I have charged positively and negatively Teflon, approx 1mm thick, and teflon plumbing tape with classic method, as seen in many papers, with cathode at -10,000v 10mm gap and grid at -1000V, also other way around at 10,00v and 1000v but cannot get voltage to stay making good Electret. Using TREK 368 non contact meter to measure voltage on TEFLON. Has anyone done this successfully? Perhaps I need a better quality TEFLON or to prepare the surface to make it less conductive. Have tried doing this at a 100-200degC but no better.
I have a TREK 344 and it works very well for detecting surface charge distributions. I would guess it is rather similar to the 368 using a vibrating piezo probe, so it should work very well for these experiments.
I did some similar work on surface charge modification experiments for a project in the printer business long time ago. We used a TREK 610D amplifier that can generate fast 10kV pulses, since fast dV/dt and proper wave forms can be important in the polarization process. Also using very strong corona effects at higher voltages may help, we used a Spellman variable 70kV power supply for this. I suspect that it may be beneficial to induce some amount of "treeing" into the surfaces in order to get a good polarization effect.
Pluming tape is likely a poorly defined material and not tested for conductivity at all. A tape made for electrical insulation purposes is probably much better.
http://www.4taconic.com/en/products--tapes.php is one teflon tape supplier. Virgin PTFE is also available in fairly thin sheets from plastics supply houses, at least here in Sweden.
I also remember that that when using liquid electrodes, the particular solvent mixture can be important.
Hope any of this helps.
Yes Remi that is a good point about dust neutralising the charge. Silicon dioxide supposedly works well but I would have to vacuum deposit it, sputter it or some other process that is not available to me.
Perhaps using one of my favorite problem solving materials could help. Parylene is a process for coating stuff thinly and very uniformly with completely pinhole free and hihgh quality dielectric films by cracking and vacum depositing paracyclophane derivatives.
It is possible to make environmentally stable electrets directly out of the Parylene by strong corona charge implementation.One example is the old patent US4291245 A.
Perhaps it could also be used to cover Your teflon if You can make it stick. Maybe sodium or strong alkali treatment of the PTFE could help.
I am not great specialist in the requested field. However, one of my PhD students used siimilar technique as was recommended by R. Cornwall. It means, encapsulating the material and neutralizing the charge, changing the electrical field .
Hello.
Teflon is actually a good electret. Yet, we have noticed that large thicknesses give poor results compared to 25µm,50µm and 125µm-thick PTFE layers; so you can try these thicknesses. Thermal treatment is a good option to improve the stability. You can get more information in this paper: Cantilever-based electret energy harvesters, Smart Materials and Structures, 2011 / figure 17. Note that the rear face of the sample should be metallized.
In order to limit the effect of dust on the charge stability, you can simply put them into boxes.
Hope this will help.
SB
Hello Thomas ,
Seems this discussion some time ago already.
Sharing everybody with one related research paper in this topic:
https://www.researchgate.net/publication/265866120_PARYLENE_HT_FOR_ELECTRET_GENERATORS
PARYLENE HT FOR ELECTRET GENERATORS
from Caltech Prof.Tai
For reference.
Nelson Yang
from YSMTC Taiwan
YSMTC is producing Parylene HT(AF4) dimer material.
https://www.linkedin.com/in/nelsonyang/
Article PARYLENE HT FOR ELECTRET GENERATORS
Hi,
You can find the answer of your question exactly in my recent paper on the Teflon electret production as follows,
M. Sohrabi and A. Komijani, ”Modified single point-to-plane corona poling
rotating system for production of electret dosimeters,” in IEEE Transactions
on Dielectrics and Electrical Insulation, vol. 25, no. 2, pp. 448-456, April
2018.
doi: 10.1109/TDEI.2017.006642
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering