SPI-Pore™ Standard White Polycarbonate "Track Etch" Screen Membrane Filters

Extensive back up information about the SPI-Pore brand of membrane filters for laboratory and manufacturing use

We present here, for the convenience of our customers, a table of membrane properties as a function of pore size. We would point out that anyone who has made such measurements knows that there is obviously an unknown "standard deviation" in these numbers, however, we do not have available sufficient data to report standard deviations. Hence, to be on the safe side, we always recommend that these numbers be viewed as "nominal" values, as a rough guide as to what they really are, but should not be taken to have been rigorously measured and determined.

How parallel are the pores?
This is an obvious parameter that one just does not hear much about, but clearly it should not be ignored. After all the parallelism of the pores becomes important in terms of determining pressure drop across the membrane filter.

The graphic to the right is, in a sense, a "corrosion cast" of a SPI-Pore™ membrane filter. A cast was made of the membrane filter, the PCTE membrane dissolved out, leaving the "cast" intact. Hence where there was a pore is not a "rod". Note the high uniformity of diameter from one side of the membrane to the other. When one is considering quality in a membrane, they should ask for this kind of information. PCTE membrane filters made by others have a different pore profile, and in our opinion, not as favorable in terms of pressure drop and filtration.

Spatial arrangement of the pores in
SPI-Pore™ PCTE membrane filters

Pore Size (µm)	Pore Density (pores/cm²)	Nominal Weight (mg/cm²)	Nominal Thickness (µm)	Bubble Point² (psi)	Typical Water^a (ml/min/cm²)	FlowRates Air^b (l/min/cm²)
20	4x10⁴	0.1	3	< 1	1100	80 ł
14	5x10⁴	0.6	6	< 1	2000	85 ł
12	1x10⁵	0.9	8	< 2	3000	85 ł
10	1x10⁵	1.1	10	< 2	1400	40 ł
8	1x10⁵	0.8	7	< 2	1300	40 ł
5	4x10⁵	1.1	10	3	650	40 ł
3	2x10⁶	0.9	9	5	600	50 ł
2	2x10⁶	1.1	10	7	170	22
1	2x10⁷	1.1	11	14	170	25
0.8	3x10⁷	0.9	9	18	120	20
0.6	3x10⁷	1.0	9	24	83	10
0.4	1x10⁸	1.0	10	36	41	10
0.2ą	3x10⁸	1.1	10	72	17	4
0.1	4x10⁸	0.7	6	> 100	2	2
0.08	4x10⁸	0.7	6	> 100	1	1
0.05	6x10⁸	0.7	6	> 100	0.4	0.5
0.03	6x10⁸	0.7	6	> 100	0.2	0.1
0.01	6x10⁸	0.7	6	> 100	< 0.1	0.01

^a Initial flow rates in mL/min/cm˛ using prefiltered water at 10 psid (0.7 kg/cm˛), ± 35% depending on test methodology

^b Initial flow rates in L/min/cm˛ using prefiltered air at 10 psid (0.7 kg/cm˛)

¹ "Regular" flow grade. Low pore density grade available on special order and requiring order minimums

² Calculated water bubble point, typical values (assuming 55° contact angle)

³ Differential pressure, 5 psi (0.35 kg/cm˛)

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