News
Worldwide customers: "Glindemann PTFE Sealing Rings" are sold by Sigma-Aldrich.
Search Sigma-Aldrich web-shop for "glindemann" or enter Sigma-Aldrich catalogue number

Please contact Dr. Glindemann at dglinde@aol.com if you currently experience ordering problems.

Carl Roth GmbH,
link to 28 European countries
 

9.011 664

 9.011 668

Address

Lab Logistics (Quadrolab) in UK, Irleand
AJ Cope & Son Ltd 

click link

24 Windorah St, Stafford, Brisbane, Queensland, 4053, Australia

Ph: ++61(0)7-3356 8199
Fx ++61(0)7-3356 6722
labglass@gil.com.au

480, rue de Châtelet B- 6010 Charleroi, Belgium

Ricanska 10, CZ-10100 Praha 10

click link

3, rue de la Chapelle/B.P. 11, F-67630 Lauterbourg, France

42, rue Ambroise Croizat, BP 307, F-38434 Echirolles Cedex, France

Im Heiligen Feld 17 58239 Schwerte

Ph++49 (0)2304 / 932-800
Fx++49(0)2304 / 932-957

John Deere Str. 5,
D-76646 Bruchsal, Germany

Ph++49 (0)7251/717-0
Fx++49 (0)7251/717-182

Postfach 1416
D-37004 Göttingen, Germany

Ph++49(0)2225-948690,
Fx ++49(0)2225-948691

Schoemperlenstr. 3, D-76185 Karlsruhe, Germany

Ph++49 (0)721/5606-0,
Fx++49 (0)721/5606149

24 Windorah St, Stafford, Brisbane, Queensland, 4053, Australia

Ph: ++61(0)7-3356 8199
Fx ++61(0)7-3356 6722

Geismet 11, CH-4317 Wegenstetten AG, Switzerland

Phone: 1-973-467-6511,
Fax: 1-973-376-1546

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Delivery:
For taper joint sizes from 7 to 70 mm diameter.
1 unit of delivery = 50 sealing rings stored on a tube or cone matching the diameter of the male joint part, in a labeled bag including information in several languages:

                  
                                   50 rings on a storage tube
Foto:
50 PTFE rings
on a plastic storage tube
fitting joint 29 mm.

Retail-Prices in Europe: 1 unit of delivery (50 rings) about 25...35 EURO (ask your trader).

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Procedure:
Slip a sealing ring onto the male part of the joint. The ring adheres by elastic tension. One ring is normally enough. Two rings with about 3 mm distance. Make sure that the ring is not twisted.

Delivery: 50 sealing rings on a tube, matching the diameter of the male joint part.

The sealing ring looks on good joints "tightly" like grease.

Gently press the glass parts together. The ring must look transparently "tight" all around. Do not break the joint by overstressing. For less smooth glass joints a miniscale amount of grease should be used. The parts of the joint can also be rotated and rubbed to produce microscopic PTFE-filings which smooth the glass.

The sealing ring becoming "visibly" tight
On the left: Ring before pressing the 2 joint parts together

Centre: Ring after pressing - transparently like grease. Under pressure the PTFE, although free of grease, flows like grease into the uneven surface of the ground joint

On the right: Compared to a greased joint, equally transparent. But grease is not solvent resistant and not very clean.

Disconnect the joint by moving one part of the joint back and forth (do not pull). With 2 rings extra motion.

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Frequently asked questions and Know How on PTFE sealing rings for Taper Joints

QUESTION: Ordering. Where can I order these PTFE sealing rings? ANSWER: Search the list of traders at this homepage. If your home trader is not on the list ask him to manage to buy sealing rings from one of the listed traders for you.

QUESTION: Sizes. Are sealing rings available for all joint sizes? ANSWER: Yes. Rings are available for 5...70 mm taper diameter.

QUESTION: What is the price of these PTFE sealing rings?
ANSWER: The price is in Europe about 25 Euro per unit of delivery (50 rings). So one ring is about 0,50 Euro.

QUESTION: How does the PTFE ring seal work?
ANSWER: The plastic PTFE (known as Teflon) of the sealing ring acts similar to joint grease. But PTFE is much more clean and chemicly inert than joint grease. The PTFE flows under  high pressure slowly like grease or wax into the uneven spots of the ground glass surface. By this cold flow the free leakage volume between the 2 joint parts is filled and sealed by PTFE. PTFE is in fact much harder than grease or wax. To make PTFE flowing like grease it must be under a very high pressure. This pressure is produced by pressing the 2 glass joint parts together. But the force to produce this pressure is applied to the PTFE and the glass as well. This force can break the female part of the glass joint by tensile stress. But the glass is of course not allowed to break ever. Therefore, the PTFE ring is shaped to contact the surface of the ground joint only at a very small area (just the area of the 0,6 mm wide ring). If you force the 2 glass joint part together they contact each other only via the small PTFE ring. This relatively small force results therefore in a comparatively large deformation pressure on the PTFE. With this theory on PTFE ring seals in mind you can use the following rules to use these rings more efficient: Any factor which makes the PTFE more soft makes the seal better (high temperature, presence of traces of plasticizers, solvents, water, grease). Any factor which makes the ground glass surface more smooth makes the seal better (polishing of the glass surface). Any factors which gives the PTFE more time to flow makes the seal better (usually the final sealing is better a few hours after pressing the joint together).

