Polymer Properties (EBT 326) Exp. 4: FTIR

EXPERIMENT 4

Determination of Functionality in Polymeric Materials

1.0 OBJECTIVE

1.1 To investigate the functional groups of polymeric materials and polymer blends.

1.2 To find out how FTIR spectroscopy differentiate types of blends.

2.0 INTRODUCTION

An infrared spectrum represents a fingerprint of a sample with absorption peaks which

correspond to the frequencies of vibrations between the bonds of the atoms making up the

material. Because each different material is a unique combination of atoms, no two

compounds produce the exact same infrared spectrum. Therefore, infrared spectroscopy can

result a positive identification (qualitative analysis) of every different kind of material. In

addition, the size of peaks in the spectrum is a direct indication of the amount of material

present. With modern software algorithms, infrared is an excellent tool for quantitative

analysis. [1]

On the other hand, there are two types of IR spectroscopies, dispersive spectroscopy

and fourier transform infrared spectroscopy (FTIR spectroscopy). The major difficulty from

using dispersive spectroscopy is slow scanning process, hence FTIR spectroscopy was

developed to overcome dispersive spectroscopy weakness. The difference between both of

them is the placement of interferometer. The interferometer cut the rambling process of

dispersive spectroscopy and produces a unique type of signal which has all of the infrared

frequencies encoded into it. This convenient makes the signal can be measured quicker than

dispersive spectroscopy [2]. Thus the time process is cut out in FTIR spectroscopy. The

interferogram is then converted by the fourier transform software into a spectrum of

transmittance against wave number [3]. Most importantly, FTIR spectroscopy has a single

beam, whereas dispersive spectroscopy usually has a double beam. Assuming there is no

change in atmospheric conditions throughout the experiment, this does not cause a problem.

Page | 1

Polymer Properties (EBT 326) Exp. 4: FTIR

However, for highly sensitive work and experiments which take a long time, changes in

infrared absorbing gas concentration can severely affect the results. Therefore, in these cases,

when using an FTIR spectroscopy, it is necessary to purge the instrument of CO2 and water

vapour using an infrared transparent gas such as nitrogen.

There are also some advantages while using FTIR spectroscopy compared to

dispersive spectroscopy [1]:

It is a non-destructive technique

Provide the spectrum much more rapidly than the dispersive spectrometer.

It provides a precise measurement method which requires no external calibration,

more accurate in accuracy and improved in resolution

Have ability to work over a greater range of infrared intensities

It can increase speed, collecting a scan every second

It can increase sensitivity – one second scans can be co-added together to ratio out

random noise

It has greater optical throughout

It is mechanically simple with only one moving part

There are several types of sample preparation, for solid specimen we could use attenuated

total refection (ATR). If the sample is in powder form we could use KBr as a fastener for our

powder sample and pressing the mixture under high pressure. Nujol Mull also can be used for

sample in powder form, it involves grinding the compound with mineral oil (Nujol) to create

a suspension of the finely ground sample dispersed in the mineral oil.

Page | 2

Polymer Properties (EBT 326) Exp. 4: FTIR

Figure 1: FTIR spectroscopy sample analysis process

Figure 2: FTIR spectroscopy layout

Page | 3

Polymer Properties (EBT 326) Exp. 4: FTIR

3.0 MATERIALS AND EQUIPMENT

3.1 Materials of polymer and polymer blends

3.1.1 Pure/Virgin Polypropylene (PP)

3.1.2 Alumina (Al2O3)

3.1.3 7 wt% PP/Al2O3 Composite

Figure 3: Al2o3 composite, alumina powder, PP

3.2 Fourier transform infrared spectroscopy (FTIR spectroscopy)

Figure 4: FTIR spectoscopy machine

Page | 4

Polymer Properties (EBT 326) Exp. 4: FTIR

3.3 Tweezer

Figure 5: tweezer

3.4 Attenuated Total Reflectance (ATR) sample holder

Figure 6: ATR for solid and powder sample

Page | 5

Polymer Properties (EBT 326) Exp. 4: FTIR

4.0 PROCEDURE

4.1 Raw materials without other preparation were prepared.

4.2 Sample holder (ATR) was cleaned and then attached to the FTIR machine (Spectrum

RX)

4.3 ‘Spectrum V5.3.1’ software was launched on the desktop.

4.4 For calibrate sample holder, ‘Instrument’ button was selected, then ‘scan background’

and ‘review’, ‘overwrite’ and lastly ‘delete background scan’.

4.5 Using a tweezers, solid sample was placed on the sample holder and the sample has to

nicely cover the sample holder surface.

