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Polycarbonate Membrane Filters

SPI-Pore™ and Nuclepore® brands



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Appearance of the pores in the SPI-Pore™ PCTE membrane filters Corrosion cast of a typical SPI-Pore™ PCTE membrane filter showing the spatial arrangement of the pores.
SPI-Pore Polycarbonate Membrane Filters

Available Products:

Disc filters
Black Membranes (SPI Pore only)
Epifluorescence Microscopy
Grease Coated Membrane Filters
Membrane Filter Holders
Preloaded Membranes into ready-to-use cassette
Standard White Membranes (SPI-Pore and Nuclepore)

Special Membranes (Disks)
Grease Coated, Cascade Impact Collector Applications
PVP-Free Membranes for Chemotaxis

Sheet format
8" x 10" White Membrane Material, Cut Sheets


Why Polycarbonate Membrane Filters?

Ordinary depth-type membrane filters contain tortuous pores that capture particles via random entrapment. The result being the trapping of some fraction of particles in the interior (interstices) of the membrane filter, and therefore, unavailable for observation on the surface by LM or SEM.

In contrast, polycarbonate filters contain uniform, cylindrical pores, preferentially etched into the membrane, thus allowing for an even distribution of a collected sample in one plane across the entire exposed membrane surface.

Hence all samples are captured on a flat, smooth, featureless surface. The precisely sized pores in a very narrow distribution ensure accurate separation, or fractionation, of samples by size.

Contaminant-free, these microporous screens are biologically inert, offer excellent chemical resistance and thermal stability, provide superior strength and negligible adsorption of filtrate. These factors combined with the unique filtration capabilities of the polycarbonate membrane, make it a clear preference for a number of EM and LM applications, including: Airborne Particulate Analysis including asbestos, Chemotaxis, Cytology, Histology, Paleontology, Parenterals, and Water Analysis for asbestos and other suspended inorganics. The color of the most commonly purchased form of the product is white, but in some situations, the black form of the product is preferred.

The filtration and physical properties of PC membrane filters make them fairly unique and set them apart from membrane filters of other compositions, giving them in many instance, unique performance advantages. Consequently, in many general laboratory situations, many users of membrane filters elect to include an assortment of PC membranes on standby for when one of those unique kinds of situations arise and filtration must be done immediately.

Chemical Compatibility of PCTE membranes:
The membranes are surprisingly resistant to a number of organic solvents and inorganic liquids. But we must caution that some solvents will instantly dissolve PCTE membranes and you should consult our solvent resistance information.

Fluorescence characteristics
All PCTE membrane filters, irrespective of the manufacturer, so far as we know, are made from a polycarbonate that contains fluorescent pigmentation in the raw material. Again, to the best of our knowledge, this most important and unique raw material is not available without this pigmentation system. We have not studied exactly what wavelengths the fluorescence occurs, but we are pretty sure that a laser will light them up like a Christmas tree.

Birefringence:
All polycarbonate membrane filters, to our knowledge, exhibit some amount of birefringence and that is because polycarbonate crystallizes and therefore has a crystalline texture. In a polarizing microscope, the individual crystallites show up as a fine, barely resolvable "pepper" like appearance.

Maximum use temperature:
The polymer starts to soften at around 150°C and will actually melt at around 240°C. Should your requirements involve work at higher temperatures, we would recommend you consider either A) Anopore® aluminum oxide membrane filters or B) the SPI-Pore™ Silver Membrane Filters.

Do the membranes have a charge?
The polycarbonate track etch membranes do not have an inherent charge, either positive or negative. They do, however, act in the same way as the dielectric film in a capacitor, and static electricity will build up on it. This static charge will cause the membrane to act as if it has a charge, but that charge is not actually a property of the membrane; it is the result of the environment which the membrane has experienced. The Zerostat® antistatic gun has proved effective in terms of neutralizing any charge that might build up on a membrane.


SPI-Pore Polycarbonate Membrane Filters

SPI-Pore polycarbonate membrane filters are manufactured using unique proprietary manufacturing technology and also meet or exceed industry standards for high-grade polycarbonate membranes on all property levels:

Membrane characterization:
We have assembled, as a function of pore size, a large amount of information about the physical characteristics of the SPI-Pore track etch polycarbonate membrane filters, much more so that has been disclosed for membranes made by others.

SPI-Pore vs. Nuclepore Polycarbonate Track Etch Membrane Filters
To the first approximation, since there is only one manufacturer in the world of the special liquid monomer from which the polycarbonate film material is made, the two different brands of membrane filters are similar. But because different manufacturing processes are used to produce damage tracks that are then etched into the pores, different thicknesses of base material film are used. And that is why in general for most pore sizes, the membrane thickness for the SPI-Pore membranes this thinner than for the Nuclepore brand, and this can have important implications for flow rates.

Available Polycarbonate Membrane Filter Products

Disc filters
Black Membranes (SPI Pore only)
Epifluorescence Microscopy
Grease Coated Membrane Filters
Membrane Filter Holders
Preloaded Membranes into ready-to-use cassettes
Standard White Membranes (SPI-Pore and Nuclepore)

Special Membranes (Discs)
PVP-Free Membranes for Chemotaxis

Sheet format
8" x 10" White Membrane Material, Cut Sheets

Slit roll format

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Wednesday May 14, 2008
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