Synthesis Of Visco Elastic Foam Biology Essay

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In Laboratory visco-elastic foam can be prepared using a standard hand mix procedure. On lab scale cup foaming is sometimes called as hand mixing. So, here cup foaming is used as a synthesis technique for preparing visco-elastic foam on lab scale.

4.1.1 Cup Foaming

Cup foaming is a simple technique to prepare foam on lab scale. It is also used to evaluate the foaming systems to compare raw materials and resulting foam properties. [2] The list of equipment required for cup foaming is:

Good results are obtained by keeping foaming systems and environment at constant temperature. [2]

4.1.2 Steps of Cup Foaming [2]

Following steps are followed in cup foaming to synthesize foam by this foaming process:

Weigh the quantity of polyol in a plastic or paper cup by using electronic weight balance.

Then add catalyst, water, blowing agent and surfactant (if used) in it with gentle stirring with spatula. If tin catalyst is used then it is added as a last step of addition to prevent its hydrolysis.

Weigh the polyisocyanate component in a separate cup using electronic weight balance.

Pour the polyisocyanate component into the cup containing polyol and thoroughly mix it for 5 seconds.

Allow the foaming mixture to expand and rise in the same cup or pour it into the separate container.

Measure cream, rise and gel times.

Cure the foam block at room temperature overnight. Cut the foam samples for testing from upper parts of the foam cured.

Cream time: The time interval at which mixture turns creamy and starts to expand. It is the bench time of mixing and usually measured in seconds.

Gel time: The time interval at which mixture turns into the foam of a gel and it is due to the cross linking reactions occurring in the mixture. To test for gel touch the foaming mixture with spatula, a thread will form between spatula and foam. It is also measured in seconds.

Rise Time: The time interval at which mixture starts to rise up. It can be in minutes or seconds depending upon the type of foam synthesized.

4.2 Chemicals required for Viscoelastic foam

Chemicals required for visco-elastic foam are little bit different from the chemicals of flexible and rigid foam. The chemicals required for visco-elastic foam are:

Isocyanates

Polyol

Catalyst

Water as blowing agent

Additive

Filler

4.2.1 Isocyanates

Isocyanates are the key components in making good viscoelastic foam [1]. Primary types of isocynates used are MDI (Diphenyl methane di-isocyanate) and TDI (Toluene di-isocyanate) [2]. Viscoelastic foam can be prepared by using blend of polyol with both MDI and TDI alone but the latest advancement in making viscoelastic foam is to use blend of TDI and MDI known as modified MDI. [1]

Basic chemical structures of TDI and MDI are given as :

Figure 4.1 Structures of TDI and MDI [1]

4.2.2 Polyols

Polyols are the major component of visco-elastic foams. The choice of isocyanate is critical when selecting the type of polyol which will give the desired type of foam. [1] Visco- elastic foam can be manufactured by using a standard polyether based polyol with bland of TDI and MDI. Another combination may be the use of MDI with combination of hydrophilic and hydrophobic polyol. [1] Different types of polyether polyols used for VE foam are given in the following table:

Polyol

Molecular Weight

OH #

Viscosity at 25oC

Standard

1000

168

300

Hydrophilic

3600

46

900

Graft

-----

31

3800

Reactive 1

3000

56

550

Reactive 2

3500

25

1200

Table 4.1: Polyether polyols used for the production of visco-elastic foam [1]

Here standard polyether polyol is used as in isocyanate choice blend of TDI and MDI is used. Structure of polyether polyol is :

Figure 4.2 Structure of polyether (graft) Polyol [2]

4.2.3 Catalysts

Tin is mostly used as a catalyst in production of foams. In visco-elastic foam there is a proper impact of gel reaction (reaction of polyol with isocyanate) with tin catalyst. [1] The selection of stannous octoate as a catalyst is necessary for production of visco-elastic foam with standard polyol and isocyanate. [1] While if hydrophilic polyol is used with MDI then no tin catalyst is required. [1] But as we are using blend of TDI and MDI with standard polyether polyol so here stannous octoate will be used as a catalyst.

Chemical formula of stannous octoate is Sn [OCOC7H15]2 [2]

4.2.4 Additives

Additives are required for visco-elastic foam that increases the performance demands of VE foam. Generally diol components like 1,3 butane diol or 1,4 butane diol are used in slabstock plants for the production of visco-elastic foam. [1]

Monols are another unique additive for Visco-elastic foams. Mostly they are used 1 to 3 percent level. Using a monol as an additive in visco-elastic foam will improve the dimensional stability of foam. Benzyl Alcohol ( monol) can be used as an additive in visco-elastic foam. [1]

4.2.5 Fillers

Fillers are valuable option for several reasons. Visco-elastic foams are formulated to achieve high end flammability standards or build density / load. Calcium carbonate can be used as a filler for density load build and residue reduction. [1]

4.3 Experimentation

Experimentation is started by the synthesis of flexible and rigid polyurethane foam in different batches by changing the quantity of chemicals used and also by changing the type of chemicals. After it visco-elastic foam is synthesized in different batches by changing the quantity of chemicals and also by changing the formulation.

