ISO-PUR® K781-FR
Flame retardant in accordance with UL 94 V-0 (3 mm)
ISO-PUR® K781-FR is a mineral-filled, cold-curing, 2-component polyurethane casting resin based on polyether and ester polyols and polymeric aromatic diisocyanates. After curing, the casting compound forms hard-elastic, hydrolysis-stable molded bodies. The material has passed flame retardancy tests according to UL94 V-0 (3 mm) and is therefore particularly suitable for encapsulating electrical components tested according to UL standards. Cured materials of ISO-PUR® K781-FR do not contain any plasticisers and do not tend to become brittle. ISO-PUR® K781-FR is particularly suitable for the use in components subject for high mechanical and thermal stress. The system is characterised by excellent heat dissipation and minimal shrinkage during curing. ISO-PUR® K781-FR shows good corrosion protection properties and high adhesion to metal, ceramics, and many plastics. The product is compliant according to EU Directives 2011/65/EU (“RoHS”) and 2015/863/EU (“RoHS III”).
Technical data
Downloads
Resin
Colour
Viscosity (25°C; rot.; 1 s-1)
Viscosity (25°C; rot.; 10 s-1)
Density (23°C)
Beige (other colours on request)
Approx. 18300 mPas
Approx. 10100 mPas
Approx. 1,69 g/cm³
Hardener
Type
Colour
Viscosity (25°C; rot.; 1 s-1)
Viscosity (25°C; rot.; 10 s-1)
Density (23°C)
ISO-PUR® Hardener
Brown
Approx. 130 mPas
Approx. 120 mPas
Approx. 1,23 g/cm³
ISO-PUR® Hardener LV
Brown
Approx. 50 mPas
Approx. 30 mPas
Approx. 1,23 g/cm³
Mixture
Mixing ratio resin : hardener
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Colour
Beige (other colours on request)
Density (23oC)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 1,58 g/cm³
Approx. 1,58 g/cm³
Pot life (23°C) /
Gel time (23°C)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 40 min / approx. 80 min
Approx. 70 min / approx. 160 min
Mixed viscosity (25°C; rot.; 1 s-1)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 2500 mPas
Approx. 1000 mPas
Mixed viscosity (25°C; rot.; 10 s-1)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 2100 mPas
Approx. 1000 mPas
Cured product
Mixing ratio resin: hardener
Under standard curing condition
4 : 1 parts by weight
(14 days 23°C / 50% relative humidity) unless otherwise stated
Hardness Shore D
(23°C; 14d RT 50% rel. h.) /
Hardness Shore D
(23°C; oven curing: 4hRT + 24h80°C)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 86 / approx. 86
Approx. 86 / approx. 86
Long-term temperature resistance /
Short-term temperature resistance
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 155°C / approx. 200°C
Approx. 155°C / approx. 200°C
Glass transition temperature (midset)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 45°C
Approx. 45°C
Tensile strength (5A specimen)
(2 mm thickness; speed: 10 mm/min; 23°C)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 40 N/mm2
Approx. 40 N/mm2
Elongation at break (5A specimen)
(2 mm thickness; speed: 10 mm/min; 23°C)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 3%
Approx. 3%
Tear resistance
(W-specimen; incision; speed: 10 mm/min; 23°C)
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 100 N/mm
Approx. 100 N/mm
Dielectric strength
4 : 1 parts by weight
4 : 1 parts by weight (LV)
> 20 kV/mm
> 20 kV/mm
Thermal conductivity
4 : 1 parts by weight
4 : 1 parts by weight (LV)
Approx. 0,90 W/K×m
Approx. 0,90 W/K×m
Storage and transport
Store in a dry and airtight, closed container at 10 – 35°C. Can be stored for at least 12 months in original sealed containers under the above conditions. Short-term deviations during transport and storage are acceptable.
Cleaning
To ensure good adhesion of the cast resin the customer should individually test the suitability of the involved surfaces. Possible pre-treatments like cleaning, activation processes (plasma process) etc. should also be taken into account. The contact surfaces should be free of dirt such as dust, grease or water. For cleaning we recommend ISO-RC® Degreaser for wipe degreasing or ISO-RC® Flux-Off + ISO-RC® Spraywash for spray degreasing (available in 400 ml spray cans).
Processing
Stir up the resin container thoroughly before use to remove any possible sedimentation. Weigh the resin and hardener in the desired mixing ratio and mix for 1 – 3 minutes (depending on mixed quantity and processing time). Apply suitable mixing speed in order to ensure complete homogeneous mixing without introducing too many air bubbles into the reaction mass. The ideal processing temperature is 20 – 25°C and a relative humidity of less than 40%. In general, curing is delayed at lower temperatures and accelerated at higher temperatures. When using a double chamber bag, empty the corners thoroughly and knead for 3 minutes. When using a double chamber bag, empty the corners thoroughly and knead for 3 minutes. Before casting, a homogeneous mass, free of streaks, must be obtained. Pour immediately afterwards and do not scrape the mixing vessel. Air bubbles that have been stirred in, can be removed before the end of the potlife by evacuating the material or carefully fanning the surface with a hot air gun. Machine casting is also possible.
The EC safety data sheet provides information on safety-relevant product properties.
Hardener component (containing diisocyanate): As of August 24, 2023, appropriate training must be provided before industrial or commercial use.