Thermoplastic polyester elastomers (TPE) became available to consumers in the late 1970s. This type of plastic has a great advantage over other materials as it can stretch to moderate elongations and return to near its original shape, and be processed as a melt at an elevated temperature with little to no significant creep. Hytrel® is the registered trademark name for the DuPont™ brand of TPE. It combines many desirable characteristics of this high-performance elastomer. Such as an excellent flex fatigue rating, broad temperature use, resistance to tearing, flex cut growth and abrasion, resistance to hydrocarbons and many other fluids, while being available in a full range of Shore D hardness.
It is an all-in-one thermoplastic and elastomer
Hytrel® provides the flexibility of rubbers with the strength of plastic. Its excellent crossover properties allow it to be used for any number of applications. Especially those applications where durability and mechanical strength are required for a flexible product, such as seals, belts, bushings, diaphragms, etc. With Hytrel®, parts that previously required multiple composite assemblies can now be made with a single material.
Hytrel® has a great ability to resist permanent deterioration over numerous stress cycles. As a piece of material is flexed and relaxed it begins to deteriorate due to thermal and mechanical stresses. Flex Fatigue is measured by using a fixed cantilevered system capable of producing a highly repeatable force on a test specimen. The force is repeated again and again and counted, when the material fails, the number of cycles is measured to determine its flex fatigue characteristic.
Broad Temperature Uses
Hytrel® polymers have outstanding thermal properties, especially with respect to material stability. The melt of the product under normal conditions produces almost no gas by-products. The stability of Hytrel®’s chemically pure polymer, with no additional plasticizers, minimizes viscosity issues during injection processes.
Tear resistance with flex cut growth and abrasion
Hytrel® combines a crystalline phase – thermoplastic matrix, which makes it rubbery, with an amorphous phase, elastomeric characteristic. By varying the percentage of each phase within the recipe, Hytrel® can be made to be very resistant to specific physical stresses, such as tearing, flex cut growth and abrasion.
Resistance to hydrocarbons and many other fluids
Hytrel® is highly resistant to non-polar materials, such as toluene, gasoline, and other hydrocarbons. This resistance is excellent even at elevated temperatures. However, polar materials, such as water and Hydrogen and Hydrogen Sulfide, will have severe effects on Hytrel® at elevated temperatures. Generally speaking, the stiffer the grade of Hytrel®, the more fluid resistant it becomes. It is important to predetermine the environment within which the Hytrel® will be used. Higher temperature more chemically resistant Hytrel® variants are usually the hardest or stiffest grades, whereas softer Hytrel® variants usually work better in low-temperature environments.
Shore D Hardness
The Shore D (Durometer) Hardness Scale is a measure of the hardness of hard rubbers and elastomers, as well as softer plastics. Hytrel®’s versatility is due in part to is availability in a wide range of Shore D Hardness ratings. The Shore D Hardness method is used to determine the material’s resistance to indentations and provides empirical hardness values. The Shore D hardness scale covers materials as soft as auto radiator hoses to as hard as kitchen laminate counters. However, these values do not correlate with other fundamental characteristics of the material so are useful for unique instances only. There are other scales that measure hardness for different materials and blends, like the Shore A Scale. There is some overlap between these scales, for example, material that measures 45D on one scale will measure 95A on the other. However, direct correlations between scales are unreliable.
Hytrel® is ideal for fixed belt drive applications:
One application in the belt industry for which it is ideal is that of fixed center drives. A fixed center drive is an option for production or assembly belt drive system. Its main attributes are its simplicity and its reduced hardware expense and component requirements.
A fixed center drive design uses a synchronous drive system due to its tooth engagement mechanism. Other belt systems may rely on friction and tension to transmit power. Hytrel® TPE is an ideal material for this type of belt drive as it can handle the extreme physical and thermal stresses of being continuously driven with little wear and deformation. Hytrel® also comes in such a large variety of materials that one form or another of it can be used in almost any belt drive.
Think Hytrel® might be right for your belt?