4.3.1 Synthesis of Flexible and Rigid polyurethane foam

Flexible and rigid polyurethane foams are produced in different batches with different chemicals and different formulations.

Batch 1:

In first batch flexible foam is synthesized by using crude MDI with polyether polyol. Following steps are followed;

7 grams of crude MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup.

7 gram MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 10 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft flexible foam is formed.

Cream time, gel time and rise time for this batch are 3sec, 5 sec and 10 sec respectively.

Batch 2:

In 2nd batch flexible foam is synthesized by using blend of TDI & MDI with polyether polyol. Following steps are followed;

7 grams of blended MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup.

7 gram of blended MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 12 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft flexible foam is formed.

Cream time, gel time and rise time for this batch are 3sec, 7 sec and 12 sec respectively.

Batch 3:

In 3rd batch rigid foam is synthesized by using crude MDI with blended polyol. Following steps are followed;

5 grams of crude MDI are weighed in a plastic cup using electronic balance.

4.5 grams of blended polyol are taken in a separate cup.

5 gram of crude MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 60 seconds then reaction starts and mixture starts to rise in the cup.

After 5 minutes soft flexible foam is formed.

Cream time, gel time and rise time for this batch are 7sec, 15sec and 1 minute respectively.

Batch 4:

In 4th batch rigid foam is synthesized by using lab grade TDI with polyether polyol. Following steps are followed;

7 grams of TDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 2-3 drops of water are also added in the polyol which will serve as a blowing agent.

7 gram of TDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 7 seconds then reaction starts and mixture starts to rise in the cup.

After 4-5 minutes sticky hard foam is formed.

Cream time, gel time and rise time for this batch are 2sec, 3sec and 7 sec respectively.

Batch 5:

In 5th batch flexible foam is synthesized by using crude MDI with polyether polyol by changing the quantity of chemicals used in batch 1. Following steps are followed;

5 grams of MDI are weighed in a plastic cup using electronic balance.

9 grams of polyether polyol are taken in a separate cup.

5 gram of MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 12 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft flexible foam is formed.

Cream time, gel time and rise time for this batch are 3sec, 6sec and 11 sec respectively.

The experimental data for synthesis of flexible and rigid poly urethane foam is given in the tabulated form as:

Batch No.

Crude MDI

Polyether Polyol

Water

Blend of TDI & MDI

Blended Polyol

Cream Time

Gel Time

Rise Time

1.

7 gram

12 gram

Nil

Nil

Nil

3 s

5s

10 s

2.

Nil

12 gram

Nil

7 gram

Nil

3 s

7 s

12 s

3.

5 gram

Nil

Nil

Nil

4.5 gram

7 s

15 s

1 minute

4.

7 gram lab grade TDI

12 gram

2-3 drops

Nil

Nil

2 s

3 s

7 s

5.

5 gram

9 gram

Nil

Nil

Nil

3 s

6 s

11 s

4.3.2 Synthesis of Visco-elastic polyurethane foam

Synthesis of visco-elastic foam is done in different batches by varying the quantity of chemicals and type of chemicals used in synthesis of Visco-elastic polyurethane foam.

Batch 1:

In 1st batch visco-elastic foam is synthesized by using modified MDI ( blend of TDI & MDI) with polyether polyol. Following steps are followed;

7 grams of modified MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 2-3 drops of water are also added in the polyol which will serve as a blowing agent.

7 gram of modified MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 10 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft visco-elastic foam is formed.

Cream time, gel time and rise time for this batch are 4sec, 6sec and 10 sec respectively.

Batch 2:

In 2nd batch visco-elastic foam is synthesized by using modified MDI ( blend of TDI & MDI) with polyether polyol. Benzyl Alcohol is also added in this batch as an additive. Following steps are followed;

7 grams of modified MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 1-2 drops of benzyl alcohol are also added in the polyol which will serve as an additive.

7 gram of modified MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 15 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft visco-elastic foam is formed with lesser expansion and more softness than batch 1.

Cream time, gel time and rise time for this batch are 5sec, 6sec and 11 sec respectively.

Batch 3:

In 3rd batch visco-elastic foam is synthesized by using modified MDI ( blend of TDI & MDI) with polyether polyol and calcium carbonate ( CaCO3) is added as a filler. Following steps are followed;

7 grams of modified MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 0.1gram of calcium carbonate is also added in the polyol which is used as a filler.

7 gram of modified MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 17 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft visco-elastic foam which is harder than other two batches and rough outer surface is formed.

Cream time, gel time and rise time for this batch are 7sec, 9sec and 17 sec respectively.

Batch 4:

In 4th batch visco-elastic foam is synthesized by using modified MDI ( blend of TDI & MDI) with polyether polyol. Benzyl alcohol is also added as additive and water is also added as blowing agent. Following steps are followed;

7 grams of modified MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 2-3 drops of water are also added in the polyol which will serve as a blowing agent. Also 2-3 drops of benzyl alcohol is added which is an additive.

