MicroModal vs Cotton vs Bamboo vs Polyester: Which Underwear Fabric Handles Gulf Heat?
By the Unluckies team · Last reviewed 25 Sep 2026 · Sources listed at the end
We make our boxer briefs from MicroModal, so we have a point of view. That is exactly why this comparison sticks to published research and says where other fabrics do better. Part of our Gulf Heat Underwear Guide.
The short answer
- All-day wear in Gulf heat: modal / MicroModal. It absorbs more moisture than cotton, moves it quickly, and stays soft.
- Hard training and very sweaty sessions: light polyester blends. They hold very little water and dry fastest.
- Cotton: comfortable and familiar, but it holds moisture and dries slowly compared with light synthetics.
- "Bamboo": usually viscose (rayon) made from bamboo pulp. Expect it to behave like other viscose, not like a special fibre.
What actually matters in the heat
- Moisture regain. How much water vapour a fibre takes up from the air under standard conditions. Higher means it absorbs sweat vapour rather than leaving it on the skin.
- Wicking and spreading. How fast liquid sweat is pulled in and spread out so it can evaporate.
- Drying time. How long the fabric stays wet.
- Feel and fineness. Finer fibres make a smoother, softer fabric.
- Fabric build. Weight, thickness and knit often matter as much as the fibre.
Side-by-side
| Modal / MicroModal | Cotton | "Bamboo" (viscose) | Polyester | |
|---|---|---|---|---|
| Fibre type | Regenerated cellulose (from wood pulp) | Natural cellulose | Regenerated cellulose (bamboo pulp) | Synthetic |
| Moisture regain | ~11.8% (modal) [1] | ~7–8% [1]; 8.5% is also used [2] | ~11–14% (viscose) [1] | ~0.4% [2] |
| Absorbency vs cotton | about 50% more water-absorbent per unit volume [2] | baseline | similar class to modal (both regenerated cellulose) [1] | far lower [2] |
| Drying | depends on build; holds more water than polyester | cotton-rich underwear knit ~25 min in one lab test [3] | depends on build | thin polyester/elastane knit ~3 min in the same test [3] |
| Feel | very soft; "micro" versions use the finest modal fibres [4] | soft, gets heavier when wet | soft | smooth; many find it less soft for all-day wear |
| Best for | everyday wear, long days, under a thobe or kandura | cooler days, sleep, budget | everyday wear (like other viscose) | gym, running, sport |
Numbers are fibre-level or single-study results. Real garments vary with weight, knit and finish.
Fibre by fibre
Modal and MicroModal
Modal is a regenerated cellulose fibre made from wood pulp. A review of regenerated cellulose fibres lists modal's moisture regain at about 11.8%, versus about 7–8% for cotton [1]. A textile-engineering study describes modal as about 50% more water-absorbent per unit volume than cotton [2]. In a moisture-management study of knitted fabrics, single-jersey modal wicked and spread moisture in about half the time of the other cellulosic fibres tested [5]. "MicroModal" refers to modal made as very fine fibres. Fibre producer Lenzing describes its micro modal as the finest in its range, giving extra softness [4].
Trade-off: because modal absorbs water, a modal fabric holds more moisture than a thin polyester, so it will not dry as fast as a sports synthetic.
Cotton
Cotton is breathable and familiar. Its moisture regain is lower than modal's (about 7–8%) [1], but a cotton knit still soaks up liquid sweat and can stay damp. In a lab study of 18 knitted fabrics, cotton-rich underwear fabrics took roughly 25 minutes to dry, compared with about 3 minutes for a thin polyester/elastane fabric, under the same conditions [3].
Trade-off: great on cooler days and for sleep. On a long, hot, humid day it can feel heavy and damp.
"Bamboo"
Most fabric sold as bamboo is not bamboo fibre. It is viscose (rayon) made using bamboo as the cellulose source. The US Federal Trade Commission says such products should be labelled "rayon (or viscose) made from bamboo", and that claims about natural bamboo properties surviving into the fabric need evidence [6][7]. Viscose sits in the same regenerated-cellulose family as modal, with moisture regain around 11–14% [1].
Trade-off: can feel lovely, but judge it as viscose, not as a special fibre.
