ARALDITE® MY 740 / ARADUR® HY 225 / Silica Flour

Because both products contain accelerating additives, avoid storing them for extended periods at elevated temperatures. Incorrect handling of the components can result in undesirable viscosity increases, change in reactivity and substandard Cured-state properties.

• Automatic pressure gelation process (APG) (see our special brochure, Publ. No. 28160/e)
• Conventional gravity casting process under vacuum

General instructions for preparing liquid resin systems

• Long pot life is desirable in the processing of any casting resin system. Mix all of the components together very thoroughly at room temperature or slightly above and under vacuum. Intensive wetting of the filler is extremely important. Proper mixing will result in:

1. better flow properties and reduced tendency to shrinkage
2. lower internal stresses and therefore improved mechanical properties on object
3. improved partial discharge behaviour in high voltage applications.

• For the mixing of medium- to high viscous casting resin systems and for mixing at lower temperatures, we recommend special thin film degassing mixers that December produce additional self-heating of 10-15 K as a result of friction. For low viscous casting resin systems, conventional anchor mixers are usually sufficient.
• In larger plants, two premixers are used to mix the individual components (resin, hardener) with the respective quantities of fillers and additives under vacuum. Metering pumps then feed these premixes to the final mixer or a continuous mixer. The individual premixes can be stored at elevated temperature (about 60℃) for up to about 1 week, de- pending on formulation. Intermittent agitation during storage is advisable to prevent filler sedimentation.
• Mixing time can vary from 0.5 to 3 hours, depending on mixing temperature, quantity, mixing equipment and the particular application. The required vacuum is 0.5 to 8 mbar. The vapour pressure of the individual components should be taken into account. In the case of dielectrically highly stressed parts, we recommend checking the quality consistency and predrying of the filler. Their moisture content should be max. 0.2%.

• Indoor electrical insulators for medium and high voltage, such as switch and apparatus components, bushings, instrument transformers and dry type transformers.
• For mechanically loaded construction parts.

Araldite MY 740 Modified, solvent-free, medium viscous bisphenol A epoxy resin

Aradur HY 225 Liquid, modified, preaccelerated anhydride curing agent

Fig.7.1: Breakdown field strength (A) and holding field strength (B) as a function of storage time (55°C/ 95%rh) Test specimen with embedded sphere electrodes (DIN/ VDE 0303/ part 2 A = raising test; B = 5 min step test)

• Very high resistance to mechanical and electrical stresses
• Very high resistance to thermal shock
• Excellent long-term behaviour in relation to breakdown strength

Determined on standard test specimen at 23°C
Cured for 12h at 80°C + 10h at 130°C

Fig.6.1: Loss factor (tan 8) and dielectric constant (Er) as a function of temperature (measurement frequency: 50 Hz) (IEC 60250/ DIN 53483)

Fig.6.2: Volume resistivity (p) as a function of temperature (measurement voltage: 1000 V) (IEC 60093/ DIN 53482)

Fig.6.3: Breakdown field strength (Ed) as a function of temperature (DIN/ VDE 0303/ part 2, raising test) Test specimen with embedded sphere electrodes

The effective pot-life of the mix is about 3 days at temperatures below 25°C. Conventional batch mixers should be cleaned once a week or at the end of work. For longer interruptions of work, the pipes of the mixing and metering installations have to be cooled and cleaned with the resin component to prevent sedimentation and/or undesired viscosity increase. Interruptions over a week-end (approx. 48h) without cleaning are possible if the pipes are cooled at temperatures below 18°C.For data on viscosity increase and gel time at various temperatures, refer to Figs: 4.1 and 4.2.

Fig.4.1: Viscosity increase at 60 and 80°C (measurements with Rheostress RS100, PP20) (Shear rate D = 3 s-1 )

Fig.4.2: Geltime as a function of temperature (measured with Gelnorm Instrument, ISO 9396)

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. Different gelling and CureCycles in the manufacturing process could lead to a different crosslinking and glass transition tempe- rature respectively.

Determined on standard test specimen at 23°C
Cured for 12h at 80°C + 10h at 130°C

Fig.5.1: Shear modulus (G') and mechanical loss-factor (tan 8) as a function of temperature (measured at 1 Hz./ ISO 6721-7, method C)

Fig.5.2: Coefficient Of Linear Thermal Expansion (a) as a function of temperature (ISO 11359-2, reference temperature: 23C)

First Aid : Contamination of the eyes by resin, hardener or 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.

Store the components at 18-25°C, in tightly sealed and dry original containers. Under these conditions, the shelf life will correspond to the expiry date stated on the label. Product specific advise regarding storage can be found on product label. After this date, the product December be processed only following reanalysis. Partly emptied containers should be closed tightly immediately after use. For information on waste disposal and hazardous products of decomposition in the event of fire, refer to the Material Safety Data Sheets (MSDS) for these particular products