7 gram of modified MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 10 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft and fine visco-elastic foam is formed.

Cream time, gel time and rise time for this batch are 3sec, 5sec and 10 sec respectively.

Batch 5:

The formulation of 5th batch is same as 4th batch but only catalyst is added. Following steps are followed;

7 grams of modified MDI are weighed in a plastic cup using electronic balance.

12 grams of polyether polyol are taken in a separate cup. 2-3 drops of water are also added in the polyol which will serve as a blowing agent. Also 2-3 drops of benzyl alcohol is added which is an additive.

0.1 gram of stannous octoate (catalyst) is also added in the cup containing polyol.

7 gram of modified MDI is added into the cup containing polyol with gentle stirring.

Stirring is continued for 7 seconds then reaction starts and mixture starts to rise in the cup.

After 2-3 minutes soft visco-elastic foam is formed but less soft than 4th batch.

Cream time, gel time and rise time for this batch are 2sec, 3sec and 7 sec respectively.

The experimental data for synthesis of visco-elastic polyurethane foam is given in the tabulated form as:

Batch No.

Modified MDI (Blend of TDI & MDI)

Polyether Polyol

Water

Additive ( Benzyl Alcohol)

Filler (CaCO3)

Catalyst

(Stannous octoate)

Cream Time

Gel Time

Rise Time

Result

1.

7 gram

12 gram

3-4 drops

Nil

Nil

Nil

4 s

6 s

10 s

Soft VE foam

2.

7 gram

12 gram

Nil

2-3 drops

Nil

Nil

5 s

6 s

11 s

More softer and fine VE foam

3.

7 gram

12 gram

Nil

Nil

0.15 gram

Nil

7 s

9 s

17 s

VE foam with harder outer surface

4.

7 gram

12 gram

2-3 drops

2 drops

Nil

Nil

3 s

5 s

10 s

Soft and very fine VE foam

5.

7 gram

12 gram

2-3 drops

2 drops

Nil

0.1 gram

2 s

3 s

7 s

VE foam with very rapid rise

4.4 Characterization

Characterization is an important step to study the characteristics of the synthesized sample. Characterization of all samples of foam was done by the following techniques:

Calculation of Density

FTIR ( Fourier Transfrom Infrared Spectroscopy)

Thermal Mechanical analysis ( TMA)

4.4.1 Calculation of Density

Density is a structural property and it is defined as mass per unit volume. Different physical properties of foamed polyurethanes are found through apparent density. [3] For simple shaped samples density can be calculated by weighing it and then by finding its volume through linear dimensions but in the case of complex shaped materials especially polyurethane foams and elastomers the method used for calculating density is described in DIN 53479. [3]

In this method the sample is first weighed when it is dry then it is again weighed after dipping it into the test liquid. In this case test liquid taken is water. Density can be calculated by using the formula described in DIN 53479 which is:

QPK = m1. Qv / m2 - m1

Whereas,

QPK = Density of test sample

Qv = Density of test liquid

m1= weight of dry specimen

m2= weight of wet specimen

Density of all samples is calculated by using this standard formula. First we calculate the density of flexible and rigid foam samples then of visco-elastic foam samples.

4.4.1.1 Density of flexible and rigid foam samples

Two samples of flexible foam are taken. First they are weighed when dry and then they are weighed after dipping into the water as water is taken as a test liquid. In case of first sample

m1= 0.306 gram Qv = 1 g/ cm3 m2= 1.235 gram

Density of sample will be 0.329 g/ cm3

In case of second sample of flexible foam :

m1= 0.164 gram Qv = 1 g/ cm3 m2= 1.308 gram

Density of sample will be 0.14 g/ cm3

In case of a sample of rigid foam :

m1= 0.392 gram Qv = 1 g/ cm3 m2= 1.391 gram

Density of sample will be 0.392 g/ cm3

The calculated densities of flexible and rigid foam samples can be represented in bar graph form as:

Figure 4.3 Bar graph representing densities of flexible and rigid foam samples

4.4.1.2 Density of visco-elastic foam samples

There are five samples of visco-elastic foam which are synthesized in lab and one is industrial sample of VE foam. The density of all these samples is calculated by the procedure given above.

