern testing by alternative aerosols (such as PAO), but the term “DOP test” is still commonly used in the filtration industry.
Q: What is the difference between a depth filter and membrane filter?
Depth filters are constructed with relatively thick filtration media and typically have nominal pore size ratings >1µm. Due to their large void volume, they capture significant amounts of particulate within their pore structure.
Membrane filters are typically composed of polymers that have been chemically processed, resulting in highly porous thin films with microscopic pore structures. Membrane filters typically have absolute pore size ratings <1µm, with some exceptions. Because of their very fine pore structure, membrane filters tend to trap the majority of particles on the surface. However, smaller particles with diameters near or below the pore size rating can be captured within the membrane or pass through the membrane.
Q: How can I tell the difference between the separator papers and the membrane filters?
To ensure ease of use, the membrane filters as stacked in their packaging are interleafed with layers of separator paper. In most cases, the membrane filters will be white in color except for the track-etch membranes which are colorless and translucent. In some special cases, the membranes will be dyed dark grey to black in appearance. In all cases, the separator paper will be a different color than the membrane and is usually not white. Please contact us at [email protected] if you need assistance.
