Tag Archives: PTFE

PTFE Coated Fiberglass: Sintered versus Unsintered

Posted on by W.F. Lake Corp.

The definition of “Sinter” is: “To make a powder coalesce into a solid or porous mass by heating it without liquification”.  We typically think of sintering as it relates to metal (like bronze or brass).

W.F. Lake Corp. manufactures both sintered and unsintered materials.  With sintered PTFE, we essentially have taken a PTFE powder dispersed in water and fused it using heat into a hard, slippery coating that operates at very high temperatures, is chemical resistant and very few things stick to.  These are sintered PTFE coated fiberglass products.  Unsintered products are essentially an impregnated coating of PTFE that is dried in place, but not fully fused. It has a “waxy” feel and is less abrasion resistant.

Why sintered?  Sintered PTFE coated fiberglass fabrics, tapes, belts and sewing threads are the typical form of PTFE coated textiles you see in the marketplace.  They are the work-horse products for food processing (belts and sheets), packaging (L-Sealer bars), molding (composite release sheets), flu-gas filtration (PTFE coated fiberglass sewing threads), high temperature, hot face insulation (S-2 glass, Quartz sewing threads, etc…), and many other applications.  In these cases, PTFE powder suspended in water is fused at high temperatures (sintered) to form a solid PTFE coating.

Why Unsintered?  We are unique in that we also coat many of our fiberglass yarns with unsintered PTFE.  This process requires precise temperature control to essentially “bake” the PTFE particles without fusing them together.  This leaves a waxy type coating that has both penetrated the fiber bundle and leaves a portion of the coating on the surface of the yarn. In most cases, these yarns are braided over wire conductors or made into lacing tapes and tie cords. The advantage an unsintered PTFE coating is that it allows for further processing and bonding of subsequent layers of PTFE; in the form of PTFE films, coated fiberglass fabrics or even additional PTFE dispersions.  When all of these are finally fused, or sintered, our customers form a homogeneous coating that very effectively resists chemicals, operates at high temperatures, will not burn or support flame, will not rot or support fungus and provides excellent electrical insulation.

Most of us use sintered PTFE products virtually every day.  Pots and pans, baking sheets, even breathable, water repellent rain ware (and sometimes vascular grafts!).  Unsintered PTFE products in daily use are less prevalent, but are available as Thread Seal Tape (unsintered PTFE film), packing (valve stems, shaft logs) and gaskets (valve stems), etc…  PTFE is an amazing material.  Give us a call with any questions or application opportunities… we’re here to help!

PTFE Coated Fiberglass Lacing Tapes and Tie Cords

Posted on by W.F. Lake Corp.

W.F. Lake Corp. manufactures a wide range of PTFE coated fiberglass lacing tapes and tie cords that meet a number of military and commercial specifications.  These products are amazing in their long term performance characteristics.  Once installed, they rarely, if ever, need attention…no one wants to open up an airframe for a failed “zip tie”!  Unlike plastic zip ties, our products will not burn or support flame, will not rot or support fungus, are unaffected by virtually any chemicals including aviation fuels, diesel fuel, gasoline, oil, hydraulic fluids, etc.  They are unaffected by UV light and are highly flexible due to the nature of the PTFE coating and braiding process used in their production.

Of course, a “Lacing Tape” is a flat braid, while a “Tie Cord” is a round braid.

W.F. Lake Corp. puts extra effort into our lacing tapes and tie cords by first coating each fiberglass yarn with PTFE prior to the braiding process. This extra step of glass impregnation before braiding acts as protection against fiber-to-fiber abrasion during fatigue.  Also, when high local stresses occur, the PTFE coating allows mechanical transmission of the load within the lacing tape or tie cord to maximize load sharing between the fibers.  Typically, the PTFE coating represents 15% of the overall braided cord.

Some of our PTFE coated fiberglass lacing tapes and tie cords have been tested for outgassing properties by NASA (contact the factory for the location of this information).  Many of our products are also designed to meet military and commercial specifications including:

Military Specifications:

 

Marshall Space Flight Center

 

When it comes to high performance braided lacing tapes and tie cords, think of W.F. Lake Corp.!

 

Belt Repair 101…a how-to and guide for fixing your damaged belt

Posted on by W.F. Lake Corp.
23 Mar

Can I repair my Teflon* coated fiberglass screen print dryer belt in the field? We often get that question. As usual, the answer depends on the damage done and the amount of wear the belt has experienced.

W.F. Lake Corp. has been manufacturing these belts for quite some time, and we’ve seen some pretty creative repairs made…literally duct tape and bailing wire (but no bubblegum yet)! Truthfully, screen printers are a creative bunch (kinda’ have to be, right?) and often make repairs using whatever is lying around the shop.

We’ve seen ragged cuts from carts that bumped against a running belt; burnt areas created when a belt stopped and sat too close to an IR heater; cuts made when unboxing a new belt; torn edge trim when a belt tracked off the pulleys; broken splices from over-tensioning, etc.  And, of course, lots of belts that are just worn out.

So, can I fix it myself? If it involves simply patching a small hole or sewing on a piece of edge trim, the answer is yes. Use one of our repair kits to put it back into service. If the metal lacing pulled out, give us a call to discuss your options.  If, however, the damage is severe or it is a pulled or torn splice, it probably cannot be fixed in the field but we may be able repair it at the factory. And if the belt is just plain worn out, we usually suggest a new one since the required thermal welding bonds are inhibited by dried inks that may have penetrated the coating.