Sample 1 (VE foam with full formulation)

For this sample m1= 0.110 gram Qv = 1 g/ cm3 m2= 0.856 gram

Density of sample will be 0.147 g/ cm3

Sample 2 (VE foam with catalyst)

For this sample m1= 0.332 gram Qv = 1 g/ cm3 m2= 2.023 gram

Density of sample will be 0.19 g/ cm3

Sample 3 (VE foam with blowing agent water)

For this sample m1= 0.206 gram Qv = 1 g/ cm3 m2= 1.291 gram

Density of sample will be 0.189 g/ cm3

Sample 4 (VE foam with additive)

For this sample m1= 0.278 gram Qv = 1 g/ cm3 m2= 0.907 gram

Density of sample will be 0.44 g/ cm3

Sample 5 (VE foam with filler)

For this sample m1= 0.268 gram Qv = 1 g/ cm3 m2= 1.229 gram

Density of sample will be 0.278 g/ cm3

Sample 6 (Industrial Sample)

For this sample m1= 0.103 gram Qv = 1 g/ cm3 m2= 1.33 gram

Density of sample will be 0.08 g/ cm3

The calculated densities of visco-elastic foam samples can be represented in bar graph form as:

Figure 4.4 Bar graph representing densities of visco-elastic foam samples

4.4.2 FTIR (Fourier Transform Infrared Spectroscopy)

FTIR is a very important technique in chemistry and it indicates all the functional groups present in a compound in the form of a spectrum and the respective peak value indicates the presence of a respective functional group in that substance. It is a simple technique but used largely due to the versatile result formation. In case of polyurethane foam FTIR is an important because it gives clear path to the structure of foam and indicates all the functional groups present.

FTIR analysis of all the samples of foam was done by using Shimadzu IR Prestige-21/DRS-8000

with a resolution of 4 cm-1 with number of scans 50 and the instrument was run at transmittance mode. The data interval provided by the instrument for a resolution of 4 cm-1 is 1 cm-1. The software used was IR Solution. All spectra were recorded from 4000 to 800 cm-1. Spectra of all foam samples were obtained which indicates the various functional groups present in those samples.

4.4.3 Thermal Mechanical Analysis (TMA)

Thermo mechanical analysis (TMA) determines the dimensional changes in the material as a function of temperature under a defined force. It shows the results in graphical form which describes the changes in the structure of the material on application of force.

In case of polyurethane foam samples the compression set value can be obtained by TMA. TMA of all the samples of foam was carried out by using Q400 thermo mechanical analyzer of TA instruments. In this case all samples are cut to the size of 1 mm and then force is applied in the range of 0.1 to 2 N, while keeping the temperature constant. The change in the structure of foam by the application of force is then studied from the graphs and also the value of compression is obtained from the graph that how much sample gets compressed on the application of certain force.

Chapter 5

Results and Discussions

5.1 Synthesis of flexible and rigid Polyurethane foam

In this phase of experimentation five batches are synthesized in which three are flexible and two are rigid foam. In all the batches the quantity of chemicals is varied to study the effect of that on the final product. And also gel time cream time and rise time for every sample is noted which is different for every batch due to change of formulations.

In first batch the final product is the soft flexible foam and the main ingredients are crude MDI and polyether polyol. Cream time, gel time and rise time for this batch are 3 s, 5s and 10 s respectively. In this batch the final product is flexible foam but not very much softer. In the second batch blend of TDI & MDI is used instead of crude MDI with polyether polyol. In this case flexible foam is achieved but softer than first batch. This softness is due to the use of blend of TDI & MDI as no other chemical is used with polyether polyol so this shows that the blend of TDI & MDI if used increase the softness of the foam. In this batch Cream time, gel time and rise time are 3 s, 7 s and 12 s respectively. Cream time is same as the first batch but there is a slight increase in the gel time and rise time. Now this is the different behavior shown by the mixture and it is clear that it is due to the use of blend of both TDI & MDI. As in first batch only crude MDI is used so there will b less time required to get reaction completed and in the second batch now there are both TDI & MDI now the polyol will react with both of these components so more time will be required that is why there is a difference in the rise time of both batches and rise time of second batch is more than the first batch. But as the reactants rapidly react with each other that's why the time difference is of 1-2 seconds only.

In third batch crude MDI is used with the blended polyol and almost same quantity of both are taken and as a result rigid and hard foam is formed. In this batch hard foam is formed due to the use of blended polyol. In the first batch polyether polyol was used with crude MDI and soft flexible foam was formed but only by changing the type of polyol the type of foam synthesized also gets changed and hard or rigid foam is obtained. Cream time, gel time and rise time are 7 s, 15 s and 1 minute respectively. Now in this batch there is a large difference in cream, gel and rise time as compared to previous batches and rise started after long interval this is due to the change of polyol type and it shows that how by changing the single component in the foaming systems the whole product type gets changed with different properties. In this case rise time reaches to 1 minute because blended polyol is used which have gas mixed in it which causes a large time for polyol to react with isocyanate component so the reaction get completed in more time that's why rise started in 1 minute.

In fourth batch lab grade TDI is used with polyether polyol and new thing here is the use of water as a blowing agent. As a result of this reaction hard and sticky type of foam is obtained. Cream time, gel time and rise time are 2 s, 3 s and 7 s respectively. A s water is used as a blowing agent here so rise time is smaller as compared to the previous batches because water causes the mixture to blow rapidly and as a result reaction gets completed early and mixture stars to rise in the less time. As lab grade TDI is alone used in this batch so the resulting foam becomes hard and rigid and stickiness which was observed on the surface of foam is due to the water un reacted that accumulates over the surface of foam after the reaction completion. This also indicates that the amount of water added is not mixed properly in the mixture that's why it remains unreacted.