QUESTION: I have doubts that PTFE can seal a glass joint properly. I used PTFE-sleeves and found they have no sealing properties compared to a bare glass joint.
ANSWER: The common PTFE sleeves which do not have sealing ribs have in fact no sealing effect because they do not work like PTFE rings. PTFE sleeves cover the whole joint. Therefore, the pressure on sleeves is too low to make the PTFE flowing like grease.

QUESTION: Sealing Containers. Can I use the PTFE sealing rings to seal containers with glass taper stoppers? (Reagent tubes, flasks, erlenmeyer flasks, bottles)
ANSWER: Definitely, this works great. You fill find, that the PTFE sealing ring will make the glass stopper fixed in the container. Therefore, a slight overpressure in the bottle will not push out the glass stopper. To loosen the glass stopper, do not pull the joint parts apart because this needs too much strength. Instead, move the stopper to and from several times or rotate one joint part.

QUESTION: I can not remove the stopper with a sealing ring from the joint or bottle. Why are the glass joint parts with a sealing ring stuck if I try to pull them apart?
ANSWER: Do not pull the joint parts apart because this needs too much strength. Instead, move the stopper to and from several times or rotate one joint part.

QUESTION: Can I use the ring more than one time?
ANSWER: Yes. The ring can be removed from one joint and can be transfered to another joint. But scratches and dirt can make it less tight over the time.

QUESTION: How can I remove the PTFE sealing ring from the glass joint?
ANSWER: Just slip it off. The PTFE rings adheres to the male glass joint just by elastic tension, which prevents the PTFE ring from falling of the male glass joint.

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QUESTION: Extra tight seal. I used a PTFE ring seal and found the sealing not proper enough.
ANSWER:
Inspect the seal if it looks transparently "tight" all around the joint. If there are "bad" looking spots (one millimeter is enough to cause leakage) then the ring is probably scratched or dented.
Some times the surface of the ground joint is simply to rough to fit the PTFE ring seal.
There are different possibilities to smooth out the roughness of ground jointed glass ware.
The joint with a PTFE ring seal can be rotated and rubbed to produce microscopic PTFE-particles which smooth the glass at the PTFE-contact zone forever. This zone of the joint looks like greased but it is in fact a layer of small PTFE particles which fill out the uneveness of the ground glass. To make the smooth contact zone broader move the PTFE ring on the joint and rotate the joint parts again. Remove larger visible PTFE-fibres after this procedure. The PTFE-ring used for rubbing has to be sacrificed often because it looses larger PTFE-particles which make the ring uneven.

Foto:
Extra tight seal.
Smooth a 2 mm zone of the male glass joint with PTFE filings from a ring by rubbing. Sacrifice this ring used for rubbing. Slip a new PTFE Ring onto the smoothed zone. This extra smoothing will result in an almost hermetic extra tight seal.
But you can of course use PTFE sealing rings without this procedure, for most purposes.

Another possibility is to soften the PTFE sealing ring.  This can be performed by applying a micro scale amount of grease or solvent or water.Do not clean your jointed glass in Potassium Hydroxide solution which makes ground glass even more rough. You can also ask your glass blower for slightly polishing the joints. A simple home made fire polishing procedure is to direct a very hot welding flame (more than 2000^oC) for a few seconds (do not deform the joint) directly around the grounded glass surface.
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QUESTION: Extra clean work: How can I extra clean the PTFE ring for ultra clean work (biochemical, pharmaceutical, analytical, organometal work) ?
ANSWER: You can either bake the ring or you can extract contamination with solvents.
Baking: The PTFE ring can be baked at 300 oC in an oven. But do NOT put the plastic storage tube at heat over 100 ^oC! Slip the PTFE ring on a male glass taper stopper to prevent it from shrinking .
Solvent extraction: You can bathe, purge or rinse the PTFE rings with any useful solvent (PTFE takes any organic solvent). You can also put many PTFE sealing rings alltogether in a Soxhlet Extractor and rinse them with the solvent, which has a boiling temperature below 70 ^oC (at higher temperature, the rings will start to shrink).
Take care, that this cleaning (baking or solvent rinsing) will make the PTFE less soft and reduce the sealing power slightly. If you want to soften the PTFE ring again, you can add a micro amount of any greasy, oily or slippery chemical  which does not harm your laboratory work.

QUESTION: How can I prevent that the sealing ring teared up and fell off   the joint after baking/heating over 200 ^oC?
ANSWER: Slip the ring before heating on the thinner part of the taper joint.

QUESTION: I took the ring off the joint and it contracted to be too small to install it again on a taper joint.
ANSWER: You can stretch the ring  to fit again the joint. Stretch the ring with a storage cone which you bought together with the rings from your trader. You can also use two fingers, sticks, nails etc.
Foto:
Sealing ring contracts (shrinks)
if removed from the joint.

