Lecture 9 - Textile fibers examination part 2

For man made fibers, distinction must be made between

-synthentic
- regenerated

What are synthetic fibers?

Manufactured from polymers deriving from simple starting materials (coal and oil)

What are regenerated fibers?

Manufactured from naturally occurring polymers (cellulose)

What are two examples of semi synthetic fibers?

- acetate and rayon

What are examples of synthetic organic fibers?

- polyester
- nylon
-acrylic
- polyolefin

Most synthetic fibers are produced by what process

melt spinning process

What determines the properties of the fibers and can serve as a signature of a particular manufacturer in the melt spinning process?

The shape and dimensions of spinneret

What type of fibers are usualy used for carpets?

Trilobal fibers

What is luster?

Degree of light that is reflected from the surface of a fiber or the degree of gloss or sheen that the fiber possesses

What are delusterants?

substances that reduce the luster of synthetic fibers

When light shines on a fiber, it will be BLANKKK transmitted, absorbed, or reflected depending on the structure of the fiber and the wavelength of light.

partially

Which type of anisotropic materials are man made fibers?

uniaxial anisotropic materials that have 2 RIs perpendicular to each other

How are the refractive indexes of man-made fibers directed?

One is directed toward the length of the fiber and the second is parallel to it

How are light rays passing through an anisotropic material act/

They are deviated differently and travel at diff propagation speeds

What angle gives the maximum brightness orientation for fiber sample?

45 degrees

If inteference colors are absent then the fiber will appear ?
What strength/birefringence will it have?

white or gray
weak birefringence

If interference colors are present, what birefringence will be present?

medium-high

Dichroism is the

variation in the absorption of radiation by a colored fabric with the direction of polarization of light

t or f
The resulting color is very often the most variable
characteristic of textile fibers.

true

functions of colorant molecule

- adjustment of color
- physical character

Main classification scheme typically used by forensic chemists is based on

method of dye application.

Use of IR common to identify

fibers composition, not fiber dye.

Raman microspectroscopy is well suited

analysis of colored fibers.