Monday, November 23, 2009

NEMO Classroom Lessons #164: Nylon vs Polyester

“What’s the difference?”, you might ask. Nylon and polyester are used throughout the outdoor industry. Since both are synthetic polymers that have existed long before our time, most people don’t think twice about using one versus another. Since fabrics can be ‘finished’ in different ways to increase strength, UV protection, waterproofness, etc., the differences I’m talking about here relate more to the base fabric. Here’s a useful guide to key differences that might make you stop and think about fabrics the next time you’re looking at gear.

It’s not a fair comparison to say that Sugar Ray Robinson, a welterweight (140-147 lbs) is less strong than Evander Holyfield (heavyweight at >200 lbs). In same way, we generally try to compare fabrics ‘pound for pound’ – meaning that they are at the same denier (fineness of fiber). At the same denier, nylon tends to be a stronger than polyester and the difference can be such that a 420D nylon is stronger than 600D polyester. The strength difference shows up when you’re examining tear, abrasion resistance, or something as simple as the fabric’s ability to hold stitches. Since polyester is weaker than nylon, the thread count (and thus weight) can often be higher in polyester at the same denier.

The Cruel Sun
Seems pretty clear cut right? Nylon is stronger… except that in the presence of UV, it will break down and start to degrade much faster than polyester. Polyester naturally inhibits UV. Although the fiber may be weaker at the start, it holds up better over time.

Moisture, Stretch, and All That Good Stuff
Nylon tends to absorb more moisture than polyester. This means that if it rains, you’ll probably lose the perfect tension you had when setting up your tent. Polyester is more resistant to stretching/shrinking than nylon because it won’t take in as much water. In wet weather with polyester, you’ll generally be carrying less moisture which translates into faster drying times.

Dye Transfer
Nylons tend to be easier to dye than polyesters. The majority of dye migration problems I’ve seen have been with polyester. Wet/Damp conditions with polyester can definitely lead to dye migration, especially with darker colors.

Green Concerns:
Right now, nylon is more difficult to recycle than polyester. There are many ways to turn in old polyester for recycling, but very few for nylon. Nylons break down into toxic and hazardous material when melted, and incinerating them to recover the high cost of energy used to make them is expensive.

The decision to use polyester or nylon is almost never clear cut. There's a lot of strategery in adding finishing/coating/lamination methods that help improve performance (and hopefully don't adversely affect other properties). Hopefully, this will give you a good sense of tradeoffs that gear designers go through when selecting materials for use.


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