In fifth batch crude MDI and polyether polyol are used but their quantity is varied from the previous batches. In this batch crude MDI is taken in lesser quantity and polyol is taken in more quantity and a result more soft, flexible and fine foam is formed. Now this shows that taking the isocyanate component in lesser amount than polyol increases the softness of the foam and if quantity of polyol is taken less than or equivalent to isocyanate component then this will result in the formation of hard and rigid foam. Cream time, gel time and rise time are 3 s, 6 s and 11 s respectively. No major difference is observed in rise time as compared to other batches.

5.2 Synthesis of Visco-elastic polyurethane foam

Five samples of visco-elasatic foam are synthesized with different type of chemicals and by varying the quantities of chemicals used. One industrial sample of visco-elastic foam is also taken to compare the laboratory made visco-elastic foam with it. In first batch the sample is synthesized by using the modified MDI which is actually the blend of TDI & MDI with polyether polyol, also water is used as a blowing agent in small quantity. As a result soft visco-elastic form is obtained. Cream time, gel time and rise time are 4 s, 6 s and 10 s respectively. As water is used as a blowing agent in this batch that's why mixture rises rapidly in a very less time. The final product is soft foam but some viodages are observed in it due to the presence of excess water and it indicates that quantity of water added is greater and it should be lessen to get the finer product.

In second batch the main ingredients are modified MDI and polyether polyol with addition of some additive. Monol ( benzyl alcohol) is used as an additive in this batch. No water is added. As a result soft visco-elastic foam is obtained with more fine surface as compared to the previous batch. This is due to the reason that water is not used here. Cream time, gel time and rise time are 5 s, 6 s and 11 s respectively. In this batch there is a slight difference in the rise time as compared to the first batch and this is due to the reason that no physical blowing agent is used here and mixture starts to rise after the complete reaction of reactants. The addition of additive results in the more finer surface of the foam and it also adds in to the softness of the foam.

In third batch VE foam is synthesized by adding a filler (calcium carbonate) with modified MDI and polyether polyol and as a result the foam obtained is soft foam but with harder outer surface. The roughness of outer surface of the product is due to the calcium carbonate which is used as a filler and also it is found on the surface there is unreacted calcium carbonate present in the pores of foam which shows that the quantity of calcium carbonate added is more and it should be added in lesser quantity to prevent this. Filler actually binds the molecules with each other and help in cross linking but if the quantity of filler is added more than it will result in the incomplete reaction. Cream time, gel time and rise time are 7 s, 9 s and 17 s respectively. Now in this case there is a major difference in gel time and rise time as compared to other batches. This difference is due to the addition of filler as filler is added and also no physical blowing agent is used so mixing is required for more time and the ingredients will react with each other as the mixing continues. There is no rapid rise because the reaction will take time to complete due to the addition of filler and even it is observed that when the mixture take the form of gel then rise will not start at once but rise started after some seconds.

In fourth batch additive is also used with water as a physical blowing agent and rest of reactants are modifeied MDI and polyether polyol. The result of this batch is better than all other batches and very soft visco-elastic foam with very fine surface is obtained. Cream time, gel time and rise time are 3 s, 5 s and 10 s respectively. In this batch rise is rapid due to the use of water as physical blowing agent. The difference here is that additive is used with water and as additive increases the softness of the foam and makes the surface of the foam fine and water also to some extent add into the softness of foam , when these are collectively used the final product and is very fine and very soft foam. That's why the resulting sample of this batch is very much fine and very much soft than other batches and we can say that the result of this batch is a fine and soft visco-elastic foam.

In fifth batch the main reactants are same as previous batches which are modified MDI and polyether polyol, the only addition is of catalyst to see the effect of use of catalyst in foam synthesis. As a result of this reaction soft VE foam is obtained. Cream time, gel time and rise time are 2 s, 3 s and 7 s respectively. In this batch also water and additive are used to make the product more fine and soft. The resulting sample of this batch is almost same as the fourt batch because similar chemicals are used , the only addition is of the catalyst. In this batch a rapid and fast rise is observed and this is due to the catalyst action, as catalyst enhances the rate of reaction without being the part of reaction so due to the addition of catalyst the rise time is very small and reaction gets completed in a very short time and after taking the form of gel mixture at once rise resulting in a fine and soft VE foam. Here the catalyst is used in a very small quantity if it is used in more quantity then the rise will become more less and reaction gets completed in very short time. But in the case of foaming systems catalyst addition should be in a controlled manner because of excess of catalyst can cause the incomplete reaction and mixture can rise without reaction. Here stannous octoate is used as a catalyst.

