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Middle East Journal of Applied
Sciences
ISSN 2077-4613
Volume : 05 | Issue : 05 | Oct.-Dec. | 2015
Pages: 36-44
FTIR and UV/Vis. Spectroscopy: A Key for Miscibility Investigation of PVC/PMMA
Polymer Blend
1
A. M. Abdelghany, 2E. M. Abdelrazek, 2A. ElShahawy and 2A. A. Al-Muntaser
1
Spectroscopy Department, National Research Center, 33 Elbehouth St., Cairo, 12311, Egypt
Physics Department, Faculty of Science, Mansoura University, Mansoura, 35516, Egypt
2
ABSTRACT
Fourier transform infrared (FTIR) and UV/Visible (UV/vis.) spectroscopy measurements for Polyvinyl
chloride/polymethyl methacrylate (PVC/PMMA) blends prepared in tetrahydrofuran at room temperature were
measured. These measured spectra were then used to evaluate the optical energy gap in relation to blend
composition. X-ray diffraction (XRD) was used to identify the molecular interaction arising in the mentioned
polymer blend films. The peculiar deviation confirms the structural changes in the prepared samples. Scanning
electron microscopy shade light on the type of interaction by retracing of the band of Carbonyl group at 1732
cm-1. The change of full width at half maximum and area under carbonyl band in FTIR spectrum was found to
change drastically with composition.
Keywords: PVC/PMMA blend: FTIR: UV/Vis.: miscibility and SEM.
1. Introduction
In last decades, polymer blends received much experimental attention both in academic as well as on
industrial perspective due to their unique characteristics such as low manufacturing cost, low density and ability
to form thick and thin samples, versatile electrical and optical properties (Bhavsar and Tripathi, 2014). In
addition, polymer blending is a useful technique for designing materials with a variety of properties suitable for
specified applications due to collective properties of each constituent compared to the properties of each
individual component polymer (Rhoo et al., 1997; Oh and Kim, 1999; Pielichowski, 1999; Stephen et al., 2000;
Tang and Liau, 2000; Pielichowski and Hamerton, 2000; Robeson, 2014). Blending is cost effective way and
more often a faster to get the required properties than synthesizing new polymers (Dixit et al., 2009).
Polyvinylchloride (PVC) is an important commercial polymer because of its wide range of applications
(Saeed and Hassan, 2014). It was used as a general commodity plastic owing to its low cost and recoverability,
excellent electrical and corrosion resistance. However, its low impact strength and thermal stability limits its
applications (Bhattacharyya et al., 2014). Several polymers are mixed with PVC as plasticizers or processing
aids (Reyne, 1992).
PMMA is widely used in many technological applications because of its unique combination of
excellent optical properties with chemical inertness, some good mechanical properties, thermal stability,
electrical properties, weather resistance and easy shaping (Silva et al., 2010; Gilman, 1999).
Ramadan et al. (2014) added PVC to PMMA to overcome the problem of rigidity of single polymer
and they observed that resultant blends were soft and open to more uses and applications. Many authors
(Vorenkamp et al., 1985; Soman and Kelkar, 2009; Ramesh et al., 2007; Gaurang et al., 2010; Saq’an et al.,
2001) suggested that interaction between PMMA and PVC occurred via hydrogen bonding type of specific
interaction involving -hydrogen of PVC and the carbonyl group of PMMA. The changes in the values of the
optical energy gaps, dielectric constants, and the refractive index under different frequencies and blending ratio
were related to the effects of structural changes in the amorphous domains, impurities, and space charge existing
in the interfaces between the mixed phases (Belsare et al., 2011; Kamira and Naima, 2006; Khan et al., 2008).
The study of the Tg versus composition of PMMA/PVC shows a strong interaction between PMMA and PVC
and the modulus of elasticity is dramatically influenced by composition and follows a synergic behavior and it
can be concluded that the increase in the PVC content enhances the toughness of PMMA/PVC blend (Ramadan
et al., 2013; Arinze et al., 2013).
In the present work samples of different mass fractions (PMMA/PVC) were prepared and their physical
properties were studied by ordinary FTIR, XRD, UV/Vis and SEM with different glimpse. A new route for
inquest the degree of miscibility was introduced depending on a spectroscopic quantitative measurement.
Corresponding Author: A.M. Abdelghany, Spectroscopy Department, National Research Center, 33 Elbehouth St., Cairo,
12311, Egypt.
