Prediction of the Behavior for Polymer Blends Using Thermodynamic Model

Two polymer blends were prepared. The first one was Poly methyl methacrylate (PMMA) and Poly vinyl acetate (PVAc), and the second was Poly vinyl chloride (PVC) and Polystyrene (PS). The first blend prepared by mixing two polymers (PMMA, PVAc) with co-solvent (Chloroform) at different weight percentages (0/100, 20/80, 40/60, 50/50, 60/40, 80/20, 100/0). The second blend prepared by mixing two polymers (PVC, PS) with co-solvent N,N dimethylacetamide (DMAC) at different weight percentages (0/100,20/80,40/60,50/50,60/40,80/20,100/0). Two processes were used for preparation; dissolution process was used at a room temperature (25°C) and (1atm.) pressure using co-solvent. Viscosity test was performed for stock solutions (1%wt/v=1g/dL) and other concentrations (0.75, 0.6, 0.5, 0.4, 0.3 g/dL) these concentrations are obtained by dilution of stock solution. The obtained data were collected and substituted accordance to equations (Huggins Equation) and certain criteria (Interaction parameters ΔB,μ ) to identify the miscibility (or compatibiliIty).To get polymer blends in solid state, The same procedure to prepare the stock solution of diluted solutions followed but the stock solutions of polymer blends were at concentration (10%wt/v) for all different compositions and then followed solvent casting ( evaporation then drying). The solid state samples were taken to hold tests of DSC and FTIR. The aim of the present work was to study the thermodynamic behavior of polymer blend via determination of miscibility. Miscibility (or immiscibility) tests are performed in three techniques: viscometry method, DSC analyzer and FTIR to test polymer blend in solid state. It was found from the viscosity method that for first blend (PMMA/PVAc), the interaction parameters (ΔB,μ) are positive for all compositions therefore the system is miscible whilst the second system (PVC/PS) is immiscible where the interaction parameters (ΔB,μ) are negative. Differential scanning colarimetry (DSC) analyzer gave thermogram curves revealing one glass transition temperature for PMMA/PVAc blends except at (20/80) composition, this indicates that the system is miscible except at (20/80) composition. But, PVC/PS blends showed two glass transition temperatures so the system is immiscible. FTIR analysis for PMMA/PVAc blends depicted a weak interaction between the two polymers and solvent due to the miscibility establishment, whilst for PVC/PS blends, there was no interaction between two polymers to establish the miscibility, this indicates immiscible system. Calculations of Flory –Huggins interaction parameter for two systems was performed and the results pointed to miscible blend for PMMA/PVAc blends and immiscible blend for PVC/PS blends. So there is a good agreement between the experimental results and calculations of interaction parameter based on Flory – Huggins theory