No, N is for neoprene/polychloroprene, used as the outer sheath of H05RN-F and H07RN-F for its excellent water resistance (for service outdoors and in otherwise wet areas). And again, there's a higher grade "N4" for 90°C operation (the North American "HPN" [Heater Parallel Neoprene] cords, designed for immersion heating elements, are also insulated with something similar; its dimensions are equivalent to SPT-2 in 18/16AWG and SPT-3 in 14/12AWG, although with #34 strands in all sizes where SPT-3 has coarser #30 strands in the larger sizes to reduce the price - typical penny-pinching if you ask me). I've checked and I haven't seen any cords still made with natural rubber - which is pretty much entirely obsolete technology anyway (certainly, it's anything but durable compared to the modern materials).
My only major complaint here is that, in my view, plated conductors should be made mandatory with the common elastomers, even where not required by the manufacturing process itself (some synthetic rubber formulations still require plated conductors, while others including EPR can be manufactured with bare copper conductors); while bare copper cores have marginally lower initial resistance, as noted earlier the most common synthetic elastomers provide only minimal protection from oxidation, so by the end the ultimate resistance ends up far higher than the resistance of tinned (or nickeled, silvered etc.) conductors will ever be. The plastics, fluoropolymers (PTFE, FEP, etc.) and silicone rubber all provide far better protection, so bare copper cores hold up fine under them (except at service temperatures above 150°C).
If you doubt me, you always have the option of checking on the manufacturers' websites. To the best of my knowledge, low-quality electrolytic capacitors are the only thing in electronics that still use natural rubber for their seals (as it's cheaper than synthetic rubber and will last through the warranty period). The high-quality ones (mostly from the Japanese brands at present) use synthetic rubber, although Nippon Chemi-Con and Nichicon still advise a maximum 15-year expected service life but that's probably for legal butt-covering as much as anything else to be realistic.
EDIT: I am replying to you, Ranger, only I accidentally used the "reply" button provided for the topic.
Last edited by LongRunner; 07/08/15 11:42 PM.
