Study The Electrical Properties of PS-CaO Composites


Majeed Ali Habeeb, Ahmad Hashim and Bahaa H. Rabee
Babylon University, College of Education , Department of physics, Iraq.
E-Mail: ahmed_taay@yahoo.com



Abstract

(PS-CaO) composites have been prepared by using casting method with different weight percentages of CaO. The A.C electrical properties (dielectric constant, dielectric loss factor and A.C electrical conductivity ) of PS-CaO composites have been studied. The results show that the dielectric constant and dielectric loss factor decreases with increasing of frequency while A.C electrical conductivity increase with increasing of frequency . Also , dielectric constant , dielectric loss factor and A.C electrical conductivity of composites increases with increasing of weight percentage of CaO .
keywords : polystyrene , composite , electrical properties

Introduction
Plastics are the most versatile materials used indifferent chemical industries , such as aircraft , packaging , electrical equipment and as electrical insulators. They have increasing important role in the manufacture of satellites , space researches and thermal barriers. Plastics have replaced metals in many application. they have superseded steel and many other metals in being erosion resistant and chemically inert. Having higher temperature extension and specific heat than metals[1,2]
Poly styrene is a thermoplastic made from the aromatic monomer styrene as its basic unit. It is a transparent glass –like substance which does not dissolve in acids or alcohol , but dissolve in aromatic hydro carbons , benzene and esters . it is melting point is 239 C, glass transition temperature is 100 C and density is 1.05 gm/cm3 [3,4,5]
Polystyrene is synthesized under different polymerization condition depending on the final application of the polymer[6]. It is does not stretch or shrink , used in the manufacture of plates and cables because it is a good electrical insulator, it is also used in the manufacture of rubber and household articles [2,4].



Experimental Procedure
The materials used in this paper is PS as matrix and CaO as a filler. The electronic balanced of accuracy 10-4 have been used to obtain a weight amount of PS and CaO the weight percentages of CaO are (0,3,5,7,10) wt .% . The samples prepared by using casting method , the solution was poured into a clear glass plate dishes and dried for 48 hours’ , the thickness of this samples were about 10 µm.
The A.C electrical properties measured by using (impedance analyzer 6500 B series) ,the measured capacitance C(w) was used to calculate the dielectric constant ?(w) using the following relation [7,8,9]
? = c(w)d/?o A ……………..…..(1)
where d is the sample thickness and A is the surface area of the sample
Whereas dielectric loss factor ?" (w) can be found from the formula:
?"(w) =?(w) ? tan ? (w) ………………...(2)
where tan ? (w) is dissipation factor
The A.C electrical conductivity (?ac) can be calculated by the following equation:
?ac(w) =?o w ?" …………………………..(3)
where ?o is the permittivity of free space and w is the angular frequency (w=2? f)

Results and Discussion

The variation of dielectric constant for PS-CaO composites as a function of frequency at room temperature is shown in figure(1) , from this figure one can be see that the dielectric constant decrease with increasing of frequency , because the increase of frequencies results in decreasing of space charge polarization[10].

Figure(1) The relation between dielectric constant and frequency

Figure(2) shows dielectric constant as a function of concentration of calcium oxide at room temperature and 100 HZ. The increase in dielectric constant with weight fraction of CaO due to increase the charge caries where the calcium oxide particles at low concentrations are represented by small darker regions and become large when the calcium oxide content increases and the net work will be connected to each other containing the overlapping paths to allow the charge carriers to pass through[11].


Figure(2) The relation between dielectric constant and filler concentration

The relation between dielectric loss factor and frequency is shown in figure (3) the values of dielectric loss factor are decreasing with increasing of frequency this is due to some relaxation processes with usually occur in heterogeneous system [12].

Figure(3) The relation between dielectric loss and frequency

The variation of dielectric loss factor with calcium oxide concentration is shown in figure (4) , this figure shows increasing of dielectric loss factor by in creasing of calcium oxide , this is due to the overlapping of relaxation process which are attributed to some structural charges that take place in the composite as result of filler concentration [13].

Figure(4) The relation between dielectric loss and filler concentration

The behavior of A.C conductivity of PS-CaO composite for various concentration of the filler as a function of frequency at room temperature is shown in figure(5) , from this figure we can see that the conductivity increases by increases of frequency , this is happened due to polarization effect and hopping where the polarization effect between finite network as well as hopping of the electron between adjacent states, randomly distributed with in these finite network [14].

Figure(5) The relation between electrical conductivity and frequency

The variation of A.C electrical conductivity with weight filler content at 100 Hz is shown in figure (6) , the electrical conductivity increases as a result of increasing of charge carriers oxide content[15].

Figure(6) The relation between electrical conductivity and filler concentration


Conclusion
The dielectric constant and dielectric loss factor decreases with increasing of frequency , while , A.C electrical conductivity increase with increase of frequency , on the other hand , the dielectric constant , dielectric loss factor and A.C electrical conductivity increases by increasing of filler concentration.

References
[1] G.Kontos, A.Soulintzis and P.K. Karahaliou,2007, “J. Express Polymer Letters”,Vol.1,No.12,P.(781-789)
[2] S. Mustafa,2008, “Engineering Chemistry”, Library of Arab society for
Publication and Distribution, Jordan
[3] M. Dahshan,2002, “Introduction to Material Science and Engineering”, 2nd Ed.
[4] T.Beraada, G. Al-Adam,1989, “The Updated Chemistry of Large Molecules”.
[5] S.Mussa and F. Basheer,2003, “Materials Technologies”, Tripoli.
[6] G. Al-Adam and H.Ali,1983, “Technology and Polymer Chemistry”
[7] J. Y. Seto.,1975 “J. Appl. Phys”, Vol.46, No.12
[8] A. K. Batabal,1984, “Thin Solid Films”, Vol.112, p.(51)
[9] A. Von. Hippel,1967,” Handbook of Physics”, Mc-Graw. Hill 2nd Edition,Chap.7
[10] M. Hamzah , E. Saion , A. Kassim , E. Mahmud and I. Shahrim , 2009, “J. for the advancement of Sci.”, Vol. 1, No. 1,P. 9-14 .
[11] N. K. Srivastava and R. M. Mehra, 2009, “ J. Materials Science- Poland”, Vol. 27, No.1
[12] G .A. kontos ,A.L. Soulintzis and p.k. karahaliou , 2007 , "J. express polymer letters , Vol .1,No.12, p.(781-789)
[16] M.H.Harun and A. kassim ,2008 , "Malaysim Polymer Journal ", Vol .3, No.2, pp. (24-31) .
[13 ]T.K. Vishnuvardhan ,2006, "Brazil Bull.Mater.Sci.”,Vol .29,No.1, p.(77-83)
[14] Ahmed M. S. and Zihilif A. M. , 1992, " J. Mater. Sc.”,Vol.25,No.706
[15] S. Sreehartha , T.F. Sunder , V.R. Siddhara and R. Vasanthakumari, 1988 , "J. of Applied Polymer Science", Vol. 36, p. (1607-1615).