Petri Sirviö

Thermal analysis and topographical characterization of latex films by scanning probe microscopy

Scanning probe microscopy (SPM) was utilized to study the thermal behavior of latex films dried under different conditions. Using the SPM probe resonance frequency method, the resonance frequency (ω) of the oscillating probe above the sample surface was followed as a function of temperature (T). Two different approaches for detecting thermal transitions were used and compared. In the heating-by-the-sample approach, the SPM probe acts as a thermal sensor detecting the heat dissipated by the heated sample. In the heating-by-the-probe approach, the SPM probe is utilized simultaneously as an actuator and a sensor: the heated probe both dissipates heat and detects the heat reflected from the sample surface. Thermal transitions in the polymer films could be observed in the Δω-T curves. The results were consistent with those observed by differential scanning calorimetry, but also additional information about the characteristics of the transitions was obtained. The heating-by-the-probe method showed higher surfac...

X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper

A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 μm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate was strongly perturbed by protruding fibers of the base paper. Such fibers together with the surface topography of the base paper seem to be the major factors that control the leveling of toner and its penetration into a thinly coated paper substrate.