5.3 Results of Density Calculation

Density of all the synthesized foam samples is calculated by the method described in DIN 53479 standard procedures. In density calculation it is observed that the density of soft foam samples like flexible and visco-elastic foam samples come lower than the density of rigid foam sample. This is due to the softness of the flexible and visco-elasic foam samples and density of rigid foam sample is more due to the hard and rigid surface. Water is used as a test liquid and its density is taken as 1 g/ cm3.

5.3.1 Density results of flexible and rigid foam samples

The density of two flexible foam samples and one rigid foam sample is calculated. The result for rigid foam sample is 0.392 g/ cm3 and the density of two flexible foam samples is 0.329 g/ cm3 and 0.14 g/ cm3. In this calculation the density of one flexible foam sample is almost similar to the density of rigid foam sample and this is due to the reason that the outer surface of the flexible foam sample was hard and rough like rigid foam. There is not any major difference in the density of flexible and rigid foam samples because the first sample of flexible foam have outer surface hard like rigid foam while talking about the other sample of flexible foam whose density came 0.14 g/ cm3, there is a difference between the density values of other foam samples. This difference is due to the reason that the flexible foam sample having low density than other two samples is fine and softer than other two samples. Due to more softness and more finer surface density is lower and the flexible foam sample having density almost same to the density value of rigid foam sample indicates that the flexible foam sample is not soft enough and it have some rigidness and hardness present in it that's why its density value is almost equivalent to rigid foam so in this way density value defines the form of the material.

5.3.2 Density results of Visco-Elastic foam samples

Density of all visco-elastic foam samples is calculated and also the density of industrial sample of VE foam is calculated. The density of all visco-elastic foam samples is same with very slight difference in density values. This slight difference is due to the change of formulations and change in the quantity of chemicals.

The density of industrial sample of visco-elastic foam is found to be 0.08 g/ cm3. Density value of visco-elastic foam sample synthesized by using all the chemicals required for synthesis of VE foam becomes 0.14 g/ cm3. If we compare the density of this foam sample with the calculated density of industrial foam sample then it is clear that there only a slight difference in two density values and we can say from this that the sample of VE foam synthesized is same as industrial sample. Density of VE foam sample in which catalyst is used with other chemicals came to be 0.19 g/ cm3 and for the sample prepared by using water as a blowing agent density is 0.189 g/ cm3. Also in these two samples there is not any difference in value of density.

In case of samples of VE foam with additive and filler the density value is 0.44 g/ cm3 and 0.278 g/ cm3 respectively. Now the density values of these two samples slightly differ from the density of other samples of visco-elastic foam. There may be several reasons for that. In case of additive when additive is used then the density value become higher this may be due to the reason that additive is used and formulation gets changed as compared to other samples. Also there is a possibility that if additive is used with all other chemicals then density will become closer to other VE foam samples but in this case as only additive is used alone so there is a difference. Similar is the situation in case of sample in which filler is used. But if we only talk about these two samples in which additive and filler are used, the density of sample in which additive is used is more than the density of sample in which filler is used. The reason for this is that filler makes soft foam but it led to the hardness of the surface of foam but inner structure of foam is soft due to the filler action and additive also increase the softness of the foam but here density value shows that the foam sample with filler is more soft than the foam sample with additive. By comparing the results of all the samples of visco-elastic foam it can be concluded that all densities are in same range with very slight differences so we can say from density values that we have synthesized different grades of visco-elastic foam.

5.4 Results of FTIR

FTIR of all the samples of flexible, rigid and visco-elastic foam is carried out and spectrum of each sample is obtained in which peaks shows the presence of various functional groups in that sample. The results of all the samples are discussed one by one.

5.4.1 FTIR of Flexible foam sample 1

The spectrum obtained after FTIR of 1st sample of flexible foam shows various peaks at various frequencies indicating the functional groups and type of bonds. Analysis show that the first peak in the spectra at the frequency of 3342.64 cm -1 is due to the presence of alkynes and showing the specific bond type of C-H stretch and the very next peak at 2976.16 cm -1 is due to alkanes C-H but with specific bond C=CH2. The next peak at 2872 cm -1 is showing the presence of specific methyl bond in C-H and this also indicates the presence of MDI due to specific methyl bond. Next peak at 1703.14 cm -1 indicates the presence of carboxylic acid derivatives C=O and this relates to the structure of polyol used as a main ingredient in foam synthesis. The next peak in spectra attributes to the presence of dienes and it is at 1598.99 cm -1, then the peak at 1537.27 cm -1 indicates the presence of aliphatic nitro compounds N-O and this may be due to isocyanates. The next two peaks at 1514.12 cm -1 and 1448.54 cm -1 indicates the presence of aromatic rings with bonds C=C, and this is due to the structure of MDI & TDI. The next peak at 1409.96 cm -1 shows C-H bend while the next two peaks at 1371.39 and 1307.74 cm -1 show alkanes with specific bond of C-C stretch. Next peak in the spectrum at 1228.66 cm -1 attributes to the presence of amines with specific bond of C-N. The peak at 1097.50 cm -1 indicate alkanes with C-C stretch and last three peaks at 1016.49, 925.83 and 819.75 cm -1 shows C-H bend.

