>>1172439>>1172964Densities are:
Wool 1.32 g/cm^3
Nylon 1.15 g/cm^3
Polyester 1.38 g/cm^3
A 80/20 by weight wool/nylon blend would be 77/23 by volume, so anon is correct here. A wool/polyester blend would actually have higher wool content by volume.
However, poly fibres can be considerably thinner than wool fibres, thus accounting for a higher share of the fibre length (assuming a simple 1/2 relationship of thickness, we would arrive at a mere 46% wool fibre length for the 80/20 wool/nylon blend).
Does this matter? Good question. The capacity to absorb water into the fibres (without losing insulation) is probably related to weight. The capacity to shed water *might* be related to the surface (as in, wether there's wool or nylon getting into contact with water drops) and depending on the weave and treatment, there might be more nylon than wool there.
In my experience, nylon blends are usually for strength, so I would assume thick nylon fibres and little effect. (Also, the surface can be all wool with the right fabric construction.) Polyester blends are often used in cheap wool garments, where I would assume it is actually meant to increase the felt thickness of the fabric and its warmth. Thus they would probably use finer fibres, arriving at a fabric whose volume and thus warmth is more significantly created by the polyester, but is generally lighter than an all wool fabric of similar warmth. This fabric would absorb water worse due to having less wool in total and shed it less due to being composed of wool by only about 50% on the surface (assuming a polyester fibre exactly half the thickness of a wool fibre ).
