Optimizing the Properties of Polyether Based Polyurethane Foam

doi:10.4236/ojpchem.2013.34015

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Open Journal of Polymer Chemistry, 2013, 3, 86-91

Published Online November 2013 (http://www.scirp.org/journal/ojpchem)

http://dx.doi.org/10.4236/ojpchem.2013.34015

Open Access OJPChem

Optimizing the Properties of Polyether Based

Polyurethane Foam

F. O. Aramide1*, P. O. Atanda2, E. O. Olorunniwo2

1Metallurgical and Materials Engineering Department, Federal University of Technology, Akure, Nigeria

2Materials Science and Engineering Department, Obafemi Awolowo University, Ile-Ife, Nigeria

Email: [email protected], *[email protected], atanda[email protected], [email protected]

Received July 4, 2013; revised August 25, 2013; accepted September 3, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Effect of different chemicals and additives used in producing polyester foam was investigated. Reference samples were

produced from polyol, toluene di isocyanate (TDI), amine stannous octoate distil water, and silicone oil using laboratory

mix formulation based on 500 g polyether based polyol. Other samples were produced by consecutively varying the

content of all the additives with the exception of polyol. Standard sample dimensions for density test, indentation test,

compression set test, tensile strength and elongation tests were produced from the samples. The various tests were car-

ried out on the samples using the ASTM-D3574 standards. It was observed that the degree of indentation affects the

value of indentation hardness and increasing the percentage content of TDI results in acceptable compression set value

for the polyester samples. It was concluded that Holding all other parameters constant, reducing the water content and

increasing the TDI content will yield polyester foam of optimum properties.

Keywords: Hardness; Polyester Foam; Compression Set and Optimum Properties

1. Introduction

Polyester are generally referred to as stable polymers and

they are reaction products of etherification of di- or poly-

hydric alcohol with di- or poly-basic acids and anhydri-

des. They are broadly categorized into saturated and un-

saturated polyesters [1]. Unsaturated polyesters are

widely used in the composite industry. They can provide

excellent mechanical and chemical properties, good che-

mical and weather resistance, and a low cost. Further

advantages of unsaturated polyester resins over other

thermosetting resins for they are easy to handle, can be

pigmented, and can be easily filled and fibre reinforced

in a liquid form [2]. These are normally produced in

three steps; the polycondensation reaction of di-alcohol,

an acid anhydride and a di-acid into a pre-polymer resin.

This is followed by the addition of monomer and lastly,

curing of the polyester resin into a thermoset polymer by

an organic peroxide [3].

Polyester materials are used as chemical resistant fin-

ishes for interiors of chemical and petrochemical storage

tanks [4]. They are also utilized as biomaterials as syn-

thetic vascular grafts being intensively used in vascular

system surgery [5], among others they are used as by-

passes to derive blood circulation or to replace failed

blood vessels [6-10]. Many researchers have done won-

derful work on polyester material [11-14] but very little

has actually focused on optimizing the property of po-

lyester foam by investigating the influence of additives

on the properties of the resulting polyester foam. This

research endeavours to focus in this direction.

2. Materials and Methods

The materials for this work are; polyol, toluene-diisocy-

anate (TDI), amine, distil water, silicone oil, stannous

octoate, moulding box lined with thin plastic sheet, elec-

trically operated stirrer, electronic balance and stop

watch.

2.1. Sample Preparation

Polyol and toluene-diisocyanate (TDI) were weighed into

separate containers. This was followed by weighing distil

water, silicone oil and amine sequentially into a container,

mixed thoroughly and then poured into the earlier meas-

ured polyol. This was mixed thoroughly for 30 seconds

followed by the addition of stannous octoate while mix-

*Corresponding author.

F. O. ARAMIDE ET AL. 87

ing for the about 10 seconds. Finally the measured TDI

was added, rapidly mixed for 5 seconds and then care-

fully and quickly poured into the prepared mould box.

From this point, the stop watch was used to monitor and

record the rising time. On attainment of foam full rise,

the solidified foam was removed from the mould box for

further experimentation.

