Papers by Author: Juha Sarlin

Abstract: Due to its high purity, favourable surface chemistry and huge specific surface area, fumed silica nanoparticlesare suitable inorganic nanoscopic templates for organic modification and nanocomposite studies. Polypropylene offers good properties with low or moderate cost for many technical applications, such as for solid dielectrics. Polypropylene and hydrophilic silica nanoparticles have inherently dissimilar surface chemistries and organic modification of the silica is usually needed to achieve good mixing and nanocomposite properties. Thetarget is to study robust grafting methods which can be up-scalable without complicated process steps. In thiswork nanosilica particleshave been modified by grafting to method using equimolar amounts of various chain lengths of vinyl functional polyisobutene (PIB) oligomers (molecular weights 320 g/mol, 920 g/mol and 2300 g/mol, determined by material supplier), further functionalized by epoxidation and subsequent reaction with organosilane.The glass transition temperature, viscoelastic properties and crystallization behaviour of the PP compositeswith PIB grafted silicas (4.5 wt% silica) were altered. Especially the PIB2300 grafted silica composite showed improved low temperature fracture toughness, significantly (14°C) lower glass transition measured by DMA and higher crystallization temperature compared to the pure polypropylene.

Abstract: The properties of polymeric materials have been enhanced by developing nanocomposites in several projects at the Technical Research Centre of Finland VTT. The improvement of conductivity, dielectric, mechanical properties and the thermal stability of polymer materials opens new application potential in electronic industry. In this paper the results of several projects are presented. By applying nano-POSS particles in polypropylene and epoxy the break down voltage was increased by 10 - 20%. The use of carbon nanotubes in polyaniline enhanced the conductivity by two decades compared to the commercially available polymers.