Characterization of interfaces in Poly (styrene-co-acrylonitrile) (SAN) based ternary polymer blends: A new approach from positron lifetime spectroscopy

Positron lifetime spectroscopy is used to develop a new approach to characterize the individual interfaces in ternary polymer blends and hence determine composition dependent miscibility level. This approach has its genesis in KSR and KRZ models for the evaluation of hydrodynamic interaction parameters (αij). The method successfully applied for binary blends (single interface) earlier is theoretically modified for ternary blends and experimentally verified by measuring free volume content in blends and their constituents. We have tested the efficacy of this method in two ternary blends namely SAN/PVC/PMMA and SAN/EVA/PVC at different compositions. The effective hydrodynamic parameter αeff evaluated using individual α values turns out to be handy in predicting the overall miscibility level of a ternary blend. Results show that SAN/PVC/PMMA exhibits maximum αeff of −9.67 at composition 75/5/20 and SAN/EVA/PVC shows −3.18 at 50/35/15 indicating that miscibility level is high at these compositions for these two blends. DSC and SEM studies have also been used to supplement positron results

Construction of concentration density profile across the interface in SAN/EVA immiscible blend from positron lifetime parameters

The interface width determination through the construction of composition density profile across the interface in an immiscible binary polymer blend using ortho-positronium lifetime parameters is described in this paper. The distribution of free volume and hence the hydrodynamic interaction parameter has been evaluated for this purpose making use of the CONTIN routine analysis of the lifetime spectra. The results showed the broad free volume distribution and narrow interface width were reminiscent of lack of interaction between SAN and EVA the constituents

Interface profile studies in immiscible and partially miscible binary polymer blends from free volume measurement

The diffused interface widths in an immiscible and a partially miscible polymer blend namely Polyvinyl chloride/Ethylene vinyl acetate (PVC/EVA) and Polystyrene/Polymethylmethacrylate (PS/PMMA) are experimentally measured and reported here. A new empirical relation found between hydrodynamic interaction parameter derived from free volume data and the Flory-Huggins interaction parameter is used to construct density profile across the interface to derive the interface width in above two binary blends

Positron annihilation lifetime study of interfaces in ternary polymer blends

A new method based on positron lifetime spectroscopy is developed to characterize individual interfaces in ternary polymer blends and hence determine the composition dependent miscibility level. The method owes its origin to the Kirkwood-Risemann-Zimm (KRZ) model for the evaluation of the hydrodynamic interaction parameters (αij) which was used successfully for a binary blend with a single interface. The model was revised for the present work for ternary polymer blends to account for three interfaces. The efficacy of this method is shown for two ternary blends namely poly(styrene-co-acrylonitrile)/poly (ethylene-covinylacetate)/poly(vinyl chloride) (SAN/EVA/PVC) and polycaprolactone /poly(styrene-coacrylonitrile)/poly(vinyl chloride) (PCL/SAN/PVC) at different compositions. An effective hydrodynamic interaction parameter, αeff, was introduced to predict the overall miscibility of ternary blends

Information on individual interfaces in ternary polymer blends from positron annihilation lifetime studies

Positron Annihilation Lifetime Spectroscopy has been used to determine the free volume content in the ternary blends of SAN/EVA/PVC. The method of deriving hydrodynamic interaction parameter (α) in binary polymer blends was modified for ternary polymer blend system characterized by three distinct interfaces. Each interface characterized, is associated with an α and its assertion for the ternary blend are compared with available literature data

Photo-degradation of Lexan polycarbonate studied using positron lifetime spectroscopy

The free volume properties of pristine and UV irradiated Lexan polycarbonate have been investigated using Positron Lifetime Spectroscopy (PLS). The decrease in o-Ps life time and free volume size of irradiated sample is attributed to free volume modification and formation of more stable free radicals. These free radicals are formed due to the breakage of C-O bonds in Lexan polycarbonate after irradiation. This is also supported by the decrease in the intensity of C-O bond after exposure to UV-radiation as studied from Fourier Transform Infrared (FTIR) spectroscopy and it also shows that benzene ring does not undergo any changes after irradiation

Influence of nanopores on molecular polarizability and polarization currents in epoxy nanocomposites

Epoxy resin based nanocomposites with silica (SiO2), alumina (Al2O3) and zinc oxide (ZnO) as nano fillers were fabricated to investigate the relationship between the polarization and depolarization current. The polarization and depolarization current, charge carrier mobility, absorption current and nano size free volume cavities of nano dielectric epoxy composites and their interrelation are discussed. It is observed that the current magnitude increases in the three nanocomposites with loading of nano SiO2, Al2O3 and ZnO and the peak width of each composite is greater than that of pure epoxy. Free volume studies are carried out using positron annihilation lifetime spectroscopy (PALS). From the results it is observed that molecular polarizability decreases and charge carrier mobility increases with the incorporation of SiO2, Al2O3 and ZnO loading. This trend is typical in Al 2O3, whereas in case of SiO2 the molecular polarizability is unaffected and with ZnO, molecular polarizability and charge carrier mobility decrease above 10 wt% filler. The Al2O3 nanofillers are structurally different as compared to SiO2 and ZnO fillers. It is observed that Al2O3 has more influence on polarizability of the composite

A new insight into interfaces of immiscible binary polymer blends from the free volume approach

The interface width in an immiscible (PVC/PS) polymer blend is determined using hydrodynamic interaction parameter (α) derived from free volume data measured using Positron lifetime spectrometer. CONTIN program has been employed to get the free volume hole size distribution. A new definition of interface width is presented, which originates from the Kirkwood-Riseman theory and friction coefficient as per Stokes equation. Friction at the interface of a binary blend decides how close the surfaces come or stay farther resulting in narrow or broad interface width respectively

Positron annihilation lifetime study of interfaces in ternary polymer blends

A new method based on positron lifetime spectroscopy is developed to characterize individual interfaces in ternary polymer blends and hence determine the composition dependent miscibility level. The method owes its origin to the Kirkwood-Risemann-Zimm (KRZ) model for the evaluation of the hydrodynamic interaction parameters (αij) which was used successfully for a binary blend with a single interface. The model was revised for the present work for ternary polymer blends to account for three interfaces. The efficacy of this method is shown for two ternary blends namely poly(styrene-co-acrylonitrile)/poly (ethylene-covinylacetate)/poly(vinyl chloride) (SAN/EVA/PVC) and polycaprolactone /poly(styrene-coacrylonitrile)/poly(vinyl chloride) (PCL/SAN/PVC) at different compositions. An effective hydrodynamic interaction parameter, αeff, was introduced to predict the overall miscibility of ternary blends