2.2. Mathematical Formulation of Reference

Sample

For the purpose of this work, a reference sample of den-

sity 23 Kgm−3 was selected. In order to achieve this ref-

erence sample’s density, the weights of various additives

to be added were calculated using laboratory mix formu-

lation, fixing the mass of polyol at 500 g [11-13]. The

formulation for the reference sample is show in Table 1.

Other various samples used for this research work

were produced by varying the mass of an additives used

at time with the exception of polyol by ±20% of the

weight used for the additive, while the other remain con-

stant. Through this all other samples were separately

produced.

2.3. Sample Machining

From each of the different samples produced, regular

shaped foam blocks were produced to make them suit-

able for machining. The machining of the samples pro-

duced standard test sample’s dimensions for investigat-

ing the mechanical properties of the samples.

2.4. Investigation of Various Properties

Three test samples were used to measure each property

and the average value was calculated and recorded. Each

of the tests was carried out as outlined in the ASTM-

D3574 [13-16].

2.4.1. Density

Flat surface cuboids (test pieces) were cut out from each

of the samples of foam produced. The dimensions of

each test piece is measured in meters, from these the

volume was calculated. Then the mass of the test piece

was measured, using the electronic weighing balance, the

Table 1. Formulation for the reference sample.

Additive Actual mass (g)

Polyol 500

TDI 262

Distil water 21

Silicone oil 5

Stannous octoate 0.9

Amine 0.9

value of this was recorded in kilograms. From the data

generated the density of each test piece was calculated

and recorded.

2.4.2. Indentation Hardness Index Test

The indentation hardness index (IHI) of foam is a meas-

urement of its load bearing ability. This is the force re-

quired to depress a small circular plate into the foam.

The test sample is placed on the support plate and ad-

justed so to locate the centre of the sample below the

centre of the indenter. The operation of the indentation

machine was initially set to 65% of the sample’s thick-

ness and the a force of 5 N (Newton) was applied to the

test area; on getting to the 65% of the sample’s thickness,

the process stopped and sample was allowed to rise up

under the indenter for 60 seconds then the hardness value

was read off the calibrated scale on the machine. The

machine was then set to 60% of the sample’s thickness

and the process was repeated but this time the sample

was allowed to rise under the indenter for 45 seconds and

hardness value was measured and recorded.

2.4.3. Compression Set Test

The test sample of dimensions 50 mm × 50 mm × 25 mm

was cut out. The initial thickness of the sample was

measured and recorded. The sample was placed between

the horizontal plates of a compression device; each of the

horizontal plates has a greater surface area than the test

sample. The compression plates were so arranged while

holding the sample to be parallel to each other, and the

space between them was adjusted to the required de-

flected height.

The sample was compressed to 75% of its original

thickness, maintained at this known condition for 72

hours. The sample was removed, allowed to recover for

30 minutes and the final thickness was measured and

recorded. The compression set is calculated from:



oro

Compression set100TTT

where: To is the original thickness of sample

Tr is the thickness of sample after recovery

2.4.4. Tensile Strength

This test gives information on the elasticity of the foam,

it also indicates the strength of foam sample under ten-

sion.

The tensile tests were performed on various samples

using Monsanto tensometer. The fracture load for each

sample was noted as well as the diameter at the point of

fracture and the final gauge length. The initial diameter

and initial gauge length for each sample was noted before

uniaxial load. From the generated data the ultimate ten-

sile strength and percentage elongation of each sample

was calculated.

F. O. ARAMIDE ET AL.

3. Results and Discussions

Tables 2-5 show the effects of varying additive content

on the density of the polyester sample; the effects of

varying additive content on the tensile property of the

polyester sample; the effects of varying additive content

on the indentation hardness index of the polyester sample

and the effects of varying additive content on the com-

pression set of the polyester sample respectively. Fur-

thermore, Figures 1-5 show the effect of varying addi-

tives on the density of the polyester sample; the effect of

varying additives on the tensile strength of the polyester

sample; the effect of varying additives on the percentage

elongation of the polyester sample; the effect of varying

additives on the hardness of the polyester sample and the

effect of varying additives on the compression set value

of the polyester sample.

