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Textile Analysis(Natural or chemical fiber?)

Our everyday clothes are made of natural and/or chemical fibers.

Differences between natural and chemical fibers

Natural fibers come from plants (e.g., cotton and hemp, which consist of cellulose) and animals (e.g., silk, wool, and fur, which consist of proteins). The characteristics of these fibers are:

  1. No uniform shape
  2. Weak resistance against acids and alkalis but strong

resistance against organic chemicals (e.g., acetone and metacresol)

Most chemical fibers are synthetic and come from plastics (e.g., nylon, polyester, and acryl) and recycled fibers from natural fibers by chemical processing (e.g., rayon and copra). The characteristics of these fibers are:

  1. In most cases, uniform shape
  2. Strong resistance against acids and alkalis (synthetic fibers) and against organic chemicals (recycled fibers, except for acetate)

[ What to do with a textile of an unknown material: ]

The content of a fiber can be checked by applying the above property differences.

For example, if sulfuric acid of 70% concentration is applied to a textile made of polyester and cotton, the cotton dissolves but the polyester does not. Therefore, measuring the remaining fibers clarifies the mix ratio of polyester and cotton. In other words, we can analyze a textile made of different fibers by adding sulfuric acid and other chemicals.

[ Let's try a test. ]

This is a piece of cloth of an unknown material. Let's analyze the cloth with sulfuric acid to see whether it is made of a natural fiber or a chemical fiber.

Picture 1
1. Put a piece of the cloth in the flask.

Picture 2

Picture 2-2
2. Pour in some sulfuric acid and gently shake the flask.

Picture 3
3. The piece of cloth has totally dissolved.

Now that the cloth has dissolved in the sulfuric acid, we know that it was made of cotton (natural fiber).

[ Even fibers of the same chemical material can be distinguished. ]

For example, cotton and rayon are both made of cellulose. We cannot distinguish them by chemical analysis alone, but can clearly see the difference under an electron microscope.

[ We can distinguish the materials under an electron microscope. ]



Cotton fibers are twisted and their shapes are not uniform. Rayon fibers show lines in one direction and they have a uniform shape.

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