Applications and Performance Features of PTFE-Coated Fiberglass Belting
To start with, let’s frame the conversation around PTFE lightweight belting. PTFE-coated conveyor belting is a small but important segment of the lightweight belting market. It also important to note that PTFE is sometimes referred to as Teflon™, a trademark of DuPont.
PTFE belting is made from polytetrafluoroethylene (PTFE), a fluorocarbon plastic. It is a plastic in which the hydrogen normally found in association with carbon in organic materials has been replaced with fluorine. The resulting polymer possesses a number of unique properties:
- Inertness to most chemicals
- Fire resistance (will not support a flame)
- Excellent weathering resistance
- Low coefficient of friction (second only to ice)
- Superior non-stick properties
- Extreme heat and cold resistance
- Outstanding electrical insulation/dielectric properties
- Resistant to ultraviolet, infrared, microwave, and radio frequency
Where is PTFE Belting Used?
PTFE-coated fabric belting caters to a multitude of applications, but there is a short list of properties that offer the user a self-explanatory guide to the question: “Do I need a PTFE coated belt?”
If the answer to any of the following nine questions is YES, then PTFE coated belting may be right for your business.
- Is it a hot process? Most PTFE belts have a service temperature of 500° F
- Does/can the belt make direct food contact? Many PTFE-coated belts are used to cook or process foods without the use of a pan or tray. This includes COLD processing of foods as well.
- Is a non-stick (release) surface needed? Hot plastics and rubber being transported through an oven are examples of products that need a non-stick surface at the exit of the oven.
- Is the process chemically aggressive? PTFE is VERY inert. It will not react with or contaminate the product being conveyed.
- Is the oven microwave or RF heated? PTFE coated fiberglass is virtually transparent to microwave energy, RF energy, and dielectric heating.
- Is the product heated through the belt? Many solid (non-open mesh) belts slide over a heat source, such as a hot plate. The heat must pass up through the belt to reach the product. A thin belt will pass heat faster. PTFE-coated belts can be made as thin as .003 inches.
- Is the oven a hot-air-circulating oven? There are many PTFE coated open mesh belts available for ovens that require a large volume of air to pass through the belt.
- Is a low-friction surface needed? PTFE belts are very slippery.
- Does the oven use UV curing instead of heat? PTFE is very resistant to degradation by UV light.
When to Avoid PTFE Belting
Listed above are the properties that make PTFE-coated belts a good choice for a variety of different businesses, but there are also applications that are NOT well suited for PTFE belts.
Here are five applications where PTFE belting isn’t the optimal product choice:
- Abrasive applications – PTFE is a soft plastic. It will be easily damaged by transporting abrasive products such as stone, sand, etc.
- Inclined transport – The slippery surface of PTFE belting is not ideal in incline applications or environments (your products will slide right off the belt).
- Tobacco contact – PTFE is banned by most tobacco processors for any process that puts the tobacco (for smoking) in direct contact with the belt.
- Power transmission – This is a whole different type of belt. PTFE belting is a lightweight transport belt and is not applicable to this type of use.
- Gamma (radiation) sterilization of food. PTFE breaks down when exposed to gamma rays.
4 Properties that Make PTFE Belting Different
Proper application and good performance of a PTFE-coated fabric belt depends on knowing how it differs from traditional belting. These are the four important differences:
Fiberglass is the most common woven fabric used as a substrate upon which the PTFE is coated. Fiberglass is often chosen because it is economical and will readily withstand the high temperatures needed for PTFE coating. The use of fiberglass also makes the belt more fragile. Special consideration in the design of the machine must be made to prevent damage to the belt.
PTFE-coated fiberglass belts have almost zero stretch. This results in a belt that has excellent dimensional stability. The lack of stretch requires us to carefully consider how to track (guide) the belt. Crowned pulleys DO NOT WORK on PTFE coated fiberglass belts. Manually adjusting the take-up roller also DOES NOT WORK.
Tracking of smaller belts, under 4-feet wide can be accomplished with a variety of edge guide attachments to the belt. Belts over 4-feet wide and belts that move at high speeds are recommended for use with an active tracking system. A good system will have an edge sensor and a steering roll to keep the belt centered on the machine.
Most PTFE-coated fabric belts are very thin. The thickest belts in this category are about 0.040 inches thick. Some belts are as thin as .003 inches. A thin belt is desirable when the process requires thermal transfer through the thickness of the belt. A thinner belt means higher speed and higher production. The thinner the belt, the more fragile its structure becomes. As such, thin belts cannot be effectively tracked (guided) by pushing on the edge of the belt.
All PTFE-coated fiberglass belts are coated on both faces. This leads to a belt that slides easily on the machine’s support structure. The belt’s slippery surface enables the product being conveyed to slide easily and allows for simple removal from the belt at the exit of the process. The slick surface of the belt does require special attention to be given to the design of the drive roller(s) and the guiding rollers.
Selecting the correct material for the belt is only the first of three steps to a successful process. The second step is to design and fabricate the belt properly. The selection and design of the seams and edges is critical to success. There are many seam and edge selection choices—in fact, too many to list here.
The third step to a successful process is the design of the machine. A new machine design or a new process should involve the belting supplier at an early stage of process development.
Machine design factors that affect the belt include:
- Can the belt be put on endless?
- What type of seam is needed?
- How will the belt be guided (tracked)?
- How will the belt be tensioned?
- How will the belt be driven?
- How will the belt be supported?
- How will the product be put on and taken off the belt?
- How fast will the belt travel?
- What is the maximum temperature of the process?
- What is the process that happens on the belt?
The Future of PTFE Belting
PTFE-coated belting has been around for over 40 years. A lot has changed in the U.S. during those 40+ years. Some industries have flourished, while others have virtually disappeared. For example, laminators used in garment factories (called fuse presses) are almost entirely eradicated from the United States. Large dryer ovens used to process wide textile roll goods are also nearly gone (remaining one are in Asia). Fortunately, there are new processes and new incentives to use PTFE belting.
4 PTFE Belting Trends to Watch for:
- Non-garment laminators. These machines are nearly identical to the old fuse presses, but they are often bigger and process materials for automotive interiors, medical products, paper products, solar power devices, flooring, etc.
- Energy savings. Lightweight PTFE belting is being used to replace heavy metal, open mesh belts in several major industries that remain strong in the United States. Energy saving is another reason for switching from a hot (thermal) oven to a UV (light) curing oven.
- The green movement. Sustainability initiatives are creating new opportunities for PTFE belting. Recycled materials is one of several growing industries in the PTFE belting sector.
- Higher temperature processes. Applications that require higher temperatures are often needed to take advantage of new polymers. Higher oven throughput is also sometimes achieved by higher process temperatures. PTFE belting offers a higher operating temperature than any other non-metallic belt.
Contact Us Today for Further Assistance
Based on years of experience, and sampling many products, we can offer market recommendations for what suits your needs for any specified application. Contact us today to obtain samples for your evaluation!