International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 5, May 2014
ISSN 2319 - 4847
Optical properties of Poly
(Vinyl chloride)/polystyrene blends
Asrar Abdulmunem Saeed & Mohammed Zorah Hassan
Mustansiriyah University- College of Science,
Baghdad, Iraq
Abstract
Poly (Vinyl chloride) (PVC)/polystyrene (PS) blends with different ratios were prepared by solvent casting from tetrahydrofuran
(THF). The absorption spectra of polyvinylchloride / polystyrene blends at different concentrations (PVC %, 75% PVC/25% PS,
50% PVC / 50%PS, 25% PVC/75% PS, % PS) showed absorption changes in the wavelength range, which depends on the polymer
type, and on the concentration of the polymer blends. It was found that 50 % PVC / 50 % PS ratio from these polymers showed
higher absorption values in comparison with the other blends. The absorption spectra has been recorded in the wave length range
(200 –1100) nm. The absorption coefficients (α), the extinction coefficient (K), refractive index (n) have been evaluated.
Key words: optical properties, PVC/PS blend, optical constants.
1- Introduction
Polymer blends are a mixture of chemically different polymers or copolymers with no covalent bonding between them.
Polymer blends are classified as three types, namely, homologous, miscible and immiscible blends. Chemically identical
polymers with different molecular masses constitute homologous polymer lends. Miscible polymer blends exhibit single
phase behavior and immiscible polymer blends exhibit two or more phases at all compositions and temperatures.
Preparation of polymer blends has been received considerable importance in the recent past owing to the shorter time and
lower cost of the product development than those of a new polymer [1]. The performance of a polymeric material can be
improved by selection of suitable ingredients and their ratios. Polymer blending imparts certain new characteristics
leading to the formation of new materials with enhanced physical, chemical and mechanical properties [2, 3]. Blending of
two polymers having different properties is usually producing a new polymeric material. These new polymeric material
mat possess the properties of both the polymers. The properties of polymer blends such as toughness, strength, etc have
close relationships with their internal micro phase morphology [4-6].
Polyvinylchloride has been found to form an immiscible blend with polystyrene. Miscibility is not a prerequisite for
blends applications; it is an easy way to design a new polymeric material. Polystyrene is a well-known amorphous
polymer with good thermal and radiation resistant properties. Polystyrene is available with a wide range of formulations.
The styrenic part may impart the properties like toughening, flame resistance and solvent resistance. Commercially
available polystyrene is mostly a tactic type and amorphous in nature. The use of polystyrene is limited because of its
susceptibility to degradation from UV radiation, chemical attack from aromatic, and chlorinated hydrocarbons may also
cause problem in application areas. Polyvinyl chloride is one of the most important commercial polymers that have wide
range of applications [7]. Polyvinylchloride is a linear, thermoplastic, substantially amorphous polymer, with a huge
commercial interest, due to the accessibility to basic raw materials and to its properties.
Polymeric materials have attracted the scientific and technological researchers, because of their wide applications.
Deshmukh, et al reported the optical transmission and UV-VIS absorption spectra in wavelength of (450-1000)nm with
different concentration of polyanline doped PVC-PMMA thin films, the absorption coefficient(  ), optical energy gap
(Eopt), refractive index(n) and optical dielectric constant had been evaluated. The effects of doping percentage of
polyaniline on these parameters had been discussed and nonlinear behaviors for all the parameters were investigated [8].
Burghate et al [9] studied the optical properties of PVC-PMMA polymer blends. Joshi et al [10] study the polyblend of
polyvinyl chloride (PVC) and polystyrene (PS) in the weight ratio 5:1 using (1.25 g) of PVC and (0.25 g) of PS by casting
method. Polyaniline (PANI) has been used as dopant and with (0.5%, 1.0%, 2.0% and 2.5%) of the total weight of the
polymers. On the basis of optical absorbance and transmittance measurements at normal incidence of light in the
wavelength range (500-1000) nm, the absorption coefficient, optical energy gap, refractive index, optical dielectric
constant and ratio of carrier concentration to the effective mass was reported for polyaniline doped PVC-PS blend. It was
found that the behavior of all the optical parameters found to be nonlinear.
V. Sangawar and N. Mohari[11] study the electrical, thermal and optical band gap of polypyrrole filled PVC:PMMA
thin films, they prepared polypyrrole by chemical oxidative method from pyrrole monomer using ammonium per sulfate
as oxidant and p-toluene sulphonic acid as a dopant. G. Patel et al [12] study PVC/PMMA polymer blends were
characterized by Fourier Transform Infrared Spectroscopy (FTIR), UV-VIS spectroscopy and mechanical analysis. The
changes in mechanical properties are reflected by the changes in the IR spectrum. The mechanical properties of such poly
blends revealed a substantial increase in Young modulus and ultimate tensile strength after initial drop at 10% of PMMA.