Whatever the cause, we’re always willing to help out to see if it can be fixed, either in the field using one of our repair kits or sent back to us for investigation / factory reconditioning. It’s worth noting that some customers purchase a new belt and then return their old belt for review to see if it can be repaired and used as an “emergency backup” belt.

The operating characteristics of PTFE coated fiberglass belts are pretty impressive and if care is taken, these belts last a long time. Give us a call, e-mail us a question or ask for a quote out of curiosity. Check out how to measure a belt for the most easy and accurate way to give us the dimensions you need…each of our belts is custom made to your specifications!

Note: Before starting a new Teflon* coated fiberglass screen print dryer belt, be sure to check out our Belt Startup & Operation data.

*Reg. Chemours

Color of PTFE Coated Fiberglass Fabrics, Tapes, and Belts

Posted on by W.F. Lake Corp.
12 Apr

PTFE Coated fiberglass fabrics, tapes and belts are typically a tan color.  Within the industry, we call this color “Natural”. But if you’ve ever worked with fiberglass fabric (maybe to repair your car or boat), it looks white. And of course it is white until it sees heat, then it turns “tan” or “natural”. Read on if you’d like to find out why!

Fiberglass yarns are made up of very fine filaments of glass fiber. These filaments are amazing little things, but they are, after all, glass and are subject to damage or breakage like any glass product would be.

Imagine very fine fiberglass rods; they’d easily snap and break if not handled very carefully. In order to make fiberglass filaments more durable, a starch “binder” is applied to the filaments to protect them in further handling, braiding, twisting, weaving, etc. These binders are organic… in some cases they are potato starch!

These binders caramelize when they see heat, very similar to a piece of toast turning brown in your toaster! Of course, PTFE coating of fabrics, tapes and belts requires relatively high temperatures to cure the PTFE. That tan color from the binders being heated is then trapped within a translucent PTFE coating, thus making the final product “tan” in color.  We call it “natural” because it is what naturally happens to these binders. You may see slight variations in the tan/natural color of the product because different binders are used on different yarns.

OK, but why are some black in color? That’s because we sometimes add pigment to the PTFE dispersion to achieve different colors or characteristics. Black is often used for several reasons. First and foremost, it is used to pigment belts in ultraviolet curing ovens (most often in the screen printing industry). When under UV lights, the starch binders that make a fabric or belt “tan” will bleach out, turning your tan belt a funny shade of off-white.

Although this in no way impacts the performance of the belt, it is often perceived as a failure. In order to hide that change, we make the belts black. That same black color can mask other things like wicking oils in food processing, ink from screen printers, etc. In some rare cases, specialized pigments (mostly black) are used to try to impart a degree of conductivity to this incredible insulator. In most cases, the point is to create a path to discharge static electricity.

What about other colors? Sure, they can be done but really are very specific to certain industries and not typically an issue in most commercial applications.

Yarns for electrical insulation are an entirely different beast, Yes, we manufacture those as well, but they are another topic entirely!

Again, and as always, contact us with any questions or comments. We’re here to help!

Helpful Tips for Sewing with PTFE Coated Fiberglass Threads (and other high temperature threads)

Posted on by W.F. Lake Corp.
18 Mar

PTFE Coated Fiberglass, PTFE Coated S-2 glass, PTFE coated Quartz and other high temperature, composite sewing threads offer amazing operating characteristics. Unaffected by most chemicals, they will not burn, will not support flame, will not rot or support fungus. Our PTFE coated quartz thread operates to 2,000 deg. F. Amazing! However, you wouldn’t use these threads unless you have to, not necessarily because they’re overly expensive, but because they require a special skill set in order to make them work. If your application needs these properties, however, there are no alternatives. I like to say this is OK because it prevents everyone with a sewing machine in their garage from becoming your competitor! It’s not as easy as changing a bobbin and switching from polyester to S-2 fiberglass with Inconel wire twisted into the thread!

As mentioned, this is not a drop-in substitute for an aramid, polyester, or any other thread. There is a learning curve to go through if unfamiliar with this type of thread. The very unique and extreme operating properties of PTFE coated fiberglass (or S-2 glass, Quartz, wire inserted, etc.) threads require operator training and machine adjustments to make them work acceptably.

First of all, a factory lubricated thread is going to be much easier to use. This lubricant is applied after PTFE coating. We offer two high speed thread lubricants. X80 is a silicone/mineral oil based thread lubricant and is, by far, the most popular choice. This product is ideally suited for extreme needle heat environments when sewing through multiple layers of thermal insulation, like silica blankets, ceramic fiber mats, texturized glass, etc… We also offer a wax based thread lubricant (X50) that is used occasionally for lighter duty applications. In a few cases, customers will “post bake” the final product to remove any residual oils.

With or without the use of lubricants, the following suggestions help dramatically.

SLOW DOWN. Especially if un-lubricated thread is being used.

Change all hooks, needles, tension guides, etc. Anything that touches the thread must be free of burrs, gouges, etc. These items will need to be changed regularly.

Be sure the tension device where the thread comes out of the bobbin case is new and burr-free.

Use the correct needle size. We’re happy to help out with a suggestion.

Be sure there are no grooves where the thread passes through the hole in the walking foot. No rubbing or abrasion points.

If sewing with a wire inserted (Stainless steel, Inconel or other), try placing a nylon stocking over the thread spool and pass the thread through a hole in the top of the stocking. This helps prevent free-spooling of the thread and minimizes any “kinking” due to the steel or wire insert.

There will likely still be breaks occurring, but the properties of these threads are outstanding and we must sometimes put these difficulties in order to take advantage of these amazing products.

As always, let us know if you have any questions or comments.