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Poster

Influence of molecular weight in the solubility,diffusivity and the subsequent cellular structure of polystyrene foams

Wednesday (24.10.2018)
19:33 - 19:36
Part of:
Line-Up:
- Poster Battery housings for electric vehicles using CFRP and aluminium foam 0 Joachim Baumeister
- Poster Manufacturing and characterization of open-cell stainless steel foams by investment casting 1 Jan Frömert
- Poster Interface formation of Mg2X (X = Si, Sn) in cellular Si infiltrated by Mg(Sn) alloys 1 Alexander M. Matz
- Poster Production of microcellular PMMA using the bead foaming technology 1 Mikel Mugica
- Poster Nanocellular PMMA with tunable cellular structure by changing the rheological behaviour of the polymer matrix. 1 Judith Martín de León
- Poster Production of thermoplastic polyurethane foams synthesized with different contents of hard segment and graphene nanoplatelets by the gas dissolution foaming process 1 Ph.D. Mercedes Santiago-Calvo
- Poster Surface functionalized filters for aluminum melt filtration 1 Dr.-Ing. Claudia Voigt
- Poster Nanocellular polymers based on PMMA/sepiolite nanocomposites: characterization of the mechanical behaviour 1 Victoria Bernardo
- Poster Impact resistant foams based on PP/POE blends 1 Ph.D. Santiago Munoz Pascual
- Poster Crosslinked open cell ethylene butyl acrylate copolymer (EBA) foams: properties and applications 1 Ph.D. Eduardo López
- Poster Influence of molecular weight in the solubility,diffusivity and the subsequent cellular structure of polystyrene foams 1 Ph.D. Alberto Ballesteros
- Poster Crushing strength measurement at reticulated ceramic foams ex situ and in situ CT analysis 1 Dr.-Ing. Claudia Voigt
- Poster Initiation of plateau region during compression test of porous metals with aligned unidirectional pores 1 Tomoya Tamai
- Poster Active meta-materials with adjustable pore size 1 Dr. Reza Hedayati
- Poster Polymeric foams 3D numerical mechanical modelling 1 Stefano Tagliabue
- Poster Characterisation of NiTi cellular materials fabricated by the powder-metallurgy spaceholder technique 1 Dr. Karl Dahm
- Poster Accurate separation of open cell metal foams using remote laser cutting technique 1 Robert Baumann
- Poster Generation of artificial foam structures and evaluation of their thermo-mechanical, flow and filtration characteristics (Poster) 1 Christoph Settgast
- Poster Surface modification of magnesium-based foams by Directed Plasma Nanosynthesis 1 Viviana Marcela Posada Pérez

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Molecular weight is defined as the average weight of the molecules that compose a polymer and is connected with the length of the polymeric chains. Several properties like glass transition temperature or some mechanical ones, such as stiffness, are affected by an increment in the molecular weight. In addition, viscosity of a molten polymer increases as molecular weight rises until it reaches a critical value. In industrial processes, the parameter used to correlate viscosity with molecular weight is the melt flow index. Viscosity is also a critical parameter during the foaming behavior of a polymer. However, the effect of molecular weight on the foaming behavior of polystyrene has not been previously studied. This paper is focused on this topic analyzing in detail how the modification of the molecular structure of the polymer strongly affects important properties of the material in foaming process such as solubility and diffusivity and the cellular structure of the foams produced.


In the present work, three types of polystyrenes with different melt flow indexes (that is, different molecular weights) have been used. The molecular weight of the three polymers has been estimated by using the Williams-Landel–Ferry and Arrhenius models in dynamic shear measurements. The glass transition temperature has been also evaluated by using differential scanning calorimetry (DSC). Finally, the relationship between the strain hardening coefficient and the molecular weight was obtained by extensional rheology measurements.


The foaming experiments were conducted using the gas dissolution foaming process with CO2 as blowing agent. The experimental conditions for saturation were 8 MPa and 40ºC. Solubility and diffusivity measurements were also conducted. Foaming tests were performed by heating the materials at 120ºC once they were removed from the pressure vessel. Foams with very low densities (around 30 kg/m3) were produced. Cellular structure parameters (cell size distribution, average cell size, cell density, anisotropy ratio and open cell content) were measured.


Results show that polymers with a higher value of the melt flow index and hence, a low molecular weight present a higher CO2 uptake. On the other hand, materials that present a higher value of the molecular weight showed a higher diffusivity after saturation. Finally, cellular materials produced with polymers with a low value of the molecular weight showed lower densities and lower cell sizes.

 

Speaker:
Ph.D. Alberto Ballesteros
University of Valladolid
Additional Authors:
  • Dr. Ester Laguna Gutierrez
    University of Valladolid
  • Prof. Dr. Miguel Ángel Rodríguez-Pérez
    University of Valladolid