Depending on your application, you need to choose the right Cords and materials.
In power transmission, it's mainly a matter of turning fast on small pulleys, at constant speed. In conveying, products are transported at slow speeds over the back of the Belt. The stresses on the Belt are therefore very different.
Power transmission
Poly Chain® driving belts are designed for high-torque, low-speed transmissions. The carbon-fiber reinforcement of these belts provides dimensional stability, ensuring perfect meshing of the belt with the Pulley.
Synchronous belts in Polyurethane ensure excellent tooth strength and abrasion resistance. The best thermal resistance of power transmission belts is provided by Poly Chain® belts in Polyurethane, which can withstand temperatures ranging from -54°C to 140°C, compared with -20°C to 100°C for Neoprene driving belts. The Neoprene driving belt offers very high fatigue strength (Neoprene being a softer, more flexible material than PU). On the other hand, the abrasion resistance of a neoprene belt will be more moderate than that of a polyurethane belt.
The specific construction of Synchronous belts in Polyurethane offers superb resistance to oils, acids and chlorine. The most fire-resistant belt is Poly Chain®.
Transport
Polyurethane conveyor belts offer the same technical characteristics as belts (sleeves) made from the same material.
| Materials | Neoprene | PU (Manchons) | PU (Poly Chain®) | PU |
|---|---|---|---|---|
| T°C | -20 to 100°C | -5 to 70°C | -54 to 140°C | -5 to 70°C |
| Oil resistance | Average | Excellent | Good | Excellent |
| Acid resistance | Low | Good | Very good | Good |
| UV resistance | Good | Low | Good | Low |
| Fire resistance | Very good | Good | Excellent | Good |
| Chlorine resistance | Low | Good | Very good | Good |
| Fatigue strength (bending) | Excellent | Very good | Good | Very good |
| Hardness | Average | High | Maximum | High |
| Mechanical strength of the tooth | Good | Very good | Excellent | Very good |
| Abrasion resistance | Average | Good | Excellent | Very good |
Timing belt Cords
There are 4 types of Cords in driving belts: Fiberglass - Steel - Kevlar® or Aramid and Carbon.
Steel cords offer excellent tensile strength and very low elongation compared to fiberglass cords. Fiberglass Cords, on the other hand, offer excellent fatigue strength and moisture resistance, as do Carbon tensile ropes.
| Materials | Fiberglass | Steel | Kevlar® | Carbon | HF steel |
|---|---|---|---|---|---|
| Traction resistance | Average | Excellent | Good | Very good | Very good |
| Fatigue resistance | Excellent | Average | Average | Good | Good |
| Humidity resistance | Very good | Average | Good | Very good | Average |
| Ø min | Very good | Average | Average | Good | Good |
| Pinch resistance | Average | Low | Low | Low | Low |
| Relaxation | Average | Excellent | Averageoyen | Very good | Excellent |
| Stability over time (elongation) | Average | Excellent | Average | Very good | Excellent |
| Stiffness | Low | High | Good | Very good | High |
ANSWERS TO YOUR QUESTIONS ABOUT TOOTHED BELTS
When should I use a Belt with Kevlar® rather than steel Cords?
There are a number of criteria for choosing to use Kevlar® instead of steel:
- Use of a metal detector close to the Belt
- A large number of applications in the agri-food sector use Kevlar® rather than steel
- Kevlar® does not deteriorate in damp conditions
- At high speeds, Kevlar® will not generate electrical interference
Why use a polyurethane Timing belt instead of another type of timing belt?
Polyurethanes have unrivalled abrasion resistance compared with other plastics. Polyurethane will not shed particles during abrasion, which could contaminate essential components of the product or the environment.
Polyurethanes are highly elastic and resilient, which helps them absorb shocks.
Polyurethanes can maintain flexibility over a significant temperature range (from -30°C to 80°C; short-term to 120°C). Polyurethane does not harden or degrade as quickly as neoprene.
In what chemical environments can polyurethane belts be used?
Polyurethanes are generally resistant to ozone, hydrocarbons, greases, oils and ambient temperatures. Belts are generally attacked by concentrated acids, chlorinated compounds, hydrocarbons and high-temperature water. Certain chemicals known to attack polyurethane may be used with PU belts, depending on the relative concentration, temperature and duration of chemical exposure. We are unable to control the environment under which a belt is used, so it is up to the customer to determine the suitability of the belt under these exact conditions.
Why use nylon on the tooth or back of the belt?
Neoprene belts use a nylon fabric on the tooth of the belt to improve tooth shear strength, promote sliding during meshing, and increase abrasion resistance.
Nylon on the teeth is used on a polyurethane belt to reduce the belt's coefficient of friction for conveying and, in some cases, to reduce the noise generated between the belt and the pulley in a relatively high-speed application.
Nylon on the back of the polyurethane belt is used to reduce the coefficient of friction in cases where the product must slide on the back of the belt, or for other applications where low friction is desirable on the back of the belt.