TY - JOUR A1 - Cappella, Brunero A1 - Stark, Wolfgang T1 - Adhesion of amorphous polymers as a function of temperature probed with AFM force-distance curves N2 - Force–displacement curves have been obtained with a commercial atomic force microscope at different temperatures and probe rates on a thick film of poly(n-butyl methacrylate) and on two films of polystyrene with different molecular weight. In a previous publication [B. Cappella, S.K. Kaliappan, H. Sturm, Macromolecules 38 (2005)1874] the analysis of force–displacement curves has been focused on the stiffness and on the Young's modulus of the samples. In the present publication we consider the temperature dependence of the work of adhesion. We have obtained master curves of the work of adhesion at fixed maximum loads and, by comparing the results of the two analysis, we show that the work of adhesion follows the Williams–Landel–Ferry equation with the same coefficients previously found for the Young's modulus. Furthermore, we show that the temperature dependence of the work of adhesion of the polymers is a consequence of the temperature dependence of the tip–sample contact area and in the end of the temperature dependence of the stiffness and of the elastic–plastic properties of the samples. KW - Atomic force microscope KW - Force-distance curves KW - Indentation KW - Elastic-plastic properties KW - Adhesion KW - Time-temperature superposition principle KW - Glass transition temperature PY - 2005 DO - https://doi.org/10.1016/j.jcis.2005.09.043 SN - 0021-9797 SN - 1095-7103 SP - 1 EP - 8(?) PB - Elsevier CY - Orlando, Fla. AN - OPUS4-11187 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Stark, Wolfgang A1 - Kelm, Jürgen A1 - Pashkov, V.M. A1 - Yakimenko, Y. T1 - Characterization of carbon black filled rubber compounds by the Microwave Coaxial Method KW - Dielectric parameters KW - Microwave methods KW - Filled rubber compounds KW - Vulcanisation PY - 2005 SN - 0025-5300 VL - 47 IS - 3 SP - 118 EP - 122 PB - Carl Hanser Verlag CY - München AN - OPUS4-7273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Straet, T. A1 - Bayerl, H. A1 - Stark, Wolfgang A1 - Döring, Joachim A1 - Kürten, Ch. T1 - Ultrasonic Measurements on Thermoset Moulding Compounds KW - Ultraschall KW - Fertigungskontrolle KW - Schallgeschwindigkeit KW - Vernetzungsreaktion KW - Qualitätssicherung PY - 2005 SN - 0945-0084 VL - 95 IS - 7 SP - 1 EP - 5 PB - Hanser CY - München AN - OPUS4-10304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Munz, Martin A1 - Sturm, Heinz A1 - Stark, Wolfgang T1 - Mechanical gradient interphase by interdiffusion and antiplasticisation effect - study of an epoxy/thermoplastic system N2 - A stoichiometric amine–epoxy formulation was cured in the presence of a thermoplastic, namely poly(vinylpyrrolidone) (PVP). The epoxy system consisted of the resin diglycidyl ether of bisphenol A (DGEBA) and the aromatic curing agent 4,4'-diaminodiphenylsulfone (DDS). As shown for this system in a former study by Oyama et al. [Oyama HT, Lesko JJ, Wightman JP. J Polym Sci B 1997;35:331–46. [36]], preferential absorption of amine molecules by PVP can occur. In the present study, the focus is on the variations of local elastic properties within the epoxy interphase adjacent to the PVP layer. The curing was performed close to the glass transition temperature, Tα, of the PVP film, namely at 170 °C. Variations of the local amine concentration were tracked using energy-dispersive analysis of X-rays (EDX), by taking benefit of the sulfur contained in DDS. Using temperature-dependent dynamic mechanical analysis (DMA), a series of epoxy reference samples of different amine–epoxy concentration ratios, r, was investigated in order to work out the relationship between r and the epoxy storage modulus at room temperature. In the excess-epoxy regime, r<1, the modulus is observed to increase with departure from the stoichiometric ratio, r=1. Considering the respective suppression of the ß-transition, the observed characteristic can be explained by an antiplasticisation effect. Depth-sensing indentation (DSI) experiments across the epoxy/PVP interphase provided evidence for strong modulus variations. In consistency with the EDX and the DMA data, in the vicinity of the PVP layer the local epoxy modulus is increased. The total change of the epoxy Young's modulus is ~1.1 GPa. However, the total width of the modulus decay of ~175 µm is ~2.5 times larger than the one of the DDS concentration gradient. This finding is discussed in terms of additional spatial variations of the DGEBA concentration as well as long-range diffusion currents of DDS induced by the interdiffusion processes and their effect on the final network of crosslinks. KW - Interdiffusion KW - Interphase/interface KW - Polymer PY - 2005 DO - https://doi.org/10.1016/j.polymer.2005.06.098 SN - 0032-3861 SN - 1873-2291 VL - 46 IS - 21 SP - 9097 EP - 9112 PB - Springer CY - Berlin AN - OPUS4-10893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -