PLA and ABS is about it for the J head even ABS is at the top of the temp range. You need an all metal hot end the do some of the new materials that need a higher printing temperature
In the last issue of RepRap Magazine RichRap did a hotend review and he says the J-head is the best hotend for extruding Nylon. You can also print with ABS and PLA. But as Dirty Steve said it has to be a real j-head, not a knock off.
