ARALDITE® CT 2200 / ARADUR® HY 918 / Alumina

• Resin / filler mixture shows minimal increase in viscosity when stored up to 140°C
• High mechanical end-properties of final part
• Excellent thermal shock resistance

Applications

• Electrical insulation parts for medium and high voltage, such as switch components, bushings and spacer.
• In combination with Alumina filler mainly used for GIS insulating parts.
• Encapsulation of large metal parts

Processing methods

• Conventional gravity casting process under vacuum

ARALDITE CT 2200 CI 
Unmodified, Bisphenol A based epoxy resins

ARADUR HY 918 CI
Low viscosity anhydride hardener

General instructions for preparing prefilled resin systems

• Long pot life is desirable in the processing of any ARALDITE® casting resin system.
• The ARALDITE® resin melted to 120-150°C, together with the dried filler and eventually further additives, will be first premixed under vacuum in the premixer.
• Internsive wetting of the filler is extremely important. Proper mixing will result in:
• Better flow properties and reduced tendency to shrinkage
• Lower internal stresses and therefore improved mechanical properties on object
• Improved partial discharge behaviour in high voltage applications.
• The quantity of premix needed for a casting operation will be transferred to the final mixer and the appropriate quantity of the ARADUR® hardener (at room temperature) will be added.
• After reaching appr. 5 mbar of vacuum, the vacuum pump has to be turned off. Following, the mixer is turned on. After intensive mixing of appr. 15 min the casting resin system is ready.
• The temperature will decrease to appr. 100-120°C and the vacuum did regulate itself to appr. 8 mbar. Now it can be casted directly into the preheated moulds in the autoclave at 100-120°C and under a vacuum of appr. 10-15 mbar.
• The mixing time of the premix (ARALDITE® resin and filler) can vary from 2 to 6 hours, depending on mixing temperature, quantity, mixing equipment and the particular application. The required vacuum is 0.5 to 3 mbar. The vapour pressure of the individual components should be taken into account.
• In the case of electrically highly stressed parts, we recommend checking the quality consistency and predrying of the filler. The moisture content should be ≤0.2%. 

ARALDITE® CT 2200 CI / Alumina premix

• The premix (ARALDITE® CT 2200 CI/Alumina) has, due to his minimal viscosity increase at elevated temperature (120°C), a storage life of approximately 3 days.
• Reactivity dependence on filler type :
• The type of Alumina has naturally a significant influence on pot-life, gel-time and viscosity. Hence, it is recommended to measure this properties with the actual filler intended to use.

General Recommendation (process parameter depend on actual part to be cast )

• To determine whether crosslinking has been carried to completion and the final proper-ties are optimal, it is necessary to carry out relevant measurements on the actual object or to measure the glass transition temperature (Tg).
• Different gelling and cure cycles in the manufacturing process could lead to a different crosslinking and glass transition temperature respectively.

Processing Viscosities & Poltlife
 

* Measured with Rheomat RM 260 / MSDIN 125 / D=10s^-1

Remark : Gel-time is influenced significantly by the type of Aluminia used. 
 

Determined on standard test specimen at 23°C cured for 16h at 140°C 

Fig. 1: Loss factor (tan δ) and Dielectric constant (εr) in f (T)

• (measurement frequency: 50 Hz)
• IEC 250/ DIN 53483

Fig. 2: Volume resistivity (ρ) in f (T)

• (measurement voltage: 1000 V)
• IEC 93/ DIN 53482

• Contamination of the eyes by resin, hardener or casting mix should be treated immediately by flushing with clean, running water for 10 to 15 minutes. A doctor should then be consulted.
• Material smeared or splashed on the skin should be dabbed off, and the contaminated area then washed and treated with a cleansing cream (see above). A doctor should be consulted in the event of severe irritation or burns. Contaminated clothing should be changed immediately.
• Anyone taken ill after inhaling vapours should be moved out of doors immediately. In all cases of doubt call for medical assistance.

• The components have to be stored under dry conditions at 18-40°C, in tightly sealed original containers.
• Under these conditions, the shelf life will correspond to the expiry date stated on the label.
• After this date, the product may be processed only following reanalysis.
• Partly emptied containers should be closed tightly immediately after use.