Molecular Mass/ Weight of Polymers

ð  For many reasons, particularly to know more about polymer molecular systems, it is necessary to characterize them with respect to

(i)      The chemical identity of their repeat units,

(ii)     Nature of end groups present,

(iii)   Existence of branching with nature of branch units and their frequency,

(iv)    Presence of comonomer units and also copolymer composition and comonomer sequence distribution in copolymer systems,

(v)     Solubility and associated features,

(vi)   Optical properties covering clarity or degree of clarity and refractive index, R

(vii) Resistance properties with reference to thermal, mechanical and electrical resistances, photoresistance or photostability, chemical and weather resistance, corrosion resistance, and also bioresistance or resistance to biodegradation.

ð  But what is more important and fundamental is knowledge about the molecular weight of a given polymer.

ð  For molecular weight determination, it is necessary to dissolve the polymer in an appropriate solvent and begin with a dilute solution.

ð  It is very difficult to determine the molecular weight of polymers because the molecules in polymeric chain vary considerably.

ð  Therefore, the molecular weight of any polymer is determined as average values.

·         Number Average Molecular Weight (Mn)

·         Weight Average Molecular Weight (Mw)

   

Number Average Molecular Weight (Mn)

ð  It is based on number of molecules in polymeric chain.

ð  It is defined as multiple of total number of monomer (or repeating unit) with its molecular weight divided by total number of monomers.

Where, N_i = Number of moles of molecules

 M_i = Molecular weight of the repeating unit (or 1monomer)

ð  It can be determined by end group analysis, osmometry method, cryscopy and ebull ioscopy.

Weight Average Molecular Weight (Mw)

ð  It is based on the weight of monomers.

ð  It is defined as summation of multiple of molecular weight of chain length and weight of molecules of chain length divided by total weight of molecule of chain length.

Where, N_i = Number of moles of molecules

                                     M_i = Molecular weight of the repeating unit (or 1monomer)

                                     W = Weight of polymers;  w_i = Weight of molecules           

ð  It can be determine by viscosity method, light scattering method and ultracentrifugal method.

Classification of Polymer

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Sublimation Fastness Tester

Sublimation Fastness Tester is a suitableinstrument for dyestuff manufacturers as well

as textile processors for checking effects ofdry heat on dyestuff.            

                       

ð  Sublimation fastness and staining effect properties of individual dyes can be tested at various temperatures.

ð  In a single test, entire range of effective temperature can be tested. The heating pads are made up 
      of hard chromed electrolyte copper for even and quick distribution of heat.

A = Upper Pad (With Undyed Fabric)

B = Specimen Pad

C = Temeprature Indicator (Digital)

Features of Sublimation Fastness Tester:

ð  Testing the effect of direct heat on the dyestuff.

ð  120°C up to 250°C temperature range.

ð  10 to 60 seconds contact timer.

ð  Individual temperature controllers with sensors.

Specifications of Sublimation Fastness Tester:

Temperature range for test	: 120°C up to 250°C
Temperature settings	: 150°C, 180°C & 210°C on each pad or variable temp setting.
Power readout	: Digital display for each pad.
Size of each pad	: 40 mm x 100 mm.
Timer range	: 10-60 sec.
Working

ð  A dyed cloth piece is sandwiched between two undyed pieces and placed to cover the heat pads and the test goes on for a pre-set time period.

ð  The fabric pieces should be picked up immediately. The undyed fabric pieces will be stained by the dyes.

ð  This gives the sublimation fastness properties for the range of temperature 130°C to 250°C in one test.

 ð  A ready comparison of sublimation fastness properties at various temperatures is hence available.

Perspiration Fastness Tester

PERSPIROMETER

Perspirometer is used for determining the resistance of the colour of textiles of all kinds and in all forms to the action of human perspiration. 

ð Colour fastness of dyed or printed fabrics, against perspiration, is determined by exposing the fabric to the action of both alkaline and acidic reagents, while in contact with undyed adjacent fabrics on both sides.

Features of Perspirometer:

ð  Can also be used for testing colour fastness against sea water and water.

ð  Made of stainless steel frame.

ð  User friendly and corrosion resistant.

ð  Smooth precision engineered components for excellent performance.

Specifications of Perspirometer:

Frame Construction	: Stainless steel
Load on the Test Specimen	: 5 kg.
Size of Test Specimen	: 100 mm x 40 mm
Size of Acrylic Separator Plates	: 115 mm x 60 mm

Working

ð The test specimen is dipped in alkaline solution a liquor ratio of 50:1 and allowed to remain in the solution at room temperature for 40 minutes. The excess liquor is drained and the composite specimen is placed between the 2 acrylic separator plates.

ð Similarly the second composite specimen is made wet.

