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Sikasil® AS-757 SL

Self-levelling potting compound for electrical components

Sikasil® AS-757 SL is a 2-component, non-corrosive, fast-curing silicone potting compound for encapsulation of electronic parts.  

  • Good flow property
  • Superb dielectric properties
  • Good adhesion to most photovoltaic substrates
  • Very good performance under harsh environment conditions
  • Low volatility
  • UL 94 V0 tested (white color)
 
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PRODUCT BENEFITS

  • Good flow property
  • Superb dielectric properties
  • Good adhesion to most photovoltaic substrates
  • Very good performance under harsh environment conditions
  • Low volatility
  • UL 94 V0 tested (white color)
 

Areas of Application

Sikasil® AS-757 SL can be used for encapsulation and protection of electronic components which may have to withstand harsh environmental conditions. It is designed for junction box potting in the photovoltaic industry. This product is suitable for experienced professional users only. Tests with actual substrates and conditions have to be performed ensuring adhesion and material compatibility.  

Product Details

Typical Product Data
Properties
Sikasil® AS-757 SL (A) Sikasil® AS-757 SL (B)

Chemical base

2-component silicone

Color (CQP001-1)

 

mixed
Black, white Transparent
 Black, white

Cure mechanism

Polycondensation

Cure type

Neutral, alkoxy

Density (uncured)

 

mixed 
1.52 kg/l 0.97 kg/l
 1.41 kg/l

Mixing ratio

A : B by volume

A : B by weight

3.9 : 1

6 : 1

Viscosity (CQP029-6)

 

mixed

9 500 mPa·s

 10 mPa·s

2 000 mPa·s

Consistency

Self levelling, liquid

Application temperature

ambient

5 – 40 °C

Snap time (CQP554-1)

25 minutes A

Shore A hardness (CQP023-1 / ISO 48-4)

55

Tensile strength (CQP036-1 / ISO 527)

1.7 MPa

Elongation at break (CQP036-1 / ISO 527)

40 %

Volume restivity (DIN IEC 60093)

4.8 × 1012 Ω·cm

Electrical strength (DIN IEC 60243-1)

21 kV/mm

Thermal conductivity (DIN 52612)

0.36 W/mK

Service temperature (CQP513-1)

-40 – 150 °C

Shelf life

6 months B

CQP = Corporate Quality Procedure

A) 23 °C / 50 % r. h.B) stored (unopened) in a dry place at ≤ 25 °C
Technical Information

CURE MECHANISM

Sikasil® AS-757 SL starts to cure immediately after mixing the two components.
The speed of the reaction depends mainly on the temperature, i.e. the higher the temperature the faster the curing process. Heating above 50 °C could lead to bubble formation and is therefore not allowed.
The product may also be used in confined spaces but the outgassing by the curing process needs to be considered.
The mixer open time, i. e. the time the material can remain in the mixer without flushing or extrusion of product, is significantly shorter than the snap time indicated above.

Application

Application Information

Surface preparation

Surfaces must be clean, dry and free from grease, oil and dust. Surface treatment depends on the specific nature of the substrates and is crucial for a long lasting bond.

Application

The optimum temperature for substrate and product is between 15 °C and 25 °C.
Before processing Sikasil® AS-757 SL both components have to be mixed homogeneously and air-bubble-free in the correct ratio as indicated with an accuracy of ±10 %. Most commercially available metering and mixing equipment are suitable. For advice on selecting and setting up a suitable pump system, contact the System Engineering Department of Sika Industry.
Consider that the B-component is moisture-sensitive and must therefore only be exposed briefly to air.

 

Removal

Uncured Sikasil® AS-757 SL may be removed from tools and equipment with Sika® Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically.
Re-usable, usually metallic, static mixer can be cleaned with Sika® Mixer Cleaner.
Hands and exposed skin have to be washed immediately using hand wipes such as Sika® Cleaner-350H or a suitable industrial hand cleaner and water.
Do not use solvents on skin.

Overpainting

Sikasil® AS-757 SL cannot be overpainted.

Application limits

To exclude materials influencing Sikasil® AS-757 SL, all materials such as gaskets, setting blocks, sealants, etc., in direct and indirect contact have to be approved by Sika in advance.
Where two or more different reactive sealants are used, allow the first to cure completely before applying the next one.
Sikasil® AS-757 SL may only be used for serial application after a detailed examination and written approval of the corresponding project details by Sika Industry.

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