High Performance Fillers for thermoset applications
High Performance Fillers play a salient role in the production of Thermosets. The heavy demands made on the many types of duroplasts, such as superior strength, durability and resistance to heat, can only be fulfilled by functional fillers. In addition, the use of such fillers in precast parts makes it possible to create surfaces that are both visually sophisticated and highly durable.
Epoxy resin applications:
For decades now, epoxy resins have been an important material in electronics and electrical engineering, thanks to their excellent adhesive strength, their resistance to heat and chemicals, and their favourable electrical properties. In the electronics industry, epoxy-resin moulding materials are commonly used as coating systems and lamination resins for circuitry, and as auxiliary materials for the production of circuit boards. In electrical engineering, epoxy resins are employed in the manufacture of converters, isolators, and air-cooled transformers. The mechanical, thermal and electrical specification for a given epoxy resin will be determined in large part by the particular type of functional filler to be used. For example, fillers may be based on either silica, fused silica, wollastonite, mica, aluminium trihydrate or white corundum.
SILBOND® silanated, ultra-fine silica flour and MILLISIL® silica flour have a decades-long track record as High Performance Fillers for epoxy-resin systems. Both products not only have exceptional mechanical characteristics, but provide a significant economic benefit as well. Silica-based, High Performance Fillers have the following important features:
• high resistance to weather/chemicals
• high mechanical strength and durability
• good filling power
• excellent processability
• low thermal expansion
Because surface-modified silica flour (SILBOND® W 12 EST) can be effectively incorporated into polymer systems (e.g. by chemical means), this product has long been the standard for weather-resistant, outdoor applications. SILBOND® silica flour is also being increasingly used for “indoor casting-resin parts”, e.g. to achieve optically luminescent, high-end surfaces.
SILBOND® 126 EST represents a further enhancement of the tried and tested, silanated silica flours SILBOND® W 12 EST and SILBOND® W 6 EST. Some of the added benefits of SILBOND® 126 EST:
• The filling level is higher while viscosity remains constant.
- SILBOND® fused silica is ideal for epoxy systems subject to extreme temperature fluctuations.
In electrical engineering, epoxy potting compounds and metallic materials are subjected to strong thermal fluctuations. To prevent damage to a given component, the expansion/contraction of the various materials due to temperature changes must be kept as constant as possible.
Epoxy resin is characterized by a thermal expansion coefficient of 65*10-6K-1.
Metals, on the other hand, have a thermal expansion coefficient between 12-24*10-6K-1.
The use of select high-performance fillers with low thermal-expansion coefficients in epoxy potting compounds makes it possible to minimize divergence in the thermally-induced shape distortions of potting compounds and metals. This is an indispensible prerequisite for applications vulnerable to cracks and tears (large moulded components or complex geometries).
- TREMIN® wollastonite for applications vulnerable to cracks/tears.
Both block-shaped and agicular-shaped TREMIN® wollastonite feature the following:
• good electrical characteristics.
• low thermal expansion.
• excellent reinforcement characteristics.
Flaky micas provide good electrical isolation, superior dielectric strength and excellent thermal resistance.
- White corundum SEPASIL® EK for epoxy
The outstanding characteristic of the aluminium oxide “white corundum” is its resistance to hydrofluoric acid. In addition, the material has good electrical characteristics, excellent thermal conductivity and a high degree of whiteness.
PUR-RRIM applications: TREMIN® 939
TREMIN® 939 needle-shaped wollastonite has decisive advantages for PUR-RRIM (Polyurethane Reinforced Reaction Injection Moulding):
• high tensile strength
• highly scratch resistance
• excellent high-gloss varnishability
SILBOND® cristobalite, MILLISIL® silica flour, SIKRON® ultra-fine silica flour and COLORITQUARZ have a wide range of uses in reactive resins such as PMMA and UP in the context of solid surface/engineered stone applications.
When used for solid surface applications SILBOND®/SIKRON® cristobalite flours provide:
• Clear and luminous tones for blended colours.
• White-toned parts, since the flour’s white colour is retained even in organic composites.
• Scratch-resistant synthetic components impervious to boiling water (for washroom/sanitary uses).
Weisser Quarz (white silica) is an slightly cristobalized, silanated silica sand, consisting of a silica core with a cristobalite coating. Thus, the core provides the stability of silica while the coating adds the more intense whiteness of cristobalite.
In other words, white silica (Weisser Quarz) is just as useful for unground composites as calcinated cristobalite sand, but has a more stable core. As a result, the admixture of silica endows compounds with better mechanical characteristics.
HYDRAFIL® aluminium trihydrate (ATH) is a flame-retardant filler with a superior degree of brightness, and also helps improve mechanical strength and durability. Thanks to ATH’s low Mohs-hardness factor of 3, systems incorporating it as a filler become highly workable and easy to grind. ATH-filled systems are also resistant to dirt and hot water.
COLORITQUARZ (Coloured quartz) is made of pyrite-free, round-grain silica sand, synthetic resin, and pigments with a maximum degree of light fastness. Each grain is evenly coated with a 2-component synthetic-resin system. The product comes in five standard grain size distribution and 700 colours and colour blends. This rich diversity of colours is perfect for creating sophisticated decorative applications. In addition, COLORITQUARZ (coloured quartz) products varnished with an organic coating are more heat-resistant and colourfast than coloured sands with an inorganic coating
Phenol-resin for friction:
By using the functional fillers TREMIN® wollastonite, MICA muscovite, TREFIL® phlogopite, Chinafill kaolin, MILLISIL® silica flour, SIKRON®micronized silica and SILBOND® surface treated silica the following advantages in phenol-resin for friction pads can be achieved:
• reduction of abrasion
• lower degree of noise
• lower degree of vibration
• higher stability of the brakes
• levelling of abrasion (low spread angle of the friction coefficient course)
• mechanical hardness increase of the green bodies in particular