Processing of Thermoplastic Copolyester Elastomers

Thermoplastic polyester elastomers are class of engineering materials which combine elasticity of conventional vulcanized rubbers with processing efficiency of thermoplastics. Commercial grades of TPEEs are available in the range of Shore D hardness values from 32D to 82D. Some special grades contain UV stabilizer, heat stabilizer, flame retardant or hydrolysis resistant additives. They are processed by most conventional techniques, such as extrusion. 

The TPEEs are slightly hydroscopic due to their polar character. They are resistant to hydrolysis under ordinary conditions, but moisture content should be lower that 0.1 wt %. The presence of moisture in the polymer could cause degradation during processing. Most of TPEEs are supplied in moisture-proof containers, therefore the 

Extrusion. For processing of TPEEs by extrusion, the single-screw machines are recommended. The screws should have hardened surfaces for good wear resistance. A general purpose extruder barrels may be used with preferable length to diameter (L/D) ratio 24/1 to provide the best melt quality for precision extrusion. The barrel should have at least four independently controlled heating zones. Compression ratios should be between 2.5/1 and 3.5/1, as determined by the depth of the feed zone divided by the depth of the metering zone channel. 

Melt Casting. Melt casting is a process that combines elements of both extrusion and injection molding. Conventional plastic extruders with ax nozzle head are used to deliver melt to a vented mold. TPEEs are suitable for melt casting owing to their relatively low melt viscosity. The molds for melt casting are inexpensive, and the products of complex shape could be easily manufactured. The 

The TPEEs resistance to oil and chemicals, together with their flexibility and abrasion resistance, make them suitable for application in many types of cable jacketing and hose, both as tubes and covers. Taking advantage of their mechanical strength combined with environmental resistance, TPEEs can be used in the fiber optics technology for cable jackets. 

---