In a previous article, we discussed how cores are generally priced. Nylon is cheaper than polyester, which is cheaper than Kevlar. This then begs to question, what is the difference between them? Which one is right for you? In this article, we are going to discuss and compare the common cores that are found in transmission belts.
Nylon
This is a very flexible material with a standard elongation of 1-2%. When it comes to splicing the belt, nylon core belts are generally spliced skive style. This means that you have to grind the belt properly (we will cover this in a later video) and apply the appropriate bonds onto the belt. Each brand is different but generally there is one bond that goes onto the nylon and another that goes onto the rubber. Nylon core belts are resistant to the following materials; oil, ozone exposure, steam, fat, benzine, and cracking due to wetting and drying. However, these belts are not resistant to; acids (organic and inorganic), phenols, ketones, and alcohols. There are a lot of applications when it comes to these kinds of belts. In paper manufacturing and converting alone they can be used on; tissue and tube winders, envelope machines, printing, cutters, unwinds and rewinds. Nylon core belts can also be used on textile machines, live rollers, corrugated/folder-gluer machines, mail processing, roll stands on flour milling, and wood working equipment.
Polyester
This is a very dimensional stable material with a standard elongation rate of 1%. This sort of material is used in high speed, medium-extreme duty applications. In these applications, polyester shows resistance to humidity and friction. Unlike the nylon cores, polyester belts are finger spliced. Which provides the core with several advantages. First off, there is an ease of joining due to the fact that there are no adhesives being used. This kind of splicing also requires little experience. A single action cutter will cut the fingers to the proper size to where they can then just be cooked onto the machine. Lastly, the finger splicing leaves a smooth splice that does not catch paper when running. Polyester core belts belts are used across several industries. First, they are used on the press folder and stream feeder deliveries in binderies. Secondly, they are used on corrugated, folder-gluer, and multiwall bag machines in the paper manufacturing and converting industries. Lastly, they are used on a lot of machines in the mail processing industries.
Kevlar
Kevlar cores have a lot of the same properties as polyester. It too is a dimensionally material however, it has a standard elongation rate of .05%. It is also a higher strength material that has constant tension, spindle speeds, and a longer life. Kevlar core belts are resistant to oil, temperature, humidity, and friction. They are also used in a lot of the same industries that polyester and nylon are used in. Kevlar is also finger spliced like polyester which means that it possesses all of the same benefits.
Conclusion
All of these belts are generally used within the same industries across the board. With that being said, they are all resistant to a lot of the same things (oil, temperature, and humidity). However, Kevlar and polyester are going to be more resistant to friction than nylon is. On the other hand though, nylon is going to show a better resistance to flexing fatigue. Another big difference is the splicing. Nylon requires skive splicing with adhesives which generally requires training. Finger splicing is a much easier process that requires no adhesives or training. These cores all also have different strengths and elongations rates. A good rule of thumb is that the stronger the core, the less that the belt is going to stretch. Lastly, another trend is that Kevlar has a lot of the same properties as polyester, however it is just a stronger longer lasting material.