ARALDITE® B 41 / ARADUR® HT 901 / Mineral Filler

• Void-free epoxy resin castings exhibit outstanding resistance to mechanical, thermal and electrical stress even under long-term loading.
• Low cure shrinkage allows the manufacture of large-volume castings and the crack-free encapsulation of metal parts and conductors.

Indoor electrical insulators for medium and high voltage applications, such as instrument transformers, switchgear components and for structural parts for equipment subject to high mechanical, thermal or chemical stress.

Unmodified, Bisphenol A based epoxy resin. Contains no solvent and is odourless solid at room temperature

Processing Method

• Conventional gravity casting process under vacuum
• The choice of the resin and hardener is determined by the application envisaged and the processing equipment available.
• Pot life and exothermic temperature rise can be controlled by appropriate selection of the resin, hardener and filler combination used.

Fillers

The addition of powdered mineral fillers such as silica flour, microdol and aluminium oxide is recommended when manufacturing castings that will be required to withstand mechanical, electrical or thermal stress.

The incorporation of mineral fillers  :

• Modifies major mechanical and electrical properties
• Reduces shrinkage and exothermic temperature rise during cure
• Imparts a low coefficient of linear expansion
• Improves thermal conductivity
• Reduces unit costs
• The reduction of elongation at break resulting from the use of filler may be a drawback under certain conditions.
• The glow heat resistance and flame-retarding properties of castings can be enhanced by substituting some part of the silica flour filler with Aluminium Oxide Trihydrate. A slight impairment of mechanical and dielectric properties is acceptable.
• Depending on processing conditions and the application for which castings are intended, filler loadings of up to 250 pbw with silica and 350 pbw with alumina may be used.
• The end properties of a casting are dependent to a marked degree on the type, grade, amount and origin of the filler incorporated, on the pretreatment it was given, and on the way it was added to the mix. For instance, silanized silica flour filler has been found to impart appreciably more durable dielectric properties to a casting exposed to tropical weathering. Filler should be predried if it is to be used in high voltage electric castings.
• The impurity content of the filler affects the processing properties of the casting resin mix. It is advisable to test the reactivity and exothermic characteristics with every new batch of filler before continuing production.
• The particle size distribution of a filler influences the flow properties of a casting mix, the gel time and the end properties of castings. Test results deviating from those quoted in this Instruction Sheet are to be expected if casting mixes are formulated using fillers other than those shown.
• Typical silica fillers used are type W 12 from Quarzwerke / hpf or M10 from Sibelco. Coarse fillers have an undesirable tendency to settle out, ultimately promoting built-in stresses in castings.

CAUTION

• Anti-dust safety precautions should always be taken, particularly when filler handling generates fine quartz-containing dust that could cause silicosis.

• The components have to be stored under dry conditions, in tightly sealed original containers.
• Product specific advise regarding storage can be found on product label.
• 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.