www.ij-ms.org International Journal of Material Science (IJMSCI) Volume 3 Issue 4, December 2013 doi: 10.14355/ijmsci.2013.0304.04 152 Compatibility in Immiscible Poly(Vinyl Chloride)/Poly(Styrene) Blends V. D. Deshpande *1 , Pravin Pawar 2 , Vinod Gokarna 3 1,2,3 Department of Physics, Institute of Chemical Technology, India *1 vindesh2@rediffmail.com ; 2 pravinpawar@gmail.com; 3 py07vs.gokarna@pg.ictmumbai.edu.in Abstract The morphology, orientation and mechanical studies of solvent cast poly (vinyl chloride) (PVC) /poly (styrene) (PS) blend films were carried out for various concentrations and draw ratios. Samples of pure PVC, PS and its blends were prepared using standard solution casting method. The thermal studies revealed that PVC/PS blends remain ‘incompatible’ for the compositions PVC/PS-80/20, 60/40, and 30/70; compatibility is suggested for the compositions PVC/PS-20/80, 10/90 and 05/95. Microscopy results indicate that PVC/PS 20/80, 10/90 and 05/95 blends show uniform distribution of PVC dispersed phase in PS matrix phase. Orientation studies showed that PVC/PS-20/80, 10/90 and 05/95 blend compositions gave a systematic change in orientation function with draw ratio; matching with their respective pure forms; while all other blend compositions indicate independent random orientation behaviour. The mechanical properties like storage modulus and tensile strength of the blends PVC/PS-20/80, 10/90and 05/95 are very close to pure PVC. The blends 80/20, 60/40, and 30/70 showed inferior properties to pure PVC for all draw ratios. The results were explained in terms of morphology of the blends. Keywords PVC; Immiscible; FTIR; PS Introduction Molecular orientation of uniaxially stretched polymer blends has been the subject of several studies. The orientation of polymer chains, one of the important factors affecting the mechanical properties of polymers, in a blend is an attractive study because in a blend two components may possibly orient in different ways leading to the formation of a new superstructure. Several techniques exist for evaluation of such behaviour e.g. X-ray Diffraction, Birefringence, Sonic Modulus, Polarized Raman Spectroscopy and Infrared Spectroscopy. Most of the studies of the orientation behaviour have been carried out on ‘compatible’ blends. Chabot and Prudhomme studied the segmental orientation in PVC and poly (α-methyl-α–n-propyl-β- propiolactone) (PMMPL). Deshpande and Singh have shown the effect of miscibility on orientation in PVC and poly (methyl methacrylate) (PMMA) blends. The segmental orientation in PVC with polycaprolactone (PCL) and nitrocellulose (NC) were studied by Hubbell and Cooper. Keroacka, et al studied the effect of molecular orientation in crystalline and amorphous phases for PVC/PCL blends. These polymers were fully or partially miscible with PVC. There have been very few studies on the orientation behaviour of immiscible polymer blends. In most of the cases, it is observed that the major component orients to higher degree than the minor dispersed component, which is again dependent on the stretching temperature. The resultant morphology has a significant effect on the overall deformation behaviour. The blend of interest in this study is PVC /poly (styrene) PS; and PVC/PS blends are reported immiscible due to unfavourable interactions. This would affect the morphology by means of controlling the domain size. In the present studies, PVC/PS blends have been prepared with different compositions in the film form using solution casting method. The objective of the present work was to investigate the influence of morphology of blends on the orientation and mechanical properties of the blends and to gain further understanding of the orientation behaviour in the multiphase incompatible polymer blends. Experimental Materials The analytical grade polymers, PVC with Mw of 94,000 and ρ=1.40 g/cm 3 ; PS with Mw of 100,000 and ρ=1.05 g/cm 3 obtained from Aldrich Chemical Co. were used in this study. The samples of pure PVC, PS and PVC-PS blends were prepared using standard solution casting method. First of all, the two polymers were mixed in proportions as PVC/PS-100/00, 80/20, 60/40, 30/70, 20/80, 10/90, 05/95 and 00/100. Keeping the total