Tel: +201157962044; Fax: +20502246781 E-mail: [email protected]
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Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
2. Experimental Work:
2.1. Sample Preparation:
Samples of nominal composition x PVC- (100-x) PMMA (x= 100, 90, 80, 70, 60 and 40 wt%) were
prepared (Table 1). High molecular weight polyvinyl chloride (PVC) supplied by (Fluka) and powdered poly
methyl methacrylate (PMMA) supplied by (poly science, Warrington, PA) with molecular weight MW=
25000gm/mol were dissolved in tetrahydrofurane (THF) with purity 99.5% from (Central Drug House, New
Delhi, INDIA). Further increase in PMMA concentration leads to more brittle polyblend with difficult handling.
So, the concentrations were limited to the above mentioned ratios.
Table 1: Designations and compositions of PVC–PMMA polymer blend.
Designation
PVC(wt.%)
Pure PVC
100
B1
90
B2
80
B3
70
B4
60
Pure PMMA
0
PMMA (wt.%)
0
10
20
30
40
100
2.2 Measurement Techniques:
FTIR absorption spectra were carried out for different films using the single beam Fourier transform
infrared spectrometer (Nicolet iS10, USA) at room temperature in the spectral range of 4000-400 cm-1. X-ray
diffraction scans were obtained using PANalyticalXPert PRO XRD system using CuKα radiation (where, λ =
1.540 Å, the tube operated at 30 kV, the Bragg’s angle (2) in the range of (5˚-80˚). UV-Vis absorption spectra
were measured in the wavelength range (200-900) nm using (JASCO 630, Japan) spectrophotometer.
Morphology of prepared films was characterized using scanning electron microscope model (JEOLJSM6510LV, USA), at 20 kV accelerating voltage, magnification 500X.
3. Results and Discussion
3.1. Fourier Transform -Infrared Analysis:
FTIR absorption spectra were recorded in the wave number range (4000-400) cm-1 and presented in
Figure (1). The obtained spectrum was similar to that reported by Soman and Kellar (2009), Ramesh et al.
(2007) and Gaurang et al (2010). Characteristic absorption bands of both polymers (PMMA and PVC) can be
recognized and assigned.For PMMA, -CH2symmetric stretching vibrational mode observed at 2951cm-1, and a
band at about 1732 cm-1 corresponds to C=O stretching, CH3 stretching mode at 1446cm-1, –OCH3 vibrations at
1194cm-1and C-O stretching at 1143cm-1. The observed bands at 2951, 1732, 1446,1194 and 1143 cm-1 are
assigned to C-H stretching, CH2 deformation, CH-rocking, trans C-H wagging, C-Cl stretching and cis C-H
wagging characterizing PVC respectively. Table 2 represent the assigned vibrational band for polymeric
samples.
Table 2: Vibrational band assignments for pure PMMA and pure PVC.
Modes of vibration
-CH2 symmetric stretching
C=O stretching
CH3 stretching
-OCH3 stretching
C-O stretching
-CH stretching
-CH2 deformation
CH rocking
trans C-H wagging
C-Cl stretching
cis C-H wagging
Wavenumbers (
2951
1732
1446
1194
1143
2914
1329
1252
963
839
617
)
References
[17,18,19]
[17,18,19]
[17,18]
[17,18]
[19]
[17,18,19]
[17,18,19]
[17,18,19]
[17,18,19]
[17,18,19]
[17,19]
Figure (2) reveals FTIR absorption spectra of different mass fractions of PVC/PMMA polymer blends.
The vibrational band position changes correlated to their assignments were listed in Table 3.It is clear that there
is a minor change in the relative intensities of some characteristic vibrational bands. Complexation may shift the
polymer peak frequencies. FTIR would be sensitive both in situations where the complexation has occurred in
crystalline or amorphous phase.
This miscibility between PVC and PMMA is due to a specific interaction of hydrogen bonding type
between carbonyl (C = O) of PMMA and hydrogen from (CHC1) groups of PVC, as evidenced by FTIR
spectroscopy (Sah and Gupta, 2013). This is supported by the change of full width at half maximum and the
area under carbonyl band in FTIR spectrum. Correlation behavior between these factors and composition was
37
Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
Absorbance
introduced in Figures (3), (4) respectively, in which a strong interaction between PVC and PMMA was observed
in to be at sample B3.