Polyester
Polyester is hydrophobic, with a moisture regain of about 0.4% [2]. It barely absorbs water. Sweat moves along its surface and evaporates, so thin polyester knits dry very fast [3]. That makes it the favourite for intense sport.
Trade-off: less absorbent means sweat can sit on the skin until it moves along the fabric, and many people find it less soft for all-day wear.
Fabric build matters as much as fibre
In the same 18-fabric study, heavier and denser fabrics generally moved moisture less well, and the thinnest fabric dried fastest [3]. A thin modal knit and a thick modal knit will not feel the same in August. Research on micro-modal knits has also looked at how elastane content and finishing affect drying [8]. So look at weight and feel, not just the fibre label.
What about elastane?
A small share of elastane (spandex) gives stretch and shape recovery, so the leg stays in place instead of riding up. Almost all boxer briefs use some.
How we chose our fabric
We wanted one fabric for a whole Gulf day: the car park, the office, the mall, prayer, the drive home. We chose 93% MicroModal and 7% elastane, in a light knit with flatlock seams. It is not the fastest-drying fabric in the gym, and we say so. For everyday heat it is the balance we would choose. See the Originals 7″ and the 9″ Long, or find your length in the boxer brief length guide. Wearing a thobe or kandura? Read what to wear under a kandura or thobe. Training? See underwear for the gym in Dubai.
FAQ
Is MicroModal better than cotton in hot weather?
For all-day wear, usually yes. Modal takes up more moisture than cotton (about 11.8% vs 7–8% moisture regain) and moves it quickly, while cotton knits can stay damp. Cotton is still fine on cooler days.
Does MicroModal dry faster than polyester?
No. Polyester absorbs very little water (about 0.4% moisture regain), so thin polyester knits dry faster. MicroModal is chosen for absorbency and softness, not for the fastest drying.
Is bamboo underwear really bamboo?
Usually not. Most is viscose (rayon) made from bamboo pulp. The US Federal Trade Commission says it should be labelled as rayon or viscose made from bamboo.
What is the difference between modal and MicroModal?
MicroModal is modal made as finer fibres, which gives a smoother, softer fabric.
What fabric is best under a thobe or kandura?
A light, soft fabric that handles moisture, such as modal or MicroModal with a little elastane, in a 7″ or 9″ length so it stays in place.
Sources
- "Properties, Production, and Recycling of Regenerated Cellulose Fibers: Special Medical Applications", PMC (open access), fibre property table (moisture regain: cotton 7–8%, viscose 11–14%, modal 11.8%). https://pmc.ncbi.nlm.nih.gov/articles/PMC11595832/
- Ahmad, H.S. & Jamshaid, H. (2019), "Development of Thermo-Physiologically Comfortable Knit Structure for Sports Application", Tekstil ve Konfeksiyon 29(2) (polyester 0.4%, cotton 8.5% moisture regain; modal ~50% more hygroscopic per unit volume than cotton). https://doi.org/10.32710/tekstilvekonfeksiyon.570700
- "Thermal and Moisture Management Properties of Knitted Fabrics for Skin-Contact Workwear", PMC (open access) (drying: thin polyester/elastane ~3 min; cotton-rich underwear fabric ~25 min; density vs moisture transfer). https://pmc.ncbi.nlm.nih.gov/articles/PMC12029065/
- Lenzing, modal fibre product page ("Micro technology… the finest fibers", moisture absorption and release). lenzing.com, modal fibre page
- Suganthi, S. & Pachiayappan, K.M. (2023), Journal of Natural Fibers 20(1) (modal wicks and spreads moisture in ~50% less time). https://doi.org/10.1080/15440478.2022.2131685
- US Federal Trade Commission, Bamboo textiles. https://www.ftc.gov/bamboo-textiles
- US Federal Trade Commission, "How to Avoid Bamboozling Your Customers". https://www.ftc.gov/business-guidance/resources/how-avoid-bamboozling-your-customers
- Gocek, I. (2019), "Synergistic effects of chemical finishing processes on comfort characteristics of micro-modal and lyocell knitted fabrics", Materials Testing 61(3) (drying rate; elastane and finishing effects). https://doi.org/10.3139/120.111312