The links provided above are a good overall description of the qualities of the different fibers but, There is only one way in the field to determine what any particular fiber is made from and that is with a burn test.
This is what a forensics lab would use to determine unknown fiber content if hey do not have access to a spectrum analyzer or the set for the TV show.

This is the link to the table I am quoting below, for those interested.
http://craftydaisies.com/2007/04/04/fabric-burn-test/

How to determine fabric content by using the burn test.

Snip a piece of fabric equivalent to 1″ square.(If you've done a couple of these tests before or you have a good idea what your working with before hand it can be done with as little as one strand of fiber.)
Using a butane lighter and holding the fabric with a pair of tweezers ignite the fabric over a non-flammable surface in a well ventilated area.Examine the quality and color of the flame, the odor produced, and the quality of the resulting ash or cinder. Use this table to help determine your fabric’s content.

FABRIC
WOOL

FLAME QUALITY
orange color sputtery

ODOR
burning hair or feathers

ASH QUALITY
blackish turns to powder when crushed

COMMENTS
flame will self extinguish if flame source is removed no smoke

FABRIC
SILK

FLAME QUALITY
burns slowly

ODOR
burning hair or feathers

ASH QUALITY
grayish turns to powder when crushed

COMMENTS
burns more easily than wool but will self extinguish is flame source removed

FABRIC
COTTON

FLAME QUALITY
yellow to orange color steady flame

ODOR
burning paper or leaves

ASH QUALITY
grayish, fluffy

COMMENTS
slow burning ember

FABRIC
LINEN

FLAME QUALITY
yellow to orange color steady flame

ODOR
burning paper or leaves

ASH QUALITY
similar to cotton

COMMENTS
takes longer to ignite than cotton but otherwise very similar

FABRIC
RAYON (Viscous)

FLAME QUALITY
fast orange flame

ODOR
burning paper or leaves

ASH QUALITY
almost no ash

COMMENTS
ember will continue to glow after flame source removed

FABRIC
POLYESTER

FLAME QUALITY
orange flame, sputtery

ODOR
sweet or fruity smell

ASH QUALITY
hard shiny black bead

COMMENTS
black smoke

FABRIC
ACETATE

FLAME QUALITY
burns and melts,sizzly

ODOR
acidic or vinegary
hard black bead will continue to burn after flame source removed

FABRIC
NYLON

FLAME QUALITY
burns slowly and melts, blueish base and orange tip, no smoke

ODOR
burning celery

ASH QUALITY
hard grayish or brownish bead

COMMENTS
self extinguish if flame source removed

FABRIC
ACRYLIC

FLAME QUALITY
burns and melts, white-orange tip, no smoke

ODOR
acrid

ASH QUALITY
black hard crust

COMMENTS
will continue to burn after flame source removed


In short:If you only want to use a single strand of fiber from your kilt, smell is the best indicator of whether your kilt is made from, P/V or Acrylic.
P/V will have a smell like burning leaves & apples.
Acrylic will smell sharp and bitter like acid.


Because there is one other factor in determining what your next kilt will be made of, I am also including a rough estimate of the relative cost of the fibers on todays market.

Most expensive

1) Hemp
2) Silk
3) Wool
4) Linen
5) Cotton
6) Polyester
7) Rayon(Viscous)
8) Nylon
9) Acetate
10) Acrylic

Least expensive