Pure PVC
Pure PMMA
4000
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm )
1732
Fig. 1: FT-IR spectra of pure PMMA and pure PVC.
PM M A
Absorbance
B4
B3
B2
B1
PVC
4000
3500
3000
2500
2000
W ave num ber cm
1500
1000
500
-1
Fig. 2: FT-IR absorption spectra of prepared samples.
Table 3: Peak position and assignment for the vibrational modes observed in PVC/PMMA blends.
Description of vibration
Wavenumbers (
B1
B2
-CH stretching
2915
2918
-CH2 deformation
1329
1329
CH rocking
1249
1248
Trans C-H wagging
964
965
C-Cl stretching
841
844
cis C-H wagging
618
622
-CH3 stretching +
2970
2950
-CH2 symmetric stretching
C=O stretching
1731
1731
CH3 stretching
1432
1434
-OCH3 stretching
1194
1192
C-O stretching
1153
1152
)
B3
2914
1333
1244
966
842
616
2949
B4
1329
1245
968
845
622
2950
1732
1435
1193
1151
1732
1438
1191
1151
3.2. X-ray diffraction:
XRD analysis is very useful to investigate the structure of the polymeric materials and it enables us to
find out whether a material is crystalline or amorphous.
Figure (5) shows XRD pattern for pure samples of PVC, PMMA and different mass fractions of their
polyblend. Pure PMMA shows a broad diffraction peak at 2θ = 14°, typical of an amorphous material, together
with two bands of lower intensities centered at 29.7° and41.7°. This result was in agreement with previously
published by different authors (Motaung et al., 2012; Kamaraj et al., 2014). In addition, XRD of pure PVC
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Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
shows a broad peak, halo, in the region of 2θ=(15°–35°), indicating the amorphous nature of PVC as previously
reported (El Sayed et al., 2014).
Characteristic peaks of both PMMA and PVC were overlapped and shifted to 2θ = 41.7° indicating
some type of interaction and complexation of such polymers which explains the miscibility of all ratios as
indicated in previous work due to the change in crystallographic organization.
B1
B2
B3
B4
PVC%
90
80
70
60
1660
1680
1700
1720
1740
1760
1780
1800
-1
Wavenumber ( cm )
Fig. 3: Carbonyl stretching vibrations of PMMA in blend with PVC at room temperature.
55
1.0
50
45
0.9
Relative area
-1
FWHM (cm )
40
35
30
25
0.8
0.7
0.6
20
15
0.5
10
0
0
10
20
30
10
40
20
30
40
PM M A content (w t.% )
P M M A c o n te n t ( w t .% )
(a)
(b)
Fig. 4: PMMA concentration as a function of (a) FWHM, (b) relative area of carbonyl band.
Intensity (a.u.)
PMMA
B1
B2
B3
B4
PV C
10
20
30
40
50
60
70
80
2   d egree)
Fig. 5: X-ray diffraction scans of pure PVC, pure PMMA and
PVC/PMMA.
39
blend with different concentrations of
Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
Absorbance
3.3. UV/Vis. Optical studies:
The variation of absorption with wavelength optical n the range (200-900) nm for polymer blends.
Figure (6) shows absorption spectrum in the rang (200-900) nm reveals an absorption band at about
260 nm may be attributed to  → * which comes from unsaturated bonds, mainly; C=O which observed in FTIR at about 1732cm-1 (Abdelrazek et al., 2008). For pure PMMA, B1, B2, B3, B4 and pure PVC, there is sudden
decrease in the absorption values observed above the limits.
PMMA pure
B4
B3
B2
B1
PVC pure
200
400
600
800
Wavelength (nm)
Fig. 6: UV/Vis. spectra of pure PVC and pure PMMA and the blends with different concentrations.
Measurement of the absorption spectrum is the most direct method to investigate the band structure of
polymers. In the absorption process, an electron is excited from a lower to higher energy state by absorbing a
photon of known energy. The change in the transmitted radiation can determine the type of possible electron
transitions. Fundamental absorption refers to band-to-band or exaction transition. The fundamental absorption
shows a sudden rise in the absorption, known as absorption edge, which can be used to determine the optical
band gap (Eg=hc/λ).
Absorption is expressed in terms of a coefficient α (absorption coefficient), which is defined as the
relative rate of decrease in light intensity.
