Positron annihilation and differential scanning calorimetric study of poly(trimethylene terephthalate)/EPDM blends

Ravikumar, H. B.; Ranganathaiah, C.; Kumaraswamy, G. N.; Thomas, Sabu

doi:10.1016/j.polymer.2004.12.058

Cited by 86 publications

(72 citation statements)

References 23 publications

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“…The PALS technique and its instrumentation are well established [18][19][20][21][22][23][24][25][26]. Of relevance to polymers is the capture of an electron to form either para-positronium (p-Ps) if the positron and electron have aligned antiparallel spins or ortho-positronium (o-Ps) with parallel spins.…”

Section: Positron Annihilation Lifetime Measurements (Pals)mentioning

confidence: 99%

“…In other than free space, o-Ps picks up an electron from the surrounding medium and its lifetime is shortened. This localized annihilation in the "free-volume holes" [18] makes it the microprobe of choice since its lifetime and intensity become a measure of the electron density and free-volume size in the study of microstructural behavior of polymers [18][19][20][21][22][23][24][25][26].…”

Section: Positron Annihilation Lifetime Measurements (Pals)mentioning

confidence: 99%

“…Coincidence Doppler broadening spectroscopy is an established technique to measure and understand the chemical environment of materials at the site of positron annihilation with the measurement of momentum distributions of annihilation events with core/valence electrons. The well-established positron annihilation lifetime spectroscopy, particularly for polymers and polymer-based materials, concerns the free volume size and its distribution [18][19][20][21][22][23][24][25][26]. The high-momentum part of the Doppler-broadened annihilation spectra is used to distinguish different elements because the core electrons retain their atomic character even when atoms form a complex polymer.…”

Section: Introductionmentioning

confidence: 99%

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Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

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The present work studied the role of the polar group unconjugated oxygen on the inhibition of positronium (Ps) formation in two binary blends made from a set of chosen constituent polymers with polar and weakly polar groups (nonpolar). The polymer blend samples of PVC-EVA and PVC-SAN were investigated by coincidence Doppler broadening and positron lifetime techniques. The strong polar acetate group in the EVA contributed to positron annihilation with electrons of unconjugated oxygen (-C + =O − ) as revealed by the momentum distribution curves peaking around 17 P L (10 −3 m 0 c). The ortho-Ps intensity indicated the unconjugated oxygen shows about a 28% Ps reduction even in the presence of a strong Ps inhibiting halogen (Cl − ). In contrast, this effect was not seen in the PVC-SAN blends since SAN contains a weakly polar (nonpolar) acrylonitrile group (C≡N). Our results indicate the chlorine of PVC in the blends is a major contributor to Ps inhibition through the formation of a (Cl − -e +) bound state but the unconjugated oxygen in EVA of the PVC-EVA blend also plays a similar, but lesser, role.

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Section: Positron Annihilation Lifetime Measurements (Pals)mentioning

confidence: 99%

Section: Positron Annihilation Lifetime Measurements (Pals)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

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“…The spectrometer consists of two BaF 2 scintillators and associated electronics. 44,45 A 17lCi 22 Na positron source deposited on pure kapton foil of thickness 12.5 mm and source-sample sandwich geometry was used to acquire lifetime spectrum with more than a million counts under each spectrum.…”

Section: Positron Annihilation Lifetime Measurementsmentioning

confidence: 99%

A new insight into interface widths in binary polymer blends based on ortho‐positronium lifetime studies

Ramya

Ranganathaiah

2012

J of Applied Polymer Sci

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The interface widths in two immiscible polymer blend (Poly vinyl chloride (PVC)/Polystyrene (PS)) and PVC/Ethylene Vinyl Acetate (EVA) are determined experimentally using hydrodynamic interaction approach through free volume measurement by positron annihilation lifetime spectroscopy. For comparison, the same study is performed in a miscible blend (Styrene Acrylonitrile (SAN)/Poly Methyl Methacrylate (PMMA)). The interfacial width (Dl) is evaluated from the hydrodynamic interaction (a) based on Kirkwood-Risemann theory and friction coefficient from Stokes equation. Friction at the interface of a binary blend evidences how close the surfaces of the polymer chains come or stay apart which in turn depends on the type of force/interaction at the interface. In this work, we define interface width from a different perspective of Flory-Huggins interaction approach. Measured composition dependent interface widths in the three blends studied clearly demonstrate the sensitivity of the present method. In miscible blend, high friction at the interface results in stronger hydrodynamic interaction and hence smaller interface widths (0.36-1.97 Å ), whereas weak or no interaction in immiscible blends produce wider widths (2.81-25.0 Å ).

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“…Source contribution and resolution functions were estimated from the lifetime of well-annealed aluminum using the program RESOLUTION. 15 A time resolution of 220 ps was obtained using three Gaussian resolution functions, which gave better convergence of the spectrum. More details on the instrumentation and spectrum analysis can be found elsewhere.…”

Section: Positron Lifetime Measurementsmentioning

confidence: 99%

Diffusion of seawater in unsaturated polyester resin and its glass fiber reinforced composites in the presence of titanium dioxide as UV absorber

Urs

Ranganathaiah

Ramani

et al. 2006

J of Applied Polymer Sci

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Diffusion of seawater in unsaturated polyester resin (UPR) and its glass fiber reinforced composite in the presence of titanium dioxide has been studied by sorption method. Incorporation of glass and TiO 2 to UPR alters the seawater diffusion process from Fickian to nonFickian type. The dual mode sorption model is used to separate Fickian-controlled and relaxation-controlled diffusion in case of UPR-T, UPR-G, and UPR-GT. The presence of TiO 2 seems to stabilize UPR and its glass reinforced samples but an increase in the rate of seawater diffusion is observed for these systems. The free volume determined from positron lifetime measurements support the diffusion data in these systems. Results further indicate that the contribution to diffusion in the later stages of sorption is due to the increased contribution from the interfaces. The plasticizing effect of TiO 2 is clearly seen even in the glass reinforced composite. DMA results show an increase in flexibility because of TiO 2 presence both in the neat as well as glass reinforced resin which is well supported by decrease in T g value from DSC data.

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Positron annihilation and differential scanning calorimetric study of poly(trimethylene terephthalate)/EPDM blends

Cited by 86 publications

References 23 publications

Influence of polar groups in binary polymer blends on positronium formation

Influence of polar groups in binary polymer blends on positronium formation

A new insight into interface widths in binary polymer blends based on ortho‐positronium lifetime studies

Diffusion of seawater in unsaturated polyester resin and its glass fiber reinforced composites in the presence of titanium dioxide as UV absorber

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