Table 2. Effects of varying additive content on the density of

the polyester sample.

Varying

Additive Mass (Kg) Volume (m3) Density

(Kgm−3)

−20% TDI 0.161 0.00705 22.8

−10% TDI 0.164 0.00710 22.94

+10% TDI 0.162 0.00719 22.53

+20% TDI 0.153 0.00728 21.02

−20% Distil Water 0.144 0.00811 17.75

−10% Distil Water 0.152 0.00802 18.95

+10% Distil Water 0.158 0.00814 19.41

+20% Distil Water 0.165 0.0831 19.85

−20% Amine 0.156 0.00679 22.9

−10% Amine 0.153 0.00661 23.11

+10% Amine 0.165 0.00689 23.94

+20% Amine 0.168 0.00709 23.6

−20% Stannous

Octoate 0.174 0.00688 25.3

−10% Stannous

Octoate 0.168 0.00679 24.74

+10% Stannous

Octoate 0.159 0.00683 23.27

+20% Stannous

Octoate 0.163 0.00695 23.5

−20%

Silicone oil 0.167 0.00742 22.5

−10%

Silicone oil 0.161 0.00708 22.74

+10%

Silicone oil 0.156 0.00674 23.15

+20%

Silicone oil 0.161 0.00709 22.7

Reference Sample 0.218 0.00939 23.2

Table 3. Effects of varying additive content on the tensile

property of the polyester sample.

Varying Additive Elongation (%) Tensile Strength

(Nmm−2)

−20% TDI 157.5 110.2

−10% TDI 145.4 102.4

+10% TDI 45.8 102.4

+20% TDI 50.3 102.4

−20% Distil Water 35.9 102.4

−10% Distil Water 33.6 102.4

+10% Distil Water 111.7 78.7

+20% Distil Water 95.8 86.6

−20% Amine 115.9 181.1

−10% Amine 117.6 173.2

+10% Amine 110.3 133.8

+20% Amine 95.5 125.9

−20% Stannous Octoate 86.5 149.6

−10% Stannous Octoate 85.3 149.6

+10% Stannous Octoate 82.8 133.8

+20% Stannous Octoate 86.0 141.7

−20% Silicone oil 77 118.1

−10% Silicone oil 71.5 118.1

+10% Silicone oil 87.6 125.9

+20% Silicone oil 81.2 118.1

Reference Sample 129.7 165.4

-30 -20 -100102030

V arying Ad d itves (%)

Den sity (Kgm

-3

)

TDI Water Amine

S.O. Silicone

Figure 1. Effect of varying additives on the density of the

polyester sample.

From Figure 1 and Table 2 the effect of varying the

various components on the density of the polyester sam-

ple is clearly seen. It is seen that the density of the refer-

ence sample is 23.2 Kgm−3; reducing/increasing the per-

centage content of toluene-diisocyanate (TDI) results in

the reduction of the density of the resulting sample, the

same thing is applicable when the percentage of distil

water used is varied. In the case of percentage amine

used in the production of the polyester sample, reducing

Open Access OJPChem

F. O. ARAMIDE ET AL. 89

Table 4. Effects of varying additive content on the inden-

tation hardness index of the polyester sample.

Varying Additive

Indentation

to 65%

Thickness

Hardness

Value

Indentation

to 60%

Thickness

Hardness

Value

−20% TDI 31.28 97 28.87 100

−10% TDI 30.07 76 27.76 89

+10% TDI 30.10 163 27.79 197

+20% TDI 31.32 198 28.91 214

−20% Distil Water 37.26 193 34.39 219

−10% Distil Water 32.41 159 29.92 203

+10% Distil Water 30.65 84 28.29 112

+20% Distil Water 31.73 93 29.29 106

−20% Amine 31.21 126 28.81 137

−10% Amine 30.64 121 28.28 121

+10% Amine 32.03 127 29.57 127

+20% Amine 32.14 131 29.67 145

−20% Stannous

Octoate 28.73 139 26.52 152

−10% Stannous

Octoate 29 131 26.77 138

+10% Stannous

Octoate 29.45 128 27.19 136

+20% Stannous

Octoate 28.93 134 26.7 147

−20% Silicone oil 29.05 124 26.81 134

−10% Silicone oil 28.73 122 26.52 119

+10% Silicone oil 29.88 123 27.58 115

+20% Silicone oil 30.81 121 28.44 133

Reference Sample 41.03 151 37.87 167

114

134

154

174

-40 -2002040

Varying Additive s (%)

