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Nanoscopic properties of silica filled polydimethylsiloxane by means of positron annihilation lifetime spectroscopy

Författare

  • Petra Winberg
  • Morten Eldrup
  • Frans Maurer

Summary, in English

Positron annihilation lifetime spectroscopy (PALS) was performed on a series of polydimethylsiloxane (PDMS)/fumed silicon dioxide (SiO2) composites at temperatures between -185 and 100degreesC to study the effect of filler content and filler particle size on the free volume properties and the positron annihilation characteristics. The glass transition behavior of the PDMS/SiO2 composites was determined with differential scanning calorimetry. A clear influence on the o-Ps lifetime (73) in the polymer upon addition of nano-sized fumed SiO2 was observed at all temperatures. The observed o-Ps lifetime behavior was related to filler content and filler particle size. A transition in the temperature dependence of the o-Ps lifetime was observed close to -35degreesC above which temperature PDMS exhibits long o-Ps lifetimes. A relationship between tau(3) and the surface tension, equivalent to the behavior of ordinary molecular liquids was observed in this temperature region. The o-Ps yield was strongly reduced in the crystallization region and by addition Of SiO2. The reduction due to filler addition did, however, in the case of nano-sized SiO2 not follow a linear relationship with filler weight, which was observed for micron-sized fillers. The nonlinear relationship between filler weight and o-Ps yield could be due to out-diffusion of positrons and/or o-Ps from the filler particles to the matrix. (C) 2004 Elsevier Ltd. All rights reserved.

Publiceringsår

2004

Språk

Engelska

Sidor

8253-8264

Publikation/Tidskrift/Serie

Polymer

Volym

45

Issue

24

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Chemical Sciences

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0032-3861