QUESTION: The sealing ring became to large in diameter and fell off the joint.
ANSWER: The diameter of the ring can be decreased by use of high temperature of 100...300 oC (oven, lighter, Bunsen burner).

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1. Test report of GLINDEMANN-PTFE-sealing rings for ground tapered joints
from: Dr. Andreas Bolte, Group Prof. Dr. Borislav Bogdanivic, Max-Planck-Institute of Coal-Research, Germany
Dear Dr. Glindemann:
Our inorganic and organometallic laboratory research needs often absolute clean and tight sealing of tapered joints on glass equipment.
Your PTFE-sealing rings proved to be a success while:
long term sealing of high vacuum equipment,
long term sealing of inert equipment until 200^oC,
sealing of equipment and containers for synthesis and storage of dangerous (inflammable in air), oxygen sensitive and moisture sensitive chemicals,
sealing of equipment where contamination of reaction mixtures by joint grease has to be avoided.
Our group has gone over to use Glindemann-sealing rings instead of joint grease or PTFE-sleeves because of the amazing sealing properties and the advantages of working with greaseless joints.
(some extended information in the German version is not translated here)
We consider your PTFE-sealing rings as the present most advantageous way to work with greaseless and tight joints.
(signed by Andreas Bolte)

2. Test report of GLINDEMANN-PTFE-sealing rings for ground tapered joints
from: Professor Michael D. Fryzuk, Department of Chemistry, University of British Columbia, Canada
Dear Dr. Glindemann:
Thank you for the sample of your amazing o-ring seals. We have used Teflon sleeves in the past for certain situations but we have discontinued this practice because they are too expensive and not particularly effective. We have tested your o-ring seals using an extremely air-sensitive solution of {Co₂TiCl}₂ZnCl₂ in toluene. This material is our indicator for O₂ in our inert-atmosphere glove boxes since it goes from deep blue green to bright orange in the presence of 5 ppm of O₂. A tube with 3 mL of this deep blue green solution was sealed with a stopper that had one of your seals and no grease inside an inert atmospheres glove box; the tube was then removed to the outside and inverted so that the solution was on top of the stopper. The colour could be seen to penetrate to the o-ring seal and no further. And amazingly, the solution remained blue green for many days. This tells me convincingly that this seal is airtight and robust. I would buy such a product because it is ideal for our research on air- and moisture-sensitive organometallic complex compounds.
Sincerely,
M. D. Fryzuk
for <dglinde@chem.ubc.ca>; Tue, 10 Mar 1998 08:47:40 -0800

3. Test report of GLINDEMANN-PTFE-sealing rings.
from: Fan Ouyang, Beijing University of Aeronautics and Astronautics, April 24, 2003
My name is Fan Ouyang. I am a senior undergraduate at Beijing University of Aeronautics and Astronautics. I am now engaging in a new compound synthesis.
In our synthetic chain, there was a key link that should be reacted at high temperature (>110℃) and high pressure (>8 Bar) for 12 hours. To realize the condition, we designed thick-wall glass tube to bear the high pressure, but in practice, we found the standard conical joints could not meet our hermetic requirement that a low-boiling-point reagent (5 ml) leaked completely in less than one hour.
Fortunately, in a journal, we saw the Glindemann-Sealing Ring. These sealing rings were designed for standarded conical joints that they are available for all joint calibers: NS 7,10,12,14,19,24,29,34,45,50,60,70.
We used the 19-sized sealing-ring. As it was described at the references, the sealing ring was very effective. Not only could it be used under high temperature, but also after 12 hours reaction with the high air pressure, the low-boiling-point reagent leakage rate was less than 10% (0.5ml/5ml).
Thanks to the Glindemann sealing-ring, our experiment finally got a complete success.
So I am glad to introduce this effective and convenient ring to my dear colleagues in China. Besides their excellent hermetic and vast application conditions, they can conveniently change a common joint into a hermetic joint so that it can save the investment on specialized equipment.
我叫欧阳凡，现在是北京航空航天大学大四学生。我现在正在合成一种新型化合物。在我们的合成路线中，有一个非常关键的步骤，需要在高温（>110℃）高压（>8个大气压）条件下反应12小时。 为达到这一目的，我们设计了厚壁的玻璃仪器来承受高压， 但是在实际操作中，我们发现标准磨口在我们的实验条件下不能达到要求的密封程度，一种低沸点的反应物（5ml）会在不到一小时完全泄漏。很幸运，在一本杂志上，我们发现了Glindemann密封环的广告。这种密封环是专门为标准磨口设计，型号有7、10、12、14、19、24、29、34、45、50、60、70，可以应用于各种磨口。抱着试一试的心态，我们使用了19口的密封环。正如其产品说明中介绍的一样，这种密封环非常有效。其不但可以在高温下使用，而且在> 8个大气压的气压下反应十二小时后， 低沸点的反应物泄漏不超过10%（0.5ml/5ml）。在这种密封环的帮助下，我们的实验最终取得了成功。 因此我很乐意向大家推荐这种密封环。 除了其优异的密封性能和广泛的使用条件，其最大的优点就是可以方便的使普通标准磨口达到很好的密封性，可以节约专门的密封设备的投资。这尤其适合中国的国情。