You rarely ever see or hear about polyester and silk blend fabrics in the outdoors world. You have pure, thin silk garments which are somewhat used/known about (REI, Terramar, etc), but polyester-silk blends are virtually unheard of, with the exception of certain versions Dri Release that uses like 11% silk.
I think this is an over-site and we may be missing out some. Silk has a lot of good properties that make it a good fabric for cool to cold weather–in many ways it's better than wool for thinner and lighter garments. It's significantly stronger than wool and absorbs less moisture.
However, there are some issues like with any fiber, natural or synthetic–there is no, perfect in all conditions fiber. Like wool, i think silk would be much better when blended with a synthetic. First, some attributes and pros and cons of silk by itself.
Naturally good insulator: Good quality silk fibers tend to be very fine, averaging from around 5 to 14 microns. With the exception of the finest and most expensive Merino or rare/specialty fibers like Qiviut, this blows most wools out of the water. Hence, it can potentially trap a certain amount of air per thickness. It's a trilobal shape, which in a study i read when it compared round fibers to trilobal shapped ones, the latter trapped/still more air. Lastly, like other animal proteins, it's thermally resistant, so like wools and certain synthetics (especially polypropylene and polyester), it will be warmer while wet than cellulose or certain synthetic based fabrics.
It's quite a strong, and fairly durable fiber for being natural. MUCH stronger in a one on one fiber comparison to a say a sheep's wool fiber.
It absorbs significantly less moisture than does Sheep's wool.
Like all natural (or semi-natural–tencel, modal, rayon, etc) and absorbent type textiles, it has at least decent odor prevention/reduction, and what odor it does build up can be easily washed out.
Comfortable: That same low micron count, and without scales or barbs of Sheep's or other wools, makes it a very soft feeling fabric. The absorbency makes it a breathable and comfortable fabric provided not too much sweat is involved. It has a little innate stretch, but not a lot like sheeps wool.
Cons: It is not that UV resistant (which in a baselayer is not that important), it's expensive, it can be easily overwhelmed with sweat, and it does lose some strength when wet. It's not as durable as most synthetics are, particularly in comparison to polyester and especially nylon. But that's a strike against all natural fibers really. Not near as good odor prevention as the various wools, but still much better than untreated nylon and especially polyester and polypropylene.
I've tried all silk type baselayers for active conditions. It's not the best material in the world for that, because it can be overly clingly and take a little while to feel drier.
Solution: Use fabrics that contain at least 30% silk blended with polyester. This reduces odor some, greatly improves wicking without having to alter the polyester fibers, potentially increases insulation a bit, improves comfort via adding softness and breathability though polyester microfiber can be softer than silk even, decreases overall cost of said garment, increases drying time, increases UV resistance. Increases "eco" friendliness a bit since silk can be completely broken down without toxic waste byproducts, but also signficantly increases longevity/durability of said garment which has it's own eco pluses.
Silk has similar moisture regain as tencel. Lenzing did an interesting study on comfort level of blends of tencel with polyester during active, sweaty use. Lenzing, like Optimer (maker of Dri Release), found that most people preferred the feel of natural and semi-natural fiber garments to synthetics when dry. But as sweat increased addition of higher proportion of hydrophobic fibers blended in, helped increase comfort level. Optimer seems to have done the most testing with cotton and polyester blends. As you know, cotton is notorious for holding onto moisture. This is both because of it's absorbent, cellulose based nature and i also think because of the structure of the fiber itself.
Anyways, they found an ideal range of about 15% cotton to 85% synthetic (polyester mostly) to find that nice trifecta balance between increasing wicking, comfort of feel, and drying times.
Lenzing's studies were a bit different in specific conclusions, they found a 30% tencel to 70% polyester ratio blend performed better than all polyester, all tencel and other ratios of blends as far as comfort and drying time with sweat being involved (it seems this may be because tencel while slightly more initially absorbent than cotton, it may actually release moisture more efficiently and quickly than cotton. This is similar to comparing linen to cotton ime).
Since silk and tencel have a similar moisture regain, i hypothesize that the ideal ratio blend of polyester and silk will be similar as Lenzing found with tencel and polyester. Well, lucky me, i found such a fabric. I'm going to experiment with using it both as a baselayer, and also as lighter weight mid layer over polypropylene fishnet baselayer. If you are interested in hearing about it, let me know, otherwise i probably won't post updates.
Another blend with good potential for cool to cold weather garments, would be a blend of polyester, alpaca, and silk. Something like 60% polyester, 23% alpaca, and 17% silk should have a nice balance of odor reduction, durability, drying time, comfort, wicking/breathability, etc. Would be much more durable than Merino and Merino/synthetic blend baselayers, as well as quicker drying and slightly more insulating (all other factors being the same). Unfortunately, cannot find any fabrics or garments with a similar blend ratio.