ð After loading the entire test specimen as above, acrylic separator plates are stacked one over the other and all these are placed in between the 2 loading stainless steel plates.

ð The loaded apparatus is placed inside a thermostatically controlled incubator maintained at 37°C for 4 hours.

ð Once the time is over, the apparatus is removed from there and the acrylic plates are removed with the composite specimens from the apparatus.

ð The test specimen is separated from the adjacent fabric and evaluated for:

1.      The change in colour of the test specimen.

 2.   The degree of staining of the white the 2 pieces of adjacent fabrics. They are evaluated using  
       grey scales.

Washing Fastness Tester

LAUNDER – O – METER

ð  The colour fastness of textile material is determined by way of mechanical hesitation of a specimen of textile with the piece of specified adjacent fabrics in Standard Soap Solution followed by rinsing and drying. 

ð  Thereafter, the change in colour of specimen and stains of the adjacent fabrics are assessed with standard grey scale.

Launder – o – meter is used widely for determining colour fastness of textile materials to washings. 

Features of Launder – o – meter:

ð  It is fabricated out of quality stainless steel.

ð  Possess electric heater to heat water in water bath.

ð  The microprocessor based programmer is provided for temperature control.

 ð Buzzer to indicate the completion of the process cycle or step.

Specificationsof Launder – o – meter:

Beakers (Test Vessels)	: Leak-proof Beakers with Gaskets
Standard Seal for Beakers	: Special Neoprene Gaskets
Speed of Rotation	: 40±2 rpm
Temperature Controller	: PROGRAMMABLE MEMORY BASED DIGITAL
Temperature Regulation	: PT-100 with ±2.0°C (As per I.S.O.)
Timer (Digital)	: 0-99 Minutes
Motor	: Single Phase, Geared Motor 220 Volt AC

Working

ð Precondition the main bath, choosing the temperature and time suitable for the test.

ð Fill each jar with necessary amount of Standard Soap Solution to give a liquid to composite specimen ratio of 50: 1.

ð Assuming the temperature is attained, set the timer depending on your test.

ð Open the beakers and place one composite specimen in each jar containing test liquid. Fit the beakers to their respective position by pressing against the spring and rotating it.

ð Press the start switch. After the set time is reached, the motor stops automatically with an alarm buzzer.

ð Remove all the beakers and take out the Composite Specimens and SS balls with the help of filter unit.

ð Rinse the Composite Specimen twice in cold water and then in running tap water for 10 minutes and squeeze them.

ð Evaluate the change in colour of the treated test specimen in comparison with an untreated piece of the same sample using the Standard Grey Scale for evaluation of change in colour.

Rubbing Fastness Tester

CROCKMETER

ð  In addition to colour transference tests, the Crockmeter performs scuffing, wet / dry abrasion, flexing, powdering, dry-cleaning, ink abrasiveness, and other tests.

ð  Test conditions are controlled and reproducible through the use of standard pressure and motion.

Features of Crockmeter:

ð To determine the Colour Fastness of Textiles.

ð The equipment consists of a counter.

ð It is provided with a flat peg.

ð It also consists of an operating handle.

ð Tests the colour fastness of the textile in a very accurate manner.

ð It gives not only accurate but quick results also.

Specifications of Crockmeter:

Diameter of the Rubbing Finger	: 16 mm & 25 mm
Force on the Finger	: 9 N & 20 N
Size of Crocking Cloth	: (5 x 5) Cms& (7 x7) cms
Length of the Traverse	: 100 ±5 mm
Size of Test Specimen	: 25 x 5 Cm
Working

Ø  Dry Rubbing:

ð  Properly mount your specimen and test cloths.

ð  The counter has to be reset by moving the knob on the left side of the counter.

ð  The finger is positioned on the specimen at the base’s front end and handle is rotated in the clockwise direction at the rate of approximately 1 revolution per second.

ð  The handle is then rotated equal to the number of strokes specified by the test method.

ð  When the desired number of strokes is reached, the crocking cloth is removed from the finger and its degree of staining has to be evaluated by SDC grey scale.

Ø  Wet Rubbing:

ð  A fresh piece of crocking cloth is soaked in distilled water and the excess water is removed so that it contains its own mass of water.

ð  The wet piece of the crocking cloth is fixed over the end of the finger of the Crockmeterand the test is undertaken.

ð  The dyed or printed fabric has to be mounted on a lower platform.

ð  Then 10 cycles are rubbed with a white fabric, which is mounted on a peg in the upper rubbing arm. 

ð  Then the extent of colour that rubs away onto the white fabric against a colour transference scale has to be determined. 

ð  The rubbing action of the peg+ enabled fibers from the upper coloured flannel fabric surface to be transferred onto the white backing fabric mounted on the lower platform.  The cloth is then removed to evaluate the discolour level in comparison with a gray-scale.