Volume 3, Issue 5, May 2014
Page 61
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 5, May 2014
ISSN 2319 - 4847
Optical properties such as the absorption coefficient, optical energy gap were calculated. The effects of different blending
percentage on these parameters have been discussed and their results are co-related with IR study.
In the present work, PVC/PS blends were prepared with different weight ratios to investigate the optical properties for
this
blend.
2- Experimental work
Commercial grades of PVC and PS were purchased from Modern Scientific Company, Coimbatore and used as received.
A series of polymer blends of PVC and PS were prepared from the common solvent tetrahydrofuran(THF) as follows
Polymer solutions were prepared by dissolving PVC/PS in various weight ratios (100/0, 75/25, 50/50, 25/75, 0/100 w/w)
in THF with thickness about(0.09, 0.095, 0.09, 0.1, 0.085) mm. The solutions were mixed at room temperature and
stirred for 4 hours. The solutions were then poured in to the glass plates and THF was slowly evaporated under ambient
conditions to form transparent films.
3- Results and Discussion
The optical constants are very important because they describe the optical behavior of the materials. The absorption
coefficient of the material is very strong function of photon energy and band gap energy. The variation of absorption with
wave length of the incident light were recorded by using (UV-VIS. Spectrometer, T70-80) in the wavelength optical range
(200 – 1100)nm for polymer blend.
Figure (1) show the absorption spectrum which reveals a strong absorption probability below (250 – 290)nm for (PVC % ,
75% PVC/25%PS, 50% PVC / 50%PS , 25% PVC/75% PS, % PS ) respectively .There is sudden decrease in the
absorption values observed above the limits. For (50% PVC/ 50% PS) the decrease was even slower. The (50% PVC /
50% PS ) blend showed high absorption than the other blends for polymer blend (PVC/PS) and all the films showed the
same behavior but the absorption was decrease at %PS.
Figure. (1): UV/Visible absorption spectroscopy of (PVC/PS) with wave length at different concentration
The sudden raises in absorption spectrum called absorption edge that can be used to determine the optical band gap from
calculate the absorption coefficient (α) [13, 14],
 = (2.303×A)/t
(1)
Where A: is the absorption of the material.
t: is the sample's thickness (cm).
Figure (2) show the relationship of the absorption coefficient with wave length of different weight percentages of
PVC/PS blends, it show light absorption edge for PVC, while it became less for PS.
Figure. (2): UV/Visible absorption coefficient of (PVC/PS) with wavelength at different concentration
The refractive index (n) and extinction coefficient (K) were calculated from the following equations, (eqs. (2 and 3)), and
plotted in figs. (3 and 4)[13, 15]:
Volume 3, Issue 5, May 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 5, May 2014
n
4 RR  1
R  12  K 2 R  1
ISSN 2319 - 4847
(2)
R: is the optical reflectance.
Figure (3) shows the variation of refractive index (n) as a function of wave length. In order to compare our results of
refractive index for PS with the published data, which were calculated at 600 nm. The value of (n) was found to be (1.85)
for thickness (20 µm), while Ahmed et al [16], obtained the value of (n= 2.13) with thickness (100 µm) and Papanu et al
[17] obtained (n= 1.48) with thickness (1µm) deposited on silicon wafer. The difference in (n) value is attributed to the
different in thickness.
Figure (3): variation of refractive index for (PVC/PS) blend with wave length.
Figure (4) shows the variation of extinction coefficient (
) with wave length (λ). The blend (50% PVC / 50% PS)
concentration has the highest value of (K) and it was displaced toward the long wavelength.
Figure (4): variation of extinction coefficient for (PVC/PS) blend with wavelength.
Table (1) : The parameters of optical constants for polymer blend (PVC / PS)
Polymer. system
α (cm-1)
n
10-4 ×K
PVC
172
2.01
3
75% PS/25% PVC
213
1.17
4.9
50% PS/50% PVC
186
1.82
4.3
25% PS/75% PVC
187
1.8
4.18
240
1.3
5.9
PS
4- Conclusion
1- Strong absorption clear between (200 – 290) nm.
2- 50% PVC / 50% PS blend showed the best optical properties.
3- The absorption coefficient, extinction coefficient, refractive index for (50% PVC / 50% PS) show significant
change from samples in compared with other blend samples.
Volume 3, Issue 5, May 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 5, May 2014
ISSN 2319 - 4847
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