Tensile Strength

(Nmm

-2

)

TDI Water Amine

S.O. Silicone

Figure 2. Effect of varying additives on the tensile strength

of the polyester sample.

the content of amine results in reduction of the density of

the polyester, while increasing the content of amine re-

sults in increased density of the polyester samples. More-

over, reducing the percentage content of stannous octoate

in the polyester content results in increase density also

increasing the content of stannous octoate results in

slight increase in the density of resulting sample [17].

For silicone oil, reducing/increasing the percentage con-

tent of silicone results in the reduction of the density of

the resulting sample.

Furthermore, from Table 3, Figures 2 and 3, the effect

of varying the components of the polyester samples on

their tensile properties is elucidated. It is seen that the

tensile strength of the reference sample is 165.4 Nmm−2;

reducing/increasing the percentage content of toluene-

diisocyanate (TDI) results in the reduction of the tensile

strength of the resulting sample, the same trend is ob-

served when the percentage of distil water used is varied.

In the case of percentage amine used in the production of

the polyester sample, reducing the content of amine re-

sults in an increment in the tensile strength of the poly-

ester, while increasing the content of amine results in

reduction in tensile strength of the polyester samples.

Moreover, similar to what was observed in TDI, reduc-

ing/increasing the percentage content of stannous octoate

in the polyester content results in reduction in the tensile

strength of resulting samples. For silicone oil, reducing/

increasing the percentage content of silicone results in

the reduction of the tensile strength of the resulting sam-

ples. From Figure 3, the percentage elongation of the

reference sample is 129.7, reducing the percentage con-

tent of TDI in the polyester samples results in an incre-

ment in the elongation of the sample while increasing the

TDI content in the samples results in a reduction in the

elongation to failure of the resulting polyester samples.

For the other additives, the maximum elongation is ob-

served in the reference sample; that is reducing or in-

creasing the percentage content of the other additive re-

sults in reduction in the elongation (ductility) of the re-

sulting polyester samples.

Moreover, Table 4 and Figure 4 show clearly the ef-

fect of varying the content of the various additives of the

indentation hardness values of the various resulting sam-

ples. The values of the indentation hardness samples in-

dented to 65% and 60% of the samples’ thickness were

110

130

150

-30-20 -100102030

Va rying Additives (%)

El ongation (%)

TDI WaterAmine

S.O. Silicone

Figure 3. Effect of varying additives on the percentage

elongation of the polyester sample.

F. O. ARAMIDE ET AL.

Table 5. Effects of varying additive content on the compres-

sion set of the polyester sample.

Varying

Additive

Initial

Thickness

(cm)

Final

Thickness

(cm)

Compression

Set Value (%)

−20% TDI 2.51 1.35 46.2

−10% TDI 2.51 1.62 35.5

+10% TDI 2.51 2.28 9.2

+20% TDI 2.51 2.21 11.9

−20% Distil Water 2.51 2.25 10.4

−10% Distil Water 2.51 2.26 9.9

+10% Distil Water 2.51 1.97 21.5

+20% Distil Water 2.51 2.04 18.7

−20% Amine 2.51 2.31 7.9

−10% Amine 2.51 2.29 8.8

+10% Amine 2.51 2.25 10.4

+20% Amine 2.51 2.22 11.6

−20% Stannous

Octoate 2.51 2.15 14.3

−10% Stannous

Octoate 2.51 2.07 17.5

+10% Stannous

Octoate 2.51 2.04 18.7

+20% Stannous

Octoate 2.51 2.05 18.3

−20% Silicone oil 2.51 2.28 9.2

−10% Silicone oil 2.51 2.27 9.6

+10% Silicone oil 2.51 2.16 13.9

+20% Silicone oil 2.51 2.19 12.7

Reference Sample 2.51 2.23 11.2

110

130

150

170

190

210

-30 -20 -100102030

Varying Additive s (%)

