ARALDITE® CY 225 / ARADUR® HY 925 / Silica flour

• High mechanical and electrical properties at elevated temperature
• Very high thermal shock resistance
• Excellent toughness combined with elevated glass transition temperature

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

• Automatic pressure gelation process (APG)
• Conventional gravity casting process under vacuum

• Indoor electrical insulators for medium and high voltage, such as switch and apparatus components.
• Encapsulation of large metal parts.
• Recommended for applications with long term stresses up to service temperature of 85°C.

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 diskharge behavior in high voltage applications.

• For the mixing of medium- to high viscous casting resin systems and for mixing at lower temperatures, we recommend special degassing mixers that may produce additional selfheating of 10-15 K as a result of friction. For low viscous casting resin sys-tems, conventional mixers are usually sufficient.
• In larger plants, the individual components (resin, hardener) are mixed 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°C) 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 vapor 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 <0.2%.

Specific Instructions

The effective pot-life of the mix is about 2 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 installllations 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. Viscosity increase and gel time at various temperatures.

Mold temperature
APG process: 130 - 160°C
Conventional vacuum casting: 70 - 100°C

Demolding times (depending on mold temperature and casting volume)
APG process: 10 - 40 min
Conventional vacuum casting: 5 - 8 h

Cure conditions
APG process (minimal postcure): 4h at 130°C or 3h at 140°C
Conventional vacuum casting: 12h at 130°C or 8h at 140°C

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

Processing Viscosities

Fig. 4.1: Viscosity increase at 40, 60, 80, and 100°C (measured using a Rheomat 115)
(Shear rate: D = 10 s-1)

Fig. 4.2: Initial viscosities as a function of temperature (measured using a Rheomat 115, D = 10 s-1)

Gelation-/Cure Times

Fig. 4.4: Gelation time as a function of temperature (measured using the Gelnorm instrument, ISO 9396)

Fig. 4.5: Glass transition temperature as a function of curing time (at isothermal curing, ISO 11357-2)

Mechanical and Physical Properties

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

Fig. 5.2: Linear coefficient of thermal expansion (α) as a function of temperature (reference temperature: 23°C, ISO 11359-2)

Electrical Properties

Fig. 6.1: Loss factor (tan δ) and dielectric constant (εr) as a function of temperature (measuring frequency: 50 Hz, IEC 60250/DIN 53483)

Fig. 6.2: Specific resistivity (ρ) as a function of temperature (measuring voltage: 1000 V, IEC 60093)

Fig. 6.3: Dielectric strength (Ed) as a function of temperature, with Rogowski electrodes inserted (DIN VDE 0303 Part 2)

A = step voltage test / B = 5-minute step Test

Fig. 6.4: Lifespan curves versus electric field density (E) at 20, 50, 85, 105, and 150°C with inserted spherical electrodes (Ø = 8 mm)

Thermal Endurance

Fig. 7.1: Mass loss
(specimen: 50x50x3 mm)
limit values: 1.2 and 4.0%

Fig. 7.2: IT 150 / 174 (mass loss: 1.2%)
IT 186 / 210 (mass loss: 4.0%)

Fig. 7.3: Decrease in flexural strength
(limit value: 50%) ISO 178

Fig. 7.4: IT 199 / 240 (flexural strength)

Tensile Creep Test acc.

Fig. 7.5: Elongation (ε) in f (t) at 23, 50, and 85°C
Tensile stress: 20 MPa

Fig. 7.6: Creep diagram at 23°C.
Maximum tensile stress as a function of stress duration

Fig. 7.7: Creep diagram at 50°C.
Maximum tensile stress as a function of stress duration

Fig. 7.8: Creep diagram at 85°C.
Maximum tensile stress as a function of stress duration
Thermal Shock Resistance

Fig. 8.1: Cracking resistance/thermal shock test
Specimens that passed the test (%) as a function of temperature
Average fracture temperature: -15°C
Coated metal part. Edge radius: 2 mm

Contamination of the eyes by resin, hardener or casting mix should be treatedimmediately by flushing with clean, running water for 10 to 15 minutes. A doctor should then be consulted.
Material smeared or splashed on the skinshould 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 inhalingvapors should be moved out of doors immediately. In all cases of doubt call for medical assistance.

The components have to be stored in tightly sealed and dry original containers according to the storage conditions on the product label. Under these conditions, the shelf life will correspond to the expiration 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.