1. Processing Parameters
The following sections provide information and recommendations for processing ELASTRON TPE compounds. Please keep in mind that your experience with your machines and the particular material processed should always be taken into consideration as well. As ELASTRON compounds are frequently custom-developed to individual customer requirements, differences in processing can result.
Our applications engineers will be happy to provide any advice you may require and to come to your plant upon request to observe processing of sample materials.
2. Barrel and Melt Temperatures
When processing standard ELASTRON G and ELASTRON V compounds, adjust the barrel temperature such that the melt temperature is between 180° C (355° F) and 220° C (425° F) (max. 250° C (480° F)). To do this, increase barrel temperature progressively in all zones in steps of 10° C (50° F) to 20° C (65° F) starting from the hopper side until the melt temperature is in the desired range.
The temperature at the shut-off nozzle should be the same or 10° C (50° F) below the barrel temperature of the last heating zone. Overheating, i.e. thermal decomposition of the material, is easily recognized as indicated by a distinctive odour.
Exact temperature recommendations for ELASTRON standard compounds are given in the processing instructions in the table below. In the case of co-injection moulding, special procedures are required as is the case with other materials.
3. Mould Temperature
The mould temperature should normally be between 30° C and 40° C If the parts produced are thin-walled, we recommend mould temperatures between 40° C (105° F) and 60° C (140° F).
For more information on mould temperatures, e.g. for co-injection moulding with 2 or more components, please contact us.
4. Injection Pressure and Injection Rate
The cavity should normally be filled under high injection pressure and at a high injection rate to facilitate long flow paths. This applies especially if the part moulded has very low wall thickness (rule of thumb: injection rate should be in the range of approx. 100 – 200 g/s (0.22 – 0.44 lbs)).
With these parameters the optimum mould filling is set by adjusting the metering.
The dependence of flow behaviour on temperature and injection pressure is illustrated below in flow path diagrams generated by testing three ELASTRON standard compounds.
The diagrams show that the flow properties of ELASTRON compounds are far more dependent on injection pressure than on temperature.
5. Back Pressure and Screw Speed
Usually we recommend a back pressure of approximately 20 – 50 bar (285 – 710 psi). The screw speed should be between 25 and 75 rpm.
Effects of higher back pressure:
İmproves distribution e.g. of colour batches and other additives increases melt homogeneity plasticizing time is increased for a given screw speed reducing the screw speed also has a positive effect on homogeneity
Effects of lower back pressure:
Creates insufficient shear energy and inhomogeneous melt as a result, higher-melting components in the compound may not be plasticized.
6. Hold Pressure and Hold Time
The mould should be filled initially without applying hold pressure. Low hold pressure can then be applied to prevent sink marks and to guarantee 100% filling. The hold time should be set as short as possible.
Possible effects of high hold pressure:
- overfilling of cavities
- difficulties in demoulding
- de-lamination
- deformation around the sprue
- improved adhesion at flow lines
- For any further questions please contact Elastron
Possible effects of low hold pressure:
- sink marks in thick-walled parts
- increased shrinkage
* Except bondable grade
** Drying at 80ºC for 2 hours is recommended.
Note: All products can be regrinded and added 20 % to original product.