4.6 The solid sample was indented and locked by the anvil of sample holder.

Figure 7: The sample was locked by the anvil

4.7 ‘Instrument’ button is clicked, then for scanning the sample, ‘scan sample’ was

selected, at ‘scan parameter ATR end’ was setting to 650cm-1 and ‘ok’. The sample

was scanned by selected ‘scan sample’. When the ‘scan complete’ dialog box

appeared, the scan was finally completed.

4.8 The spectrums were collected and saved to avoid data loss.

Page | 6

Polymer Properties (EBT 326) Exp. 4: FTIR

4.9 For analysis, ‘process’ was selected from menu, as for broaden the peaks, ‘smooth’

was clicked and the ‘view’ for viewing the peaks. Lastly the peaks were labeled by

selecting ‘label peak’.

4.10 The anvil was lifted and the sample was removed by using tweezers.

4.11 The steps 4.4-4.9 were repeated for other two samples.

4.12 The sample holder (ATR) was cleaned and removed from FTIR machine.

Page | 7

Polymer Properties (EBT 326) Exp. 4: FTIR

5.0 RESULT AND DISCUSSION

Figure 8: composite, alumina, PP spectrum analysis

Figure 8 is the infrared spectrum of the samples that we had been conducted in this

experiment. The Y-axis was showing the percentage of the transmitted infrared light of the

compound inside the specimen and the X-axis showing their wavelength (λ). There were three

conditions and three spectrums showing on this figure, pure polypropylene, alumina, and

PP/alumina composite.

In plain view, we can see from the composite spectrum is more smooth compared to the

alumina and PP spectrum. Composite which has combination of two other material; alumina and

PP shows few smooth peaks compared to alumina and PP which have many peaks which means

it has many several functional groups inside it.

Page | 8

Polymer Properties (EBT 326) Exp. 4: FTIR

Table 1: Highest, intermediate and lowest peak values of three samples

Sample Highest peak (cm-1) Intermediate peak (cm-1) Lowest peak (cm-1)

PP 2914.67 997.89 3426.16

Alumina 837.35 1537.35 2926.58

Composite 2923.44 1456.54 1657.29

The highest peak, 2914.67 cm-1 for pure PP was at based on Table of Characteristic IR

Absorptions [Appendix] meaning that in this peak pure PU has C–H stretch which is functional

group of alkanes. While the intermediate peak was in 997.89 cm-1 which means it has =C–H bend

and belongs to alkenes functional group. And as the lowest peak of pure PP with frequency of

3426.16 cm-1 has O–H stretch and H–bonded which is functional group of alcohols and phenols.

For the alumina, the highest peak has frequency of 837.35 cm-1 which has C–Cl stretch

bond and functional group of alkyl halides. With frequency of 1537.35 cm-1 the intermediate

peak has N–O asymmetric stretch and belongs to nitro compounds functional group. And the

lowest peak has frequency of 2926.58 cm-1 and belongs to alkanes functional group that has C–H

stretch bond.

As for 7 wt% PP/Al2O3 composite, it is a composite with combination of both other

samples; PP and alumina which make the composite has smoother spectrum compared to the

main combination materials. Having the highest peak frequency in 2923.44 cm-1 almost same as

the highest peak of PP and lowest peak of alumina, the peak has C–H stretch bond and functional

group of alkanes. Meanwhile the intermediate peak has frequency of 1456.54 cm-1 has alkanes

and C–H bend bond. Lastly the lowest peak frequency is 1657.29 cm-1 has –C=C– stretch which

belongs to alkenes functional group.

Page | 9

Polymer Properties (EBT 326) Exp. 4: FTIR

6.0 CONCLUSION

Based on the experiment that has been conduct, we can prove that the functional group of

polymeric materials and polymeric blends can effect the structure pattern of infrared

spectrum of the material tested. We can see the effect through the value of peak on every

spectrum line graph that obtain from the FTIR spectroscopy machine.

7.0 REFERENCES

[1] Dr Norzilah Abdul Halif. Fourier Transform Infrared Spectroscopy (FTIR),

Universiti Malaysia Perlis, Perlis, 2015. [Lectures]. Available: UniMAP Portal,

http://portal.unimap.edu.my [accessed on 3 Nov. 2015].

[2] Mrs Anis Sofia Sufian and Dr Mohd Firdaus Omar, Laboratory Manual for

Polymer Properties, Universiti Malaysia Perlis, Perlis, 2015. [Lectures]. Available: UniMAP

Portal, http://portal.unimap.edu.my [accessed on 1 Nov. 2015].

[3] Chemical Organization Colorado (2003). IR Chart [Online]. Available:

http://orgchem.colorado.edu/Spectroscopy/specttutor/irchart.html [Accessed Nov. 6, 2015].

[4] Available: http://mmrc.caltech.edu/FTIR/FTIRintro.pdf [Accessed Nov. 6, 2015].

Page | 10

Polymer Properties (EBT 326) Exp. 4: FTIR

8.0 APPENDIX

Page | 11