XLPE Compound for 33KV Cables PP 409-401 (S)

A Silane Grafted Crosslinkable Polythylene Compound, curable by exposure to moisture, for insulation of power Cables and possessing excellent extrudability at high output Rate. PP 409 has been specially developed for cables up to 33KV. The special formulation and compounding techniques used PP 409 has general Melt Flow Index range of 0.7-0.1, which provides firm stability during extrusion, especially for the thick insulations required for high voltage. Silane Grafted Crosslinkable Polythyles For Medium Voltage Power Cable Insulation.



Special Characteristics:

The compound utilizes the system for crosslinkable of polyethylene developed by Dow Coring and known as Sipolas. It is a two competent system comprising a Silylated Ethylene polymer . known as the graft PP411 and a masterbatch PP401 (CL) containing a crosslinking catalyst. The two material normally used in the ratio of 95 parts graft to 5 parts catalyst masterbatch.

Stored separately, these material are fairly stable but when mixed and exposed to moisture, crosslinking takes place.

This system allows the compound to be extruded as a normal thermoplastic which will then attain a high level of crosslinking in the processed form. The finished product has all the properties associated with polyethylene crosslinked by other methods.

Technical Characteristics

Properties- Physical & Mechanical Typical value Unit Test Method
Density 0..75 gm/cm3 ASTM – D- 1505
MFI at 190° C / 2.16 kg. 0.55 Gm/10min. PPIL

Unaged mechanical properties :

Tensile Strength at Break 14.5 MPa IEC60811
Elongation at Break 400 % IEC60811

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

Variation on tensile strength 15 % IEC60811
Variation on elongation at break 10 % 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 IEC60250
Dielectric constant 2.2 --------- IEC60250
Volume Resistivity at 20° C 1.4*1017 Ohm.cm IEC60502
Dielectric Strength 24.7 Kv / mm IEC60243

Special Characteristics :

It is a two component system comprising a Silylated Ethylene polymer known as the graft copolymer PP 409 and a masterbatch PP 401 (S) containing a crosslinking catalyst. The two materials normally used in the ration of 95 parts graft to 5 parts catalyst masterbatch.

Stored separately, theses materials are fairly stable but when mixed and exposed to moisture, crosslin king takes place.

Contamination : (upto 33KV)

Contamination is measured by the use of the Dyanascope's micrometer (x200)
Level of Contamination
1. a) no particle>0.3mm
b) max. particle 5 per 500 gm between 0.20 to 0.29 mm

Recommended Extrusion Conditions :

As a guide the Thermoplastic extruders will process PPIL Sipolas type compound particularly if the screw is suitable for polyethylens extrusion. An extruder having L/D ratio of at least 20 and compr ession of 2.5:1 is recommended.

Zones I II III IV Head Die
Temperature 150°C 160°C 170°C 180°C 190°C 190°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 of stagnation material

Curing can be done in the following ways :

Conductor and Core Screens :

Compound PP 411/401 (CL) may be used in conjunction with deformation resistant thermoplastic Semiconducting material PPIL grade- P-10040-CB for conductor and insulation shield.

Cross-Linking or Cure :

• By immersion in hot water at 80-85°C
• By exposure to low pressure steam (about 0.15 bar)
Following Factors are important for Cure :
• The ratio of conductor or insulation thickness
• Barrel diameter of the cable on the core is cured.

For thickness greater than 4 mm(approx) a maximum temperature of 85°C (which is below the phase change temperature of PP 411) is recommended, otherwise a set in the shape of the core will occur, preventing the core from lying flat after removal from the drum. Morover higher temperature may soften the outer semicon layer and cause damage.

The period required to obtain full cure will depend upon insulation thickness but typical periods in steam atmosphere are as under :

Insulation thickness Temperature Time
3-6 mm 85°C Above 24 hr.
8 mm 80°C 190 hr.
15 mm 80°C 280 hr.
This Curing can be done in the following ways :
By immersion in hot water at 80-85°C
• By exposure to low pressure steam (about 0.15 bar)
Following Factors are important for Cure :
• The ratio of conductor or insulation thickness
• Barrel diameter of the cable on the core is cured.

For thickness greater than 4 mm(approx) a maximum temperature of 85°C (which is below the phase change temperature of PP 411) is recommended, otherwise a set in the shape of the core wil l occur, preventing the core from lying flat after removal from the drum. Morover higher temperature may soften the outer semicon layer and cause damage.

The period required to obtain full cure will depend upon insulation thickness but typical periods in steam atmosphere are as under :

Insulation thickness Temperature Time
3-6 mm 85°C 3-6 mm

A significant decrease in cure time is possible through immersion in pressurized water (1.3bar) at a temperature of 85°C.

• 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 4hrs. at a depth not greater than 5 cm.

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

This information is to the beat 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.