If, before we have even started, you are thinking something along the lines of 'first down, now synthetic, what are these guys talking about?', then do not fear, have a look at these two very handy articles published on UKC back in 2012, going into a great deal of depth and explaining the ins and out of technical insulation.
Read more at http://www.ukclimbing.com/gear/news.php?id=7047