Sixteen HFFR materials have been tested for short and long term properties.

Significant improvements compared to previously tested materials have been observed.

Some materials have been found with extremely good properties in one respect and very poor in another and some with acceptable but not extremely good properties in all respects.

The tests also show that the best materials have properties which are comparable with those of PVC with regard to dry and wet ageing, oil resistance, and UV resistance. This means that if they are tested and selected properly the HFFR materials can be used in environments that were not considered previously such as in buried cables, with oil contact at moderate temperatures and exposed to sunlight (if stabilized properly).

Tests of two cross linked compounds showed no significant advantage.

The processing properties of some of the tested materials were very good but unfortunately these easy processing types had serious drawbacks in other respects like burning properties which are of great importance.

For the high viscosity types that were more difficult to process significant process improvements (line speed) have been achieved during the production of optical cables by adjusting screw and die geometry. The improvements have been verified by the production of test cables with excellent properties.

The adjustments were based on computer simulation of the extrusion process with HFFR materials thoroughly characterized by rheological measurements. The agreement between values from the computer simulation and values measured on the cable production extruder was acceptable.

The positive effect of mixing elements in the extruder screw has been demonstrated.

The results of the project is or will be implemented in the production of optical cables.

Concerning the prossibilities of increasing the line speed during the production of installation- and power cables further development work have to be carried out.
Improvement of the design of the extruder screws and head toolings have to be accomplished or lower production speed than for cables based upon PVC compound have to be accepted. Which will require capital intensive investments in new production lines if the same production output shall be achieved.