In case of high temperatures, standard self-extinguishing compounds may not be the best solution and other types of materials should be preferred, such as Lati Laramid G/30-V0HF1, based on aromatic polyamide.
Many traditional electrical power transfer applications are made with compounds based on robust and versatile polymers, most notably PA 66. The flame, thermal, chemical and mechanical resistance of self-extinguishing polyamide-based materials is generally very good, even over long periods of use. In some situations, however, the intensity of circulating current and the time of continuous use can put standard PA 66 or PBT solutions in serious difficulty due to the temperature reached by the metal contacts when overheated by the Joule effect.
Scame Parre, a leading Italian manufacturer of electrical components for low-voltage systems, offers contact-holder inserts specifically designed for 125 Ampere heavy duty plugs and sockets used, for example, in industrial plants, construction sites and mines. During continuous operation, temperatures of up to 180-190°C can be reached in these connections, which is more than enough to break down technical polymers such as polyamide and polyester. To avoid having to turn to expensive and complicated high-temperature materials such as ceramics or thermosetting resins, Scame has opted for Lati Laramid G/30-V0HF1, a compound based on aromatic polyamide (PPA) designed to allow continuous use at temperatures well above those reachable by PA66. The resin is reinforced with 30% glass fibre to ensure the rigidity, strength and resilience required to guarantee safe use in challenging conditions, which also include extreme circumstances such as falls and violent impacts.
Obviously, the contact holder must be self-extinguishing and able to withstand contact with metal parts overheated by electric current. This is no problem, given that Laramid has a certified UL94 V0 rating at 0.75 mm and a glow wire flammability index (GWFI) of 960°C for thicknesses of between 1 and 2 mm, both obtained thanks to a halogen and red phosphorus free flame-retardant system. Even though it has a complex formula, which incorporates self-extinguishing additives and glass fibre, Laramid can be processed using traditional equipment. Moreover, aesthetically, the result is excellent, enhanced by the dark brown colour chosen by Scame for its contact holders. Laramid G/30-V0HF1 is also fully certified for use in the railway sector according to the European standard EN45545, boasting maximum rating in R22 and R23 application categories.