LT XLPE Compound PP 408/401

A silane grafted crosslinkable polyethylene compound, curable by exposure to moisture, for insulation of power cables and possessing excellent extrudability at high output rate.

PP 408 is based on high molecular weight polymer and has melt flow index in the range of 1.0 to 1.4. It has been especially developed for low Voltage Cable Insulation and for Sheathing Purpose. Silane grafted cross linkable polyethylene for low voltage power cable insulation.

Technical Characteristics

Properties- Physical & Mechanical Typical value Unit Test Method
Density 0.925 gm/cm3 ASTM – D- 1505
MFI at 190° C / 2.16 kg. 0.5 G / 10 PPIL

Unaged mechanical properties :

Tensile Strength at Break 18 MPa IEC60811
Elongation at Break 550 % IEC60811

Mechanical Properties after ageing in Air oven, 168 hr. at 135 C:

Variation on tensile strength 10 % IEC60811
Variation on elongation at break 15 % IEC60811

Hot set test, 15 min. at 200° C, 0.2 N / mm2:

Elongation under load 100 % IEC60811
Permanent Elongation after Cooling 5 % IEC60811

Electrical Properties :

Power factor at 50 Hz at 23° C 0.0004 Nil 0.0004
Dielectric constant 2.3 Nil IEC250
Volume Resistivity at 20° C 2.4*1016 IEC502
Dielectric Strength 25 Kv / mm IEC243

Special Characteristics

It is a two component system comprising a silylated Ethlene Polymer known as the graft copolymer PP 408 and a master batch PP 401 Containing a cross linking catalyst. The two materials are normally used in the ratio of 95 parts graft to 5 parts catalyst master batch.

Stored separately, these materials are fairly stable but when mixed and exposed to moisture, cross linking takes place

Recommended Extrusion Conditions

Extruder :

Thermoplastic extruders will process PPIL Sioplas – type compound particularly if the screw is suitable for polyethylene extrusion. An extruder having L/D ratio of at least 20 and compression of 3:0:1 is recommended.

Extrusion Temperature Conditions:
As a guide the following temperature profile is recommended:
Zone 1 Zone 2 Zone 3 Zone 4 Head Die
160° C 170 ° C 180° C 190° C 200° C 210° C
This profile may vary depending on extruder type, design and output
Screw water temperature: 60° C – 70° C
Screens: 30,80,30 (mesh apertures per linear inch)

Head And Tool Design :

The head and tools should be so designed to allow streamline flow without the possibility ofstagnation material

To obtain optimum physical properties in the case of tubing tools, it is generally recommended that a draw down ratio not greater than 3:1 should be used both for sector and round shaped conductor. PPIL engineers would be glad to provide comprehensive details of recommended tool design for both round and sector shaped conductor.

Cross-Linking or Cure :

This Curing can be done in the following ways :
• By immersion in hot water at 90-95°C
• By exposure to low pressure steam (about 0.15 bar)
Following factors are important for cure
• The ratio of conductor to insulation thickness
• Barrel diameter of the cable on which the core is cured
Master Batch:

It is recommended that the catalyst master batch be thoroughly dried before usage at 60°C for 18 hrs. at a depth not greater than 5 cm. (Base of try should have Perforation)

Storage :
Store under cold and dry conditions for best results
Packaging :
Moisture resistant aluminum laminated bags of 25 kg.

This information is to the best of our knowledge. The values of different parameters and operating conditions listed above are guidance only and should not be used for drawing specifications. The results & operating conditions may vary depending on methods of test and manufacturing / testing equipments