The authoritative public forum
  for Metal Finishing since 1989
  

  -----

How to dissolve Teflon filter paper

2006

hi,
can you please tall me how to dissolve Teflon filter paper. It will be very grateful for me. This filter paper is used to collect the particulates from air.

thanks,

Afsana Tazmin
Student - Dhaka-1217, Bangladesh

---

Hello, Afsana. Thanks for telling us what the filter paper is used for, but we would need to know what you mean by dissolve and why. What goal are you trying to accomplish.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

---

2007

Teflon is a trade name for PTFE
There are no practical solvents for PTFE and that is why it is used to filter very aggressive chemicals like the strongest acids.
It is also relatively expensive and I am a little surprised to find you using it to collect particulates from air.
A more common practice is to use a cellulose filter. This is then soaked in oil of the same refractive index to make it transparent so that the particles can be seen under a microscope.
If you need to dissolve the particles, it is more usual to collect them by bubbling the air through water or other solvent and not use a filter paper.

Geoff Smith
Hampshire, England

---

Hi sirs!
I'm planning to use Teflon filters to collect air particles.But I don't know which side of filter can be used to expose air particles? Because there are 2 sides of Teflon filter distinguished by plastic O-ring? The side with O-ring is exposed particles or the other is exposed particles?
And could you please tell me the smallest particle size can be collected by the Teflon 47 mm (pore size 2 um, Pall corporation), 25 lpm vacuum pump?.
And How does loading capacity of the Teflon filter is ?
Thank you very much!

Hung Dam Duy
institute of science & Techn - Gwangju, South of Korea
2007

---

You can try by dipping the parts in n-metil-2-pirolydone several hours, but I don't think you'll have any success....

NMP is the solvent used by Teflon manufacturers to make the Teflon dispersions for the coatings...... but keep in mind it is a dispersion.

Jordi Pujol
- Barcelona, Spain
2007

---

Hung
PTFE filters are absolute filters. That is they have holes of a specific (and quite accurate) diameter. If they have 2 micron holes, that is the minimum size that will be trapped.
Your question about load capacity raises an interesting point. When you have collected enough particles to cover the surface of the paper, it effectively becomes a depth filter. That is, new particles are trapped in the layer already coating the filter. In this case, the minimum particle size trapped is less as they are trapped in the channels between the particles in the first layer and this continues until all the channels are filled and the filter is totally clogged.

Geoff Smith
Hampshire, England
2007

While I am not positive, I think that the reason that you use teflon is so that you can use harsh acid, bases and some organic solvents to remove whatever it is in the air that you are looking for without destroying the filter and having to find a way to take the destroyed filter out of the analysis process.

James Watts
- Navarre, Florida
2007

Thank you very much for your really helpful answer Sir Geoff Smith.

Hung Dam Duy
Institute of Science & Tech. - Gwangju, South of Korea
2007

---

2007

Dear,

I'm going to use Teflon filters 46.2 mm to collect air particles. If I'm not mistake, this filter is able to collect particulate until 0.3 micrometer. Although it has pore size around 2 micrometer. Am I right?

For collecting particle, I'll use cascade impactor. It has specification like these:
4 stages and 1 stages for pressure tap and filter, and its cut-point diameters of each stage1-4 are 0.238, 0.173, 0.111, and 0.063 micrometer (respectively) in aerodynamic diameter

So, the questions are:
1. Is it okay for using teflon filter 46.2 mm at this impactor?If it is disable to use, could you tell me what is better one?
2. Is it okay if I use filter for each stage?

I hope you can help me. Thank you for your kindness..

HerlianEriska Putra
Indonesian Institute Of Sciences - Bandung, West Java, Indonesia

I would like to know a suitable solvent for Graphite and PTFE (poly tetra fluoro ethylene) for the preparation of electrodes .

Sathesh Asha
Institution - Coimbatore, Tamil Nadu, India
December 12, 2010