3. DENSITYDENSITY
Density is the measure of the
“compactness” of a material
How close the atoms or molecules are to
each other
More than “heaviness” - density includes
how much space an object takes up.
All substances have density including
liquids, solids, and gases
5. DENSITYDENSITY
What is Density?
If you take the same volume of different substances, then
they will weigh different amounts.
1 cm3
Iron has the greatest mass and therefore the most dense
Wood
0.50 g
Water
1 cm3
1.00 g
Iron
1 cm3
8.00 g IRON
6. DENSITYDENSITY
D = m/v (g/cm3
)
Mass usually expressed in grams
Volume usually expressed in cm3
or liters,
etc.
7. DENSITYDENSITY
Density = amount of matter per unit volume
Density is the ratio of mass to volume
If the volume stays the same and the
mass increases . . . the density will
increase
If the mass stays the same and the
volume increases . . . The density will
decrease
8. FIBRE DENSITYFIBRE DENSITY
Fibre density plays a direct part in affecting the weight of
fabrics, so that glass fabrics, with a fibre density of 2.56, will
tend to be heavy, whereas those of polyethylene, with a
density of 0.92 will be light.
Fibre density is a useful parameter in fabric identification and
occurs incidentally in many parts of textile physics.
For some purposes, it is more convenient to use specific
volume, which is the reciprocal of density and is expressed in
cubic centimeters per gram.
9. FIBRE DENSITY MEASUREMENT – Simple MethodFIBRE DENSITY MEASUREMENT – Simple Method
ρ = m = 01 =10.0 g/cm3
V 0.1
* Find the Mass of the fibre on a* Find the Mass of the fibre on a
balance.balance.
* Fill the Measuring Cylinder with* Fill the Measuring Cylinder with
liquid to a known Volume.liquid to a known Volume.
* Add the Object.* Add the Object.
* Work out the Volume of liquid* Work out the Volume of liquid
that is displaced.that is displaced.
*Calculate the Density based on*Calculate the Density based on
displacement of the level of liquiddisplacement of the level of liquid
in a measuring cylinder equals thein a measuring cylinder equals the
volume of the added fibres.volume of the added fibres.
0.1 cm3
0.2 cm3
m =1g
10. FIBRE DENSITY MEASUREMENT – Simple MethodFIBRE DENSITY MEASUREMENT – Simple Method
Two fundamental forces of error are immediately obvious.
Firstly, the liquid may not displace all the air particularly from
crevices in the fibre surface. This means that the measured
volume will be too high and the density too low.
Secondly, the liquid may be absorbed by the fibres, which
results in a smaller displacement of the liquid level. This
would give too low a volume and too high a density.
It is now generally accepted that the best values of density
are obtained with a large number of organic liquids such as
nitrobenzene, olive oil, toluene,benzene and CTC.
This method is sound in principle, but it would not be very
accurate in practice.
11. FIBRE DENSITY MEASUREMENT – Floatation MethodFIBRE DENSITY MEASUREMENT – Floatation Method
This method was developed by Abbott and Goodings.
This method is prefered for single fibre or small bundles of fibres.
The chopped-up fibres are placed in a liquid (or a mixture of liquids)
of the same density as the fibres, and then centrifuge in a tube, they
remain as a uniform cloud.
If the densities are different, they will be accumulated into a single
group, which floated if the fibre density is the lower and sank if it is
the greater.
By a process of trial and error, the correct density can be calculated.
Note :
Centrifuge means : a machine with a rapidly rotating
container that applies centrifugal force to its contents,
typically to separate fluids of different...
12. FIBRE DENSITY MEASUREMENT – Density Gradient Tube MethodFIBRE DENSITY MEASUREMENT – Density Gradient Tube Method
In this method a long tube called density gradient tube
containing a heavy liquid (Eg. Pentacholoethane,1.7g/cm3) at
the bottom, a light liquid (eg. Xylol, 0.9 g/cm3) at the top, and
a continuously varying mixture of the two between them.
If the fibres dropped in, they sink to the point at which the
fibre density equals the liquid density and remain suspended
there.
Calibration of the tube may be provided either by means of
pieces of different materials of known densities floating at
their appropriate levels or by hollow glass spheres of varrying
mean density.
The fibre density can be found by interpolation between the
known densities on either side of the position at which the
fibres come to rest.
13. FIBRE DENSITY MEASUREMENTFIBRE DENSITY MEASUREMENT
In Textile Industry QC dept is responsible to carried out
various types of quality test. Density test is one of them.
Density is important for fabric manufacturing.
Density of a textile fiber is important to know.Density is
mreasured by the following steps. Density gradient is
prepared as the following.
* Clamp the density gradient glass in a firm vertical stand.
* Pour into the tube 25 ml of tetrochloroethylene.
* Now prepare mixture of xylene and tetrachloroethylene
in
descending order of percent tetrachloroethylene
90/10,80/20,70/30,60/40,50/50,40/60,30/70,20/80 and
10/90.
* Pour 25ml of each in order carefully down the side of the
gradient tube.
* Finally put 25 ml of xylene on top.
14. FIBRE DENSITY MEASUREMENTFIBRE DENSITY MEASUREMENT
* Take short fragments of dyed reference fibres and tie in a
knot snipping off loose ends.
* Boil for 2 minute in xylene solvents to remove moisture and
air.
* After about a half hour they should come to the rest in a level
representing their density.
* Calibrate glass sphere may be used to determine the actual
density at various levels.
* Prepare the unknown fiber in like manner, place in the
gradient coloumn and note at what level it flots.
So, that’s all about the density test. We can test the various
types of fibers density as the above procedure.
15. Values of the Densities and Specific VolumesValues of the Densities and Specific Volumes
Fibre Density g/cm3) Specific Voloume cm3/g)
Dry 65% RH Dry 65% RH
Cotton (Lumen
filled) 1.55 1.52 0.64 0.66
Viscose Rayon 1.52 1.49 0.66 0.67
Secondary
acetate, triacetate 1.31 1.32 0.76 0.76
Wool 1.30 1.31 0.77 0.76
Silk 1.34 1.34 0.75 0.75
Casein 1.30 1.30 0.77 0.77
Nylon66 & Nylon 6 1.14 1.14 0.88 0.88
Terylene & Other
Polyester 1.39 1.39 0.72 0.72
Orlon & Other
acrylic fibres 1.19 1.19 0.84 0.84
16. Values of the Densities and Specific VolumesValues of the Densities and Specific Volumes
Fibre Density g/cm3) Specific Voloume cm3/g)
Dry 65% RH Dry 65% RH
Polypropylene 0.91 1.09
Polyethylene LD 0.92 1.09
Polyethylene HD 0.95 1.05
Dynel (Mod
acrylic) 1.29 1.29 0.78 0.78
Teklan (Mod
acrylic) 1.34 0.75
Poly Vinyl chloride 1.40 0.71
Poly Tetra Fkuro
Ethylene 2.20 0.45
Glass 2.50 2.50 0.40 0.40
17. DENSITY AND ORDERDENSITY AND ORDER
Density Measurement is commonly used as a means of
estimating the degree of order, or crystallinity of fibres. The
necessary relation is given as equation.
Degree Of Order = ρ - ρam
ρcr - ρam
* The fibre density ρ is measured by the methods discussed.
* The crystal density ρcr, can be calculated from the
dimensions of the unit cell, determined from the x-ray
diffraction pattern and the molecular weight.
