Extrusion guide TP HFFR
This guide applies to our thermoplastic halogen free flame retardant (HFFR) products including the following grades:
TP519C, TP521, TP536, TP543, TP568, CT08-93, CT09-07, CT09-12
| Equipment | ||
| Extruder | Ideally 20 to 24 L/D ratio. | |
| Extruder head | Ideally with deep flow channels. A head assembly with a diverter valve is beneficial. | |
| Screw | Low compression less than 1.5:1 and ideally 1.2:1. | |
| Extension piece | If there is an extension piece connecting the end of the extruder and head then this needs to be heated to 160oC by heater bands or similar. | |
| Tooling Pressure | Ring die should be the same size or slightly smaller than the final cable diameter. Short land length; no longer than 3mm. The flow path should be as gentle as possible with the adequate separation of the core and ring die. | |
| Tubing | Double taper designs are preferred. Draw down ratios of no greater than 1.5:1 is recommended. | |
| Processing conditions | ||
| Drying | Generally not necessary unless the material is exposed to the atmosphere for a long period of time. In this case, it can be dried in a dehumidifying drier. | |
| Temperature profile | Ranging from 125 to 160oC from the feed to the end of the extruder with 165oC on the head and 165oC on the die. | |
| Melt temperature | Aim for between 160oC and 170oC. | |
| Colour masterbatches | Those from PW Hall are recommended. | |
Troubleshooting guide
|
Problem |
Cause |
Solution |
| Poor surface finish | Temperature low | Increase barrel and head temperatures |
| Use higher shear screw | ||
| Melt fracture |
Increase barrel and head temperatures |
|
| Use lower draw-down ratio | ||
| Reduce extrusion rate | ||
| Extrusion O/D too low | Reduce haul off speed | |
| Change to smaller die (run with slight die swell) | ||
| Improper filling of the die | Use smaller size die | |
|
Porosity |
Compound wet | Vacuum dry, replace material |
| Colour masterbatch wet | Vacuum dry, replace material | |
| Melt temperature too high (decomposition of fillers) | Reduce barrel temperatures | |
| Use lower shear screw | ||
| Check heating and cooling equipment | ||
| Surging extrudate | Insufficient back pressure in extruder | Increase gauze packing |
| Screw speed too high | Reduce screw speed | |
| Porosity in extrudate | See above | |
| Die drool | Low moecular weight material exuding during extrusion | Use highly polished die/point |
| Add 1-2% process aid | ||
| High motor amps | Is motor rating sufficient? | Upgrade motor |
| Incorrect screw design | Use lower shear/compression design | |
| Gauze pack too harsh | Remove some/all gauzes | |
| Head design restrictive | Change head design | |
| Material too stiff | Increase temperature profile | |
| Check heater bands/thermocouples | ||
| Use higher MFI material | ||
| High shrinkage | Draw-down too high | Reduce draw-down |
| Vacuum too high | Reduce vacuum |
© AEI Compounds Limited, Great Stonar House, Sandwich Industrial Estate, Sandwich, Kent, CT13 9LY
Telephone +44 (0) 1304 616171 Facsimile +44 (0) 1304 616170
Email sales@aeicompounds.co.uk Website www.aeicomppounds.co.uk
Whilst this document has been prepared in good faith, AEI Compounds Limited accepts no liability of any kind to any person in respect of its contents or any use made thereof. Neither must it be assumed that any use will not infringe any patent. This document shall not form part of any contract with a customer.