The absorption coefficient α was calculated from the absorbance (A) where
.
α=
(1)
t is the sample thickness in (cm) .
Absorption coefficient can be related to the energy of the incident photon as follows:
(αhν) = β(hν − E ) for hν > E
(2)
(αhν) = 0 for hν < E
(3)
Where β is a constant related to electrical conductivity and energy level separation, r = 2 or 3 for
indirect allowed and forbidden transitions, respectively, and r=1/2 or 3/2 for direct allowed and forbidden
transitions, respectively (Abdelghany et al., 2012).
Davis and Shalliday (1960) reported that near the fundamental band edge, both direct and indirect
transitions occur and can be observed by plotting (h)2 and (h)1/2, respectively, as a function of energy (h),
where h is Planck's constant. Figure(7(a-b)), shows a plot of (h)1/2 and (h)2 respectively, as a function of
photon energy (h), and can be used to calculate its optical energy gap. These values obtained are listed in Table
4.
3.4. Scanning electron microscopy:
Figure (8) shows the morphological structure for the prepared samples. Surface of pure PVC and Pure
PMMA was transparent, soft and a uniform morphology revealing smooth surfaces. After blending, the polymer
films containing lower concentration of PMMA content show a large number of very small sized pores as shown
in sample B1. These small pores are homogenously distributed. Polymer films containing higher content of
PMMA imageB2 exhibit larger sized pores which may be due to the coagulation of PVC during casting of
blends from its solvent. Then by increasing the content of PMMA to 30% image B3 and B4, the pores
disappeared and healing occures therefore apparently making the surfaces semi-soft this infers a good
complexation and compatibility between PVC/PMMA blend.
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Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
90
50000000
Pure PVC
80
Pure PVC
70
-2
40
2
(1/2)
h)
2
h) (cm eV )
1/2
50
(cm
-1/2
eV )
40000000
60
30
20
30000000
20000000
10000000
10
0
0
3
4
5
3
6
4
5
6
heV)
heV)
160
5.00E+008
B3
140
B3
4.00E+008
1/2
eV )
120
-2
2
80
60
2
h)
(1/2)
(cm
-1/2
h) (cm eV )
100
40
3.00E+008
2.00E+008
1.00E+008
20
0
3
4
5
6
0.00E+000
3
heV)
4
5
6
heV)
6000000
Pure PMMA
50
Pure PMMA
5000000
4000000
2
h) (cm eV )
h)
-2
30
3000000
2
(1/2)
(cm
-1/2
1/2
eV )
40
20
2000000
10
1000000
0
3
4
5
0
6
3
heV)
Fig. (7-a): Plot of (h1/2as a function of photon
energy (h)
4
5
6
heV)
Fig. (7-b): Plot of (h2, as a function of photon energy
(h)
Table 4: Direct and indirect optical Energy gap for PVC/PMMA blend films.
Sample
PMMA
Indirect transition
wt%
Eg1
Eg2
Pure PVC
0
3.95
4.76
B1
10
3.91
4.74
B2
20
3.75
4.69
B3
30
3.53
4.60
B4
40
3.57
4.64
Pure PMMA
100
3.92
4.58
41
Direct transition
Eg
5.294
5.247
5.220
5.186
5.200
5.000
Middle East J. Appl. Sci., 5(4): 36-44, 2015
ISSN 2077-4613
Pure PVC
Pure PMMA
B1
B2
B3
B4
Fig. 8: SEM micrograph of the surface of: pure PVC, pure PMMA, B1, B2, B3 and B4 of different concentrations
of PMMA at magnification 500 times.
Conclusions:
Polymer blend of PVC/PMMA with different concentrations were prepared and investigated. XRD
scan reveals the amorphous nature of PVC/PMMA polymer blends and proves that it was miscible at all ratios
with high degree of amorphousity for specified samples. FTIR shows minor variations in the peak intensity
without change in peak position. Results indicate that the vibrational bands at about 1732cm-1 assigned to C=O
stretching is sensitive to compositional changes. The degree of interaction and miscibility can be retraced by
observing the change in both FWHM and relative area under the Carbonyl group at 1732 cm-1. SEM proves the
homogeneity and miscibility of all ratios of prepared samples.
UV/Vis. Optical absorption data shows a change in the optical energy gap assuming both direct and
indirect transitions and prove that optical parameters of such blend was a compositional dependent.
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