In the “packrafting is tradition” section of this website (as well as the Wikipedia entries - Halkett Boat & Inflatable Boat) it is stated that Lt. Peter Halkett used Macintosh waterproof fabric to build his “cloth boat”. The original Macintosh cloth was made by thinning natural rubber with a solvent then using it to glue two layers of fabric together. This material would have a non-crosslinked polymer material much like the waxed cloth still used to make waterproof clothing. The problem with this material is gluing a seam. The non-crosslinked polymer material would have little structural strength and poor thermal stability - it would liquify if heated. I think that Halkett’s boat construction had to wait until the discovery of vulcanization of rubber by sulfur and heat in 1839 by Charles Goodyear (US patent by Charles Goodyear in 1844 and British patent by Thomas Hancock in 1844) and the development of vulcanized rubber. Macintosh, who had a close association with Hancock, used vulcanized rubber in his fabric after about 1842. Fiber reinforced fabric was covered in Goodyear’s USP# 3633. Vulcanization produces a temperature stable material by forming crosslinked, long chain, tangled molecules. This gives structural strength and flexibility to the polymer and allows the fabric to be glued.
Anyone have any facts or comment?