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Name: Arye
Status: other
Grade: 12+
Location: IL
Country: USA
Date: Summer 2011


Question:
Polypropylene, polyester, or Nylon webbing. How can one tell the difference between them when no label is supplied. Are there solvents one can use to separate one from another in the group? I understand there differences in the stretch rate Polypropylene, polyester, stretch less than Nylon, Nylon stretching the most. Polyester is the most UV resistant. All are hydrophobic to various degrees polypropylene, polyester than nylon being the least. Polypropylene, polyester, or Nylon webbing. How can one tell the difference between them when no label is supplied.



Replies:
Hi Arye,

The short answer to your question on how to tell these polymers from each other is "with considerable difficulty"! None of the three polymers you mention (polypropylene, nylon, and polyester) are soluble in any solvents, so detection by solvency is not possible. None of the rest of the properties you mention (stretch rate and hydrophobic properties) produce sufficiently clear cut results to be useful. One semi-reliable way to tell them apart is by the smell that results from heating a small sample. Polyolefins such as polypropylene (and polyethylene) smell like heated wax (since these polymers are in essence simply long chain waxes). Nylons also tend to have their own distinctive odor when heated.

In the case of nylon (polyamide), things get even more annoying. There are two common types of nylon with their own distinctive characteristics, namely Nylon 6 and Nylon 6,6 and they are chemically different from each other. There is no simple way to tell them apart.

Moisture absorption is one possible way to tell your three examples apart. Nylon has by far the greatest moisture absorption (from 2% to 9%). Polypropylene absorbs none whatsoever, and polyesters typically absorb less than 1%. The final way to tell these polymers apart is to look at them. While not totally reliable, an experienced person can usually manage to identify these polymers reasonably reliably.

Regards, Bob Wilson


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