5.4.2 FTIR of Flexible foam sample 2

FTIR spectra of second sample of flexible foam is almost same as that of first sample and it almost shows the same peaks at same frequencies as in the spectra of sample 1 which indicates that all the same functional groups are present in the second sample as that of first sample and it is due to the reason that almost same chemicals are used for the synthesis of these samples that's why the respective spectra of both the samples is same showing that all the same groups with same bonds are present in second sample which are described in the analysis of first sample.

5.4.3 FTIR of Flexible foam sample 3

FTIR spectra of third sample of flexible foam show some different peaks and different frequencies as compared to the spectra of first two samples. This indicates the presence of some additional functional groups and bonds not present in the first two samples and this is due to the slight change in chemicals used in the synthesis of this sample. In spectrum of this sample first peak is at 3782.41 cm-1 which shows the presence of water contaminant and indicates that there is some un reacted water present in the sample. Now this indicates the use of water in synthesis of this sample of flexible foam while this peak was not present in the spectra of first two samples because in those samples water is not used. Second peak at 3327.21 cm-1 indicates the presence of O-H group which can be alcohols or phenols. Next peak at 2877.79 cm-1 accounts for the presence of alkanes with C-H stretch and it was also present in the first two samples. Peak at 1712.79 cm-1 shows C=O saturated carboxylic acid derivatives same as appeared in the spectra of previous samples. At 1597.06 cm-1 there is a peak showing aromatic ring with specific bond of C=C and it is due to the structure of MDI. The next two peaks at 1523.76 and 1419.61 cm-1 shows aromatic nitro compounds with specific bond N-O and this is due to the reason that in the structure of MDI or TDI cyanate group is attached to aromatic ring. Peak at 1301.95 and 1224.80 cm-1 indicates C-O ethers due to the presence of polyether polyol. Peak at 1093.64 cm-1 indicates C-C stretch and rest of three peaks show C-H bend till the last peak at 696.30 cm-1 which also shows C-H bend in aromatic rings.

5.4.4 FTIR of Rigid foam sample 1

FTIR spectra of rigid foam sample show peaks almost same as the spectra of flexible foam samples and it is due to the reason that the main ingredients of foam are same which are isocyanates and polyols only their quantity makes the foam flexible or rigid. But there are some differences also in the peaks as compared to the spectra of flexible foam samples. In spectra of first sample of rigid foam there is a peak at 3782.41 cm-1 showing water contaminant and presence of water in the sample. Peak at 3346.50 cm-1 indicates C-H stretch of alkynes and peak at 2877.79 cm-1 indicates C-H stretch of aliphatic alkanes. Peaks at 1597.06 and 1452.40 cm-1 show the presence of aromatic rings which are due to isocyanate structure. Peak at 1242.16 cm-1 show aromatic ethers which are due to polyether polyol. Peaks at 1097.50 and 923.90 cm-1 show C-C stretch and C-H. Peaks at 840 and 690.52 cm-1 show C-H bend of aromatics.

5.4.5 FTIR of Rigid foam sample 2

In spectra of second sample of rigid foam there is no peak showing water as in the spectra of first sample of rigid foam this is due to the reason that no water is used in the synthesis of this sample of rigid foam. The first peak at 3338.78 cm-1 shows the C-H stretch of alkynes and peak at 2976.16 cm-1 indicates alkanes having specific bond of C=CH2. The peak at frequency 2872.01 cm-1 shows C-H with specific methyl bond which indicates the presence of MDI. At frequency 1703.14 cm-1 peak attributes to the presence of C=O carboxylic acid derivatives which are due to the structure of polyol. Peak at 1598.99 cm-1 shows C-C dienes and at 1512.19 cm-1 peak shows the presence of aromatic nitro compounds C-N. Peaks at 1450.47 and 1408.04 cm-1 shows aromatic rings which are due to isocyanate structures. At 1373.32 cm-1 peak attributes to the presence of aliphatic nitro compounds N-O. Peak at 1230.58 cm-1 shows alcohols or phenols. Peak at 1097.50 cm-1 indicates C-C stretch of alkanes and peaks at 925.83, 819.75, 759.95 and 698.23 cm-1 are showing C-H bend of alkenes.

5.4.6 FTIR of Visco-Elastic foam (Industrial sample)

FTIR of VE foam show one or two different peaks as compared to the spectra of flexible and rigid foam samples. The first peak at 3782.41 cm-1 shows water contaminant and indicates that water is used in the synthesis of this sample and some of the water remain un reacted or the quantity of water added was more and water added was not utilized in the reaction completely. This peak is also in spectra of some of samples of flexible and rigid foam in which water is used in synthesis. Peak at 3290.56 cm-1 indicates the C-H stretch of acetylenic alkynes and peak at 2974.23 cm-1 indicates aliphatic alkanes C-H with specific bond of C=CH2. The peak at frequency 1712.79 cm-1 indicates the presence of saturated carboxylic acid derivatives C=O. At 1597.06 cm-1 peak shows the presence of aromatic rings and at 1469.76 cm-1 peak shows C-H bend with methylene specific bond that indicates the presence of MDI. Peak at 1539.82 cm-1 shows amines C-N which is due to presence of cyano group in isocyanate structure. At 1220.94 cm-1 aromatic ethers are present which indicates the presence of polyether polyol in sample. At 1097.50 cm-1 peak shows C-C stretch of alkanes and then C-H bend of alkanes at 918.12 cm-1. The peaks at 758.02 and 686.66 cm-1 show aromatic rings.

