I think I found some Dyneema fishing line for AR$100 a roll at El Brujo, Sarmiento 2443. Green, braided. This scrap of 50-pound (22.7 kg) line he gave me is about 0.35 mm diameter, which works out to 2.3 GPa strength, and it floats, which suggests it is sure enough Dyneema. It’s a Chinese brand and doesn't say “Dyneema”, “Spectra”, or “UHMWPE”. He has rolls of several different diameters for $100, but I don’t know if they’re different lengths or what.
http://articulo.mercadolibre.com.ar/MLA-615447478-multifilamento-dyneema-triple-fish-014-y-018-mm-x-100-m-_JM Triple Fish Bully Braid Dyneema fishing line: 100 meters for AR$305 ≈ US$22. They claim the 0.14 mm diameter line is good to 10.2 kg, which would be 6.5 GPa, almost three times the strength.
https://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene gives 2.4 GPa as its strength.
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA606636 gives a variety of higher strengths in their tests, ranging from 3.63 ± 0.19 GPa up to 4.25 ± 0.21 GPa, with the higher strengths being achieved at higher strain rates up to a kilostrain per second (i.e. loadings more like bullet impacts). For Dyneema SK76, it also shows nice linear Hookean elastic stress-strain curves with a Young’s modulus of about 100 GPa. This is about twice as compliant as a steel, and stronger than most steels.
(Dividing out, 2.4 GPa / 100 GPa is 2.4% elongation at break, which is almost three times what steel gives you. If we suppose the 100 GPa number is accurate for the Bully Braid, that’s 6.5% elongation at break, 65 mm/m, which works out to a spring energy capacity of (65 mm 10.2 kg gravity / 2) = 3.25 J/m; the whole roll holds 325 J for 14.8 J/US$.)
http://www.matbase.com/material-categories/natural-and-synthetic-polymers/polymer-fibers/synthetic-fibers/material-properties-of-dyneema.html#properties suggests that different varieties of UHMWPE have substantially different strengths and very substantially different stiffnesses.
It’s kind of amazing to think that five strands of this fishing line could support me.
https://www.redwoodplastics.com/brochures/uhmw-engineering-data.pdf gives a coefficient of static friction for UHMWPE on steel of .15–.20 and of dynamic friction .12–.20, or .05–.08 if oiled. This suggests that for many purposes, you can run oiled UHMWPE cord around round steel bars without pulleys, avoiding the