Hardness Value

TDI (65%)TDI (60%)W a t e r (65%)

Wate r (60%)A m ine (65%)A m i ne (60% )

S . O . (65% )S.O. (60%)Sil. (65%)

Sil. (60%)

Figure 4. Effect of varying additives on the hardness of the

polyester sample.

-30 -20 -100102030

Varying Additive s (%)

Com pr essi on Set V al ue (% )

TDI Water Amine

S.O.Silicone

Figure 5. Effect of varying additives on the compression set

value of the polyester sample.

plotted against the percentage composition of the various

additives. It is observed that when the samples were in-

dented to 65% of the thickness, the reference sample has

the indentation hardness of 151 and when the samples

were indented to 60% of the samples’ thickness the ref-

erence sample has the indentation hardness of 167. For

both cases, reducing the TDI content in the samples re-

duces the hardness values of the polyester samples while

increasing the TDI content of the samples increases the

hardness values of the polyester samples. Conversely,

reducing the water content increases the hardness values

of the samples, while increasing the water content re-

duces the hardness values of the polyester samples. For

other additives, the highest value of indentation hardness

in both cases is observed in the reference sample; reduc-

ing/increasing the percentage content of other additives

results in reduction of the indentation hardness values.

From Table 5 and Figure 5, the compression set value

of the reference sample is 11.2, reducing the TDI content

in the polyester sharply increases the compression set

values of the polyester samples increasing the TDI con-

tent in the samples slightly reduces the compression set

value and then begins to increase slightly. In the case of

distil water, amine and silicone oil, the compression set

values of the samples reduced with reduction in the con-

tent of the respective additive and increased with in-

crease of the same. The shape of the graph relating the

relationship between the compression set of the sample

and percentage content of stannous octoate is sinusoidal.

With the exception of TDI, the range of compression set

values resulting from varying the percentage content of

the additives falls within acceptable range [17]. The com-

pression set value obtained by reducing the percentage

content of TDI was outside the acceptable range but as

Open Access OJPChem

F. O. ARAMIDE ET AL.

the TDI content is increased, it falls within the acceptable

range.

4. Conclusion

From the observations discussed it can be concluded that:

 With the exception of amine and stannous octoate, all

the other additives have values at which the density is

optimum, and these values produced the optimum

density of 23.2 Kgm−3. The density of the foam sam-

ples increases with decrease or increase in the per-

centage content of stannous octoate used. The density

of the polyester samples also increases with increased

percentage content of amine.

 With the exception of amine, the tensile strength of

the polyester samples decreases with decrease/in-

crease in the percentage content of all the other addi-

tives. The optimum tensile strength coincides with

that of the reference sample for various percentage

contents of all other additives. The tensile strength of

the samples reduces with increase in percentage con-

tent of amine.

 With the exception of TDI, the elongation of the

polyester samples decreases with decrease/increase in

the percentage content of all the other additives. The

optimum tensile strength coincides with that of the

reference sample for various percentage contents of

all other additives. The elongation of the samples re-

duces with increase in percentage content of TDI.

 With the exception of TDI and distil water, the in-

dentation hardness of the polyester samples decreases

with decrease/increase in the percentage content of all

the other additives. The optimum indentation hard-

ness coincides with that of the reference sample for

various percentage contents of all other additives. The

indentation hardness of the samples reduces with in-

crease in percentage content of distil water and in-

creases with increase in TDI.

 The degree of indentation affects the value of inden-

tation hardness; the higher the degree of indentation,

the higher the indentation hardness value.

 Increasing the percentage content of TDI results in

acceptable compression set value for the polyester

samples.

 Holding all other parameters constant, reducing the

water content and increasing the TDI content will

yield polyester foam of optimum properties.

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