5.4.7 FTIR of Visco-Elastic foam (Sample with full formulation)

FTIR spectra of VE foam sample which is synthesized with full formulation is similar to the spectra of industrial VE foam sample which shows that visco-elastic foam synthesized by us is same as the industrial sample of visco-elastic foam. So we can say by comparing the FTIR results of both the samples that we have synthesized visco-elastic foam.

In spectra of this sample the first peak comes at 3782.41 cm-1 which shows water contaminant and it is also present in the spectra of industrial sample. The peak at 3329.14 cm-1 shows the C-H stretch of alkynes and peak at 2879.72 cm-1 show C-H stretch of aliphatic alkanes. These three peaks are same as appeared in the spectra of industrial sample showing same groups and bonds. At 1710.86 cm-1 peak indicates saturated carboxylic acid derivatives with bond C=O same as appeared in the spectra of industrial sample of VE foam. Peak at 1597.06 cm-1 shows aromatic rings and peak at 1525.69 cm-1 indicates the presence of nitro compounds N-O. Peak at 1361.74 cm-1 shows the presence of C-N amines and peaks at 1301 and 1288.66 cm-1 indicates the presence of aromatic ethers C-O which is due to polyether polyol and same as appeared in the spectra of industrial sample. At 1095.57 cm-1 there is C-C stretch of alkanes and at 923.90 cm-1 peak shows C-H bend of alkenes. At 827.46 cm-1 and 758.02 cm-1 peak shows C-H bend of aromatic rings. Based on this analysis we can say that VE foam sample synthesized in lab is same as that of industrial VE foam sample because FTIR spectra of both are same with slight difference in the values of frequency showing same functional groups in both samples.

5.4.8 FTIR of Visco-Elastic foam (Sample with Catalyst)

FTIR spectra of VE foam sample in which catalyst is used is same as that of other samples of VE foam and no major difference is observed. The difference is it does not show any peak indicating water contaminant which shows that water is not used in synthesis of this sample. Peak at 3329.14 cm-1 shows C-H stretch of alkynes and peak at 2872.01 indicates C-H with specific bond methyl which shows the presence of MDI. Rest of the peaks in the spectra are same as the spectra of previous samples and show same functional groups and same frequency values indicating that the same chemicals are used in synthesis as of previous sample and use of catalyst do no effect the results of FTIR.

5.4.9 FTIR of Visco-Elastic foam (Sample with blowing agent)

FTIR spectra of VE foam synthesized using a blowing agent is also same as spectra of previous samples showing that same chemicals are used. There is only a slight difference of the frequencies but the functional groups at those frequencies are same as previous samples of VE foam. First three peaks shows the same C-H stretch and C-H with specific bonds. At 2870.08 cm-1 the peak shows C-H alkyl bond with methyl as a specific bond which is due to the presence of MDI. Peak at 1703.14 cm-1 shows carboxylic acid derivatives and other rest peaks show aromatic rings, aliphatic nitro compounds, ethers and in the end of spectrum all peaks show C-H bend of alkenes.

5.4.10 FTIR of Visco-Elastic foam (Sample with additive)

FTIR spectra of VE foam with additive is same as previous sample and no change is observed showing that addition of additive have no effect on FTIR results. All peaks in the spectra of this sample show same functional groups as in the previous samples. Additive used here is monol ( benzyl alcohol) and at 1307.74 cm-1 peak shows the presence of C-O alcohols that justify the presence of benzyl alcohol in the sample that is used as an additive, rest of peaks are same.

5.4.11 FTIR of Visco-Elastic foam (Sample with filler)

FTIR of VE foam exhibit the same results as of previous sample. As CaCO3 is used as a filler in this sample it have no effect on the FTIR spectra because spectrum of this sample is same as of previous samples of VE foam. There is a little difference in the values at which peak occurs but the functional groups of all the peaks are same as in the spectra of previous samples. In start the peaks show C-H stretch and bend with some specific bonds like methyl bond shown at 2868.15 cm-1. Then there are different functional groups like carboxylic acid derivatives, aromatic and aliphatic nitro compounds, aromatic rings etc. All the functional groups are same as in the spectra of previous samples of VE foam.

5.5 Results of Thermal Mechanical Analysis (TMA)

Thermal Mechanical Analysis of samples of flexible, rigid and visco-elastic foam was carried out and results are obtained in the form of graphs and these are discussed one by one.

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