Alicia Rul, Nanocyl, presented applications of the company’s multi-walled carbon nanotubes (MWCNTs) NC7000™ including as a co-synergist additive with other PIN flame retardants. The main applications of the product to date (400 tonnes production 2014) are to impart electrical conductivity or mechanical strength to polymers, including application in lithium-ion batteries.
In flame retardancy, the NC7000TM carbon nanotubes increase char production and prevent char cracking, and also appear to trap free radicals (so inhibiting flame) and orientate polymer degradation in fire towards carbonisation (char production) rather than volatisation (flame feeding).
The EU-funded DEROCA project (see pinfa Newsletter 60) has shown that the NC7000TM carbon nanotubes enable a reduced filler load of PIN flame retardants in five different applications (e.g. EN50399 Euroclass B2 in cables compared to reference without NC7000TM achieving Euroclass D).
Nanocyl is fully aware that there is public and regulatory concern about “nano” materials, because their properties can in some cases be very different from standard forms of chemicals, and the company is addressing this with a proactive policy of health testing and transparency. In compliance with generally accepted OECD guidelines, tests were conducted on intake and absorption via the mouth, skin and respiratory passages. The studies found no indications of a harmful effect from potential exposure under realistic industrial conditions. A 90-day inhalation study was conducted on animals in order to evaluate the potential respiratory impacts of NC7000™ multi-walled carbon nanotubes. The results show lung inflammation similar to any inert powder. This confirms health and safety data from workers in the company’s production plant which has now been operating for more than ten years. This positive health profile is coherent with the characteristics of the nanotubes which are short (so not susceptible to physically damage or penetrate cells) and tangled (so not easily absorbed into cells). Also, abrasion studies of polymers containing the nanotubes show that the nanotubes are not released, probably because they are still embedded into the matrix even after strong mechanical stress.