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44. Film Formation and Foamability of Cellulose Derivatives: Influence of Co-binders and Substrate Properties on Coating Holdout.

Author

Lyytikäinen, Johanna, Ovaska, Sami-Seppo, Heiskanen, Isto, and Backfolk, Kaj

Abstract

Foams were prepared from hydrophobically modified ethyl(hydroxyethyl) cellulose (EHEC), methyl nanocellulose, and native microfibrillated cellulose (MFC). Their film- and foam-forming abilities, stabilities, and suitabilities for foam coating on different substrates were investigated. The role of EHEC as a polymeric stabilizing agent was also studied. The EHEC-MFC foams showed greater stability and water-holding ability under pressurized dewatering than MFC foams prepared in the presence of a surfactant. A foam could be created with methyl nanocellulose without any foaming agent. Selected nanocellulose gels and foam formulations were used to coat various substrates. The surface was efficiently closed by gel and foam coatings prepared from the methyl nanocellulose and EHEC solutions, which was ascribed to good coating holdout. Coatings on papers with different levels of smoothness/density and hydrophobicity/ hydrophilicity confirmed that foam-substrate interactions affected the coat quality. The air permeance was reduced by 99% and 64% with a methyl nanocellulose coating and an EHEC-MFC coating, respectively. An EHEC-MFC coating created a hydrophobic surface on a hydrophilic substrate, and methyl nanocellulose improved the oil resistance even at a low coat weight. [ABSTRACT FROM AUTHOR]

Published
2021
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50. Thermal analysis and topographical characterization of latex films by scanning probe microscopy.

Author

Ihalainen, Petri, Backfolk, Kaj, Sirviö, Petri, and Peltonen, Jouko

Subjects
*SCANNING probe microscopy, *LATEX, *TEMPERATURE, *POLYMERS, *SURFACE roughness
Abstract

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 surface sensitivity and more localized effects than the other approach. Furthermore, the progress of the latex film formation and the effect of the different drying conditions on film topography were studied by SPM imaging and roughness analysis. Skewness and local surface curvature are demonstrated to serve as useful numerical measures with which to distinguish different levels of particle deformation and the formation of a continuous film. Preannealing of the samples at high temperature influenced not only the topography (roughness) but also the characteristics of the thermal transitions. [ABSTRACT FROM AUTHOR]

Published
2007
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