Determination of Hydroxyl Value in Polyols and Acrylic resin

Determination of hydroxyl value in polyols, like PGG-400, Polyterathne-1000, and emulsifier by acetic anhydride methods and by using Acetylating Reagent.

APPARATUS

a). Magnetic Stirrer

b). Water Bath.

c). Pipette, 20ml.

d). Burette, 50ml

e). Conical flasks, 250ml

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REAGENTS

a). Acetic anhydride, Purity-99.0%

b). Pure pyridine-Colorless, Purity-99.5% (% moisture-less than 0.10%)

c). 0.5N NaOH Solution

d). Phenolphthalein Indicator.

e). Acetylating Reagent

Preparation of Acetylating Reagent

Take 12.7 ml of the acetic anhydride in a stoppered flask with a pipette. 

Add 100ml of pyridine into it. Shake well, and make the fresh solution of acetylating reagent while carrying out the test.)

Procedure of Hydroxyl Value

1). In a 250ml stoppered conical flask take sample weight. The sample weight is to be taken on a 100% solids basis as per the following

Wt. of the sample Hydroxyl Number

7.0 Less than 40

6.0 up to 80

5.0         100

4.0         120

3.0         150

2.0         200

2). Pipette 20ml of the acetylating reagent to the flask in which sample(S) is taken, at the same time add a similar volume of 20ml of acetylating reagent to another flask containing no sample for Blank(B).

3). Stopper the flasks and swirl them on a magnetic stirrer until the sample is completely dissolved.

4). Place both flasks as close together as possible in the water bath at 98±2°C for 2 hours. Keep enough water in the water bath to cover the level of liquid in the flasks.

5). Remove the flasks from the water bath and allow them to cool at room temperature.

6). Carefully rinse the walls of both flasks with 20-30ml of DM- water.

7). Add 2-4 drops of phenolphthalein indicator and titrate immediately with 0.5N NaOH solution till the faint pink color persists for 30 seconds. The solution should be swirled during the titration, with vigorous swirling as the endpoint is reached. 

8). Carry out Blank similar way without taking the sample.

CALCULATION Formula of OH Value:

HYDROXYL NUMBER = (B – S) x N x 56.11

Weight of sample

B=ml of NaOH required by blank

S= ml of NaOH required by the sample

N=Normality of NaOH

  Acetic acid testing |  Testing of Purity of glacial acetic acid

DETERMINATION OF HYDROXYL VALUE BY BENZENE METHOD

APPARATU

a). Magnetic Stirrer

b). Magnetic Bead

c). Pipette, 20ml.

d). Burette, 50ml

e). Conical flasks, 250ml

f). Air condensers bulb type

g). Heating Mantles, 250ml flask size

REAGENTS

a). Acetic anhydride (Purity-99.0%)

b).Pure pyridine-Colorless (Purity-99.5% (% moisture-less than 0.10%)

c). 1N KOH Solution

d). Phenolphthalein Indicator.

e). Acetylating Reagent

Preparation of Acetylating Reagent: Take 20 ml of the acetic anhydride in a beaker and add 60 ml of pyridine into it. Shake well, and make the fresh solution of acetylating reagent while carrying out the test.

PROCEDURE

1). In 250ml stopper conical flask weigh 1-2 gms of Sample and add 20ml acetylating reagent into it.

2). At the same time add a similar volume of 20ml of acetylating reagent to the other flask containing no sample for Blank(B).

3). Now reflux the contents of both the flasks in heating mantles for 60 minutes with air condensers.

5). After 60 minutes rinse the walls of condensers with 20ml of benzene to dissolve any insoluble material.

6). Cool the conical flasks along with the condenser and add 50ml of DM water through the condenser.

7). Titrate the free Acetic Acid with 1N KOH using Phenolphthalein indicator 2-4 drops until the color changes to light pink.

CALCULATION

(A) HYDROXYL (OH)VALUE = (B – S) x N x 56.11+Acid Value

Weight of sample

B=ml of KOH required by blank

S= ml of KOH required by the sample

N=Normality of KOH

(B) ON SOLID BASIS = OH Value x 100/SOLID

(C) OH Content = (B – S) x N x 17 x 100 = (B – S) x N x 17 =(B – S) x N x 1.7

1000 x Weight of sample 10 x Weight of sample Weight of sample

(D) % of OH = OH Value x 17x 100

•                                 56100

(E) OH Equivalent = 17 x 100% of OH

DETERMINATION OF GEL TIME FOR MODIFIED ACRYLIC RESIN 

APPARATUS:

A). 100ml Beaker

B). Digital Thermometer

C). Heating Mantle for heating

REAGENTS

A). Sample of Modified Acrylic Resin

B). T.B.P.B. Solution

GEL TIME PROCEDURE

A). Take the Modified Acrylic Resin Sample in a beaker and put it into a heating mantle for heating.

B). Now dip the digital thermometer into it and continue stirring the solution with this thermometer.

C). When the temperature reaches up to 60˚C, add T. B. P. P. 1.3% of Modified Acrylic Resin Sample.(e.g. 40 gm Modified Acrylic Resin sample and its 1.3% is 0.52 gm TBPB sample) under stirring.

D). Now at the same time start a stopwatch and note the time at which the sample becomes GEL, at the same time note down the thermometer reading also.

E). Now also remove the thermometer fast from the sample otherwise it sticks to the gelled sample.

F). This is the GEL TIME at (_____˚ C) i.e. approx 115±5 ˚ C (Solidify Gel)

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