Density Gradient Measurement

VP.Senthilkumar

11MT71

DENSITY DENSITY

What would take up more space??? A kilogram of feathers…..

or a kilogram of steel??

DENSITY DENSITY Density is the measure of the

“compactness” of a materialHow close the atoms or molecules

are to each otherMore than “heaviness” - density

includes how much space an object takes up.

All substances have density including liquids, solids, and gases

DENSITY DENSITY

“Compactness”

DENSITY DENSITY

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

1

Wood

0.50 g

Water

1 cm3

1.00 g

Iron

1 cm3

8.00 g IRON

DENSITY DENSITY

D = m/v (g/cm3)

Mass usually expressed in grams Volume usually expressed in cm3 or

liters, etc.

DENSITY DENSITY 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

FIBRE DENSITY FIBRE 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.

FIBRE DENSITY MEASUREMENT – Simple Method FIBRE DENSITY MEASUREMENT – Simple Method

= 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 liquid displacement of the level of liquid in a measuring cylinder equals the in a measuring cylinder equals the volume of the added fibres.volume of the added fibres.

0.1 cm3

0.2 cm3

m =1g

FIBRE DENSITY MEASUREMENT – Simple Method FIBRE 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.

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...

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.

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.

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.

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

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

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 = - am

cr - am

* The fibre density is measured by the methods discussed.

* The crystal density cr, can be calculated from the

dimensions of the unit cell, determined from the x-ray

diffraction pattern and the molecular weight.

Thank you!Thank you!