TY - JOUR A1 - Dreßler, Martin A1 - Nofz, Marianne A1 - Pauli, Jutta A1 - Jäger, Christian T1 - Influence of polyvinylpyrrolidone (PVP) on alumina sols prepared by a modified Yoldas procedure JF - Journal of sol gel science and technology N2 - Al13 polycations containing alumina sols, prepared by a modified Yoldas procedure were mixed with polyvinylpyrrolidone (PVP). Although Al speciation in freshly prepared sols was not affected by PVP addition the decay rate of Al13 polycations was slightly decreased in PVP-containing sols. PVP does not show any influence on particle size and particle growth. The influence of PVP addition on viscosity and flow behavior of modified Yoldas sols depends on their solids content and NO3-/Al molar ratio. KW - ModifiedYoldas sols KW - PVP KW - NMR KW - Rheology KW - Particle size KW - Aging PY - 2008 DO - https://doi.org/10.1007/s10971-008-1798-9 SN - 0928-0707 SN - 1573-4846 VL - 47 IS - 3 SP - 260 EP - 267 PB - Kluwer Academic Publ. CY - Dordrecht AN - OPUS4-17854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Munz, Martin T1 - Evidence for a three-zone interphase with complex elastic-plastic behaviour - nanoindentation study of an epoxy/thermoplastic composite JF - Journal of physics D N2 - A detailed study of the mechanical interphase (IP) between an amine-cured epoxy and the amorphous thermoplastic polyvinylpyrrolidone (PVP) was performed. The amine curing agent was diaminodiphenylsulphone (DDS). With 170 °C, the curing temperature was close to the glass transition temperature of PVP. Using a depth-sensing indentation setup equipped with a Berkovich indenter, force penetration curves were measured at different positions on the cross-section of an epoxy/PVP/epoxy sandwich specimen. Profiles of the sample Young's modulus, Es, the hardness, H, and the plasticity index, ψ, were analysed as a function of the distance from the epoxy/PVP interface. Each of these quantities showed significant variations. Furthermore, the profile of the ratio between the reduced modulus of the tip–sample contact, Er, and the hardness is shown to reflect the profile of the plasticity index, that is the relative amount of plastic indentation work. A relationship is presented that allows the calculation of the plasticity index from the ratios Er/H and hf/hc, where hf and hc denote the final depth and the contact depth, respectively. Although the Young's modulus shows strong variations, the hardness appears to be the most sensitive parameter for IP property variations. Three different zones can be identified from the hardness profile, with respective widths of ~21.3, 52.5 and 160.9 µm, which add up to a total IP width of ~234.7 µm. Zone Z1 is located next to the PVP layer. The outer edge of zone Z2 is located at a position similar to the one of the amine depletion zone. The latter was detected by means of energy-dispersive analysis of x-rays and its width is ~71 µm. Inspection of the residual imprints shows a larger plastic deformation for zone Z1, in agreement with the high values of the plasticity index and of the creep deformations. From these grounds, the different IP zones are discussed in terms of the diffusion processes taking place during the epoxy curing procedure. Zone Z1 is associated with bi-directional interdiffusion across the initial interface. Zone Z3 can be attributed to long-ranging effects reaching far beyond the amine depletion zone. KW - Interphase KW - Epoxy/thermoplastic composite KW - PVP KW - DDS KW - AFM KW - EDX KW - Polymer interdiffusion PY - 2006 DO - https://doi.org/10.1088/0022-3727/39/18/016 SN - 0022-3727 SN - 1361-6463 VL - 39 IS - 18 SP - 4044 EP - 4058 PB - IOP Publ. CY - Bristol AN - OPUS4-13134 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -