Coolmax or Dri-FIT?

The predominant fabrics used in the tit slings I discussed in the prev. post are:

• Polyester/Lurex®/Coolmax®/Dri-FIT
• Spandex/elastane/lycra
• Nylon/polyamide
• Cotton

Each fabric has its advantages and disadvantages

• Tenacity (Tensile Strength) dry or wet
• Abrasion Resistance
• Absorbency/ability to wick moisture
• Stability under heat and UV
• Tendency to Mildew

Humphries, Mary.  Fabric Reference, 4^th Ed.
Prentice Hall, 2009, p. 16.

This image relates groups of textiles; both manufactured fibers (shoots) and natural fibers (roots).  It took me awhile to untangle the branches, seeing as how there are many names for polyester and nylon.  As far as I can tell, spandex is similar to polyester but more rubber-like, being able to stretch to 500 times its original length.  I thought Lurex was pretty cool, it seems to be a metal-coated polyester that was only in one type of my bras, giving it a shimmery quality (Carmel).

According to Humphries, the advantages to polyester are that it has good strength and resistance to abrasion, but it collects oily stains, has low perspiration absorbancy and tends to pill.  The advantages of spandex is that it is elastic and 10 times stronger than rubber, it can be used uncovered, it is more resistant to oil and dry heat than rubber, and it takes dye.  The advantage to nylon is that it has the greatest strength and resistance to abrasion, but it has low UV light resistance and tends to pill.  The advantages to cotton are that it is absorbent and strong when wet, but it swells in water and has a tendency to mildew.

Simile, Craig B. (2004) Critical Evaluation of Wicking in Performance Fabrics, M.Sc. Georgia Institute of Technology: USA. p. 15

With both manufactured and natural fibers, there are shapes of the individual fibers that make up the spun bundles of fibers (yarn).  Mary Humphries does a good job of presenting what many natural fibers would look like under a microscope.  Craig Simile, in his Master's thesis, presents a microscopic view of an individual fiber of Coolmax.®  By testing a variety of materials, he concluded that fabric with yarns containing larger effective capillary radii (pores) had higher permeability at high levels of saturation (very sweaty people).  Once saturation dropped below a certain level (less sweaty people), the yarns with smaller effective capillary radii were able to sustain higher permeability.  I would conclude then that Coolmax® or Dri-FIT are better for less sweaty individuals while cotton is better for more sweaty individuals, due to its large pores.  A major finding of this work is that the ability of a fabric to wick moisture depends on the amount of saturation, so there may not be one ideal fabric for every athlete.

Kan, et al. Materials, 2013, 6, 4985-4999.

One interesting side effect of porosity of a fabric that was considered by Kan, et al. is that UV protection offered by Cotton alone (SPF 10-20) is inferior to Cotton/Coolmax-Blended knitted fabric (SPF 20-40).  The figure presented here shows that the highest SPF was recorded by Coolmax in combination with conventional ring spun combed supima cotton, followed closely by Coolmax alone.  When a garment is worn, such as my old worn out Performance bicycle shorts (80% NYLON & 20% LYCRA), light is allowed to enter just as sweat and hot air are allowed to escape.  When I go for a bike ride now, I've got to wear a little skirt over my cycling shorts, otherwise I end up with a train of men following me.  I've not been chatted up by so many guys (young and old) as last weekend when we were walking around Pasadena in our Spandex.  It appears that Coolmax is better at keeping lightly-to-moderately sweaty people dry as well as protecting them from the sun.  Sorry super-sweaters, you are at greater risk to suffer a sunburn if you are in the heat and dressed in cotton, but at least you will be able to keep cool!

Shillingford, C.; MacCallum, N.; Wong, T.-S.; Kim, P.; Aizenberg, J. Fabrics coated with lubricated nanostructures display robust omniphobicity. Nanotechnology 25 (2014) 014019, p. 6.

If you're wondering what I'm talking about with reference to porosity, check out these scanning electron microscope images of Nike Dri-FIT (polyester) in panel B with thread width 200 microns in a square weave pattern when compared with Muslin cotton in panel D with thread width 350 microns.  The Nike Dri-FIT showed poor breathability.  The researchers measured how much water transpired through the fabrics compared to a dish completely covered with Parafilm and a dish covered with Parafilm with a large hole poked into it.  These fabrics have many tiny holes. Dri-FIT did not allow a significant amount of water to be transpired through it, while cotton allowed most of the water to evaporate!

Hopefully in a future post, I can take this discussion from the microscale to the nanoscale and talk more about the polymers which make up these fibrous materials.  I've read a statistic that sports bras are only good for 72 washes, possibly because nylon and polyester are sensitive to strong alkali (most laundry detergents).  This is why I always treat my delicates with a neutral pH detergent (Woolite) and wash them on a gentile cycle.  Also, I dry them on a clothesline rather than in the dryer.

Works Cited:

• Humphries, Mary. Fabric Reference, 4th Ed. Prentice Hall, 2009, p. 16
• Simile, Craig B. (2004) Critical Evaluation of Wicking in Performance Fabrics, M.Sc. Georgia Institute of Technology: USA. p. 15
• Kan, C.-w.; Yam, L.-y.; Ng, S.-p. The Effect of Stretching on Ultraviolet Protection of Cotton and Cotton/Coolmax-Blended Weft Knitted Fabric in a Dry State. Materials 2013, 6, 4985-4999.
• Shillingford, C.; MacCallum, N.; Wong, T.-S.; Kim, P.; Aizenberg, J. Fabrics coated with lubricated nanostructures display robust omniphobicity. Nanotechnology 25 (2014) 014019, p. 6.
• More about Polyester http://en.wikipedia.org/wiki/Polyester or http://en.wikipedia.org/wiki/Olefin_fiber
• More about Spandex http://www.madehow.com/Volume-4/Spandex.html
• More about Nylon http://www.chemguide.co.uk/organicprops/amides/polyamides.html or http://en.wikipedia.org/wiki/Nylon
• 7 Underwear Facts that might Surprise You http://www.shape.com/lifestyle/beauty-style/7-underwear-facts-might-surprise-you/
• 5 Reasons NOT to wear a Thong to the Gym http://yearofthedetox.com/2012/02/18/5-reasons-not-to-wear-a-thong-to-the-gym/