SPI Pore Grease Coated Polycarbonate Track Etch Membrane Filters, 47 mm Dia.,8.0um Pore Size Pk 100

Ever since the advent of certain polymer membrane filters, polycarbonate perhaps being the most prominent, there has been concern about the "stickiness" of the filter and the ability of the natural membrane, as manufactured, to "hold" caught particulates, especially those in the aerosol range. There has been the nagging concern that there could be some particle loss and the numbers eventually generated could be lower than what they actually are. 

Increasing the "stickiness" of the polycarbonate membrane filter surface is not an easy task and even once accomplished, and even though it is more "sticky", it enabling medium responsible for the increased stickiness can interfere with other aspects of the analysis. 

The solution:
The laboratory of Structure Probe, Inc. was harnessed to formulate a more "sticky" version of the polycarbonate membrane filter, especially for use in cascade impact collectors for the collection of particulates in the aerosol range. After more than two years of testing and evaluation, we believe we have a useful product. The size of the pores is not substantially reduced and the pressure drop across the membrane is not appreciably increased. Yet, we do have increased greatly the adhesion of particles in the aerosol range to the surface of the membrane filter. 

Shelf life:
The grease used, at room temperature, exhibits a very low vapor pressure, hence we do not believe this product will exhibit any kind of shortened shelf life. However all of our testing is not complete, consequently, we can guarantee the properties of the coated membranes for only two years from the manufacturing date. However, we have every reason to believe that the shelf life, in an unopened pack will be substantially longer than two years but at this point, we do not have hard data to back up that statement. 

Terms of sale:
The manufacturing of the SPI Supplies brand of grease coated membrane filters is labor intensive. It is also a manual operation. Hence we do know that there will be some variation from membrane to membrane. However, having said that, based on the beta testing that has been done so far, we don't think such product variation is of a magnitude such that it should be of any great concern to anyone. We will guarantee that the product will be as we have described, but we can not guarantee that it will perform as expected in any particular cascade impact collector or any other device for the collection of aerosol size particulates. The risk of performance is clearly to be carried by the customer, not by SPI Supplies. As a matter of corporate policy we do not send out free samples, but we will offer the possibility of purchasing a sample pack, each one containing 5 coated membrane filters.