Structural and Nanomechanical Properties of Paperboard Coatings Studied by Peak Force Tapping Atomic Force Microscopy
ABSTRACT Paper coating formulations containing starch, latex, and clay were applied to paperboard and have been investigated by scanning electron microscopy and Peak Force tapping atomic force microscopy. A special focus has been on the measurement of the variation of the surface topography and surface material properties with a nanometer scaled spatial resolution. The effects of coating composition and drying conditions were investigated. It is concluded that the air-coating interface of the coating is dominated by close-packed latex particles embedded in a starch matrix and that the spatial distribution of the different components in the coating can be identified due to their variation in material properties. Drying the coating at an elevated temperature compared to room temperature changes the surface morphology and the surface material properties due to partial film formation of latex. However, it is evident that the chosen elevated drying temperature and exposure time is insufficient to ensure complete film formation of the latex which in an end application will be needed.
SourceAvailable from: Matteo Lorenzoni[Show abstract] [Hide abstract]
ABSTRACT: The nanomechanical properties of solvent cast polymer thin films have been investigated using PeakForce TM quantitative nanomechanical mapping. The samples consisted in films of polystyrene and poly(methyl methacrylate) obtained after dewetting of toluene solution on a polymeric brush layer. As a second step, we have probed the mechanical properties of Poly(styrene-n-methilmethacrylate) (PS-b-PMMA) block co-polymers (BCP) thin films randomly oriented. The measured films has a critical thickness below 50 nm and present features to be resolved of less than 42 nm. Measured surface elastic modulus obtained present a good agreement with previous literature and show how PeakForce technique could be crucial to BCP investigation predicting the mechanical stability of the different phases.Proc. SPIE 9423, Alternative Lithographic Technologies VII; 01/2015
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ABSTRACT: The presence and characteristics of a connected network of polyaniline (PANI) within a composite coating based on polyester acrylate (PEA) has been investigated. The bulk electrical conductivity of the composite was measured by impedance spectroscopy. It was found that the composite films containing PANI has an electrical conductivity level in the range of semiconductors (order of 10-3 Scm-1), which suggests the presence of a connected network of the conductive phase. The nanoscopic distribution of such a network within the cured film was characterized by Peak Force Tunneling Atomic Force Microscopy (AFM). This method simultaneously provides local information about surface topography and nanomechanical properties, together with electrical conductivity arising from conductive paths connecting the metallic substrate to the surface of the coating. The data demonstrates that a PEA-rich layer exists at the composite-air interface, which hinders the conductive phase to be fully detected at the surface layer. However, by exposing the internal structure of the composites using a microtome, much higher population of a conductive network of PANI, with higher elastic modulus than the PEA matrix, was observed and characterized. Local current-voltage (I-V) spectroscopy was utilized to investigate the conduction mechanism within the nanocomposite films, and revealed non-Ohmic characteristics of the conductive network.ACS Applied Materials & Interfaces 10/2014; 6(21). DOI:10.1021/am505161z · 5.90 Impact Factor
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ABSTRACT: In this study, three systems containing BMP-2 were fabricated, including two electrospun sandwich-like-systems of PLGA 75:25 and PLGA 50:50 and a microsphere system of PLGA 50:50 to be implanted in a critical size defect in rat calvaria. The in vivo BMP-2 release profiles of the three systems were similar. The total dose was released during the first two weeks. To evaluate the nano and microstructure of the regenerated bone a multi-technique analysis was used, including stereo microscope, X-Ray; AFM, micro-CT and histological analyses. The progression of bone regeneration was followed at 4, 8 and 12 weeks after the microsphere system implantation whereas the two electrospun systems were evaluated at fixed 12 weeks. All the techniques applied showed high bone regeneration. The average values of bone volume density, bone mineral density, Young's modulus and the percent of bone repair were approximately 70% of the values of the native bone. Besides, SEM-EDX analysis indicated that the main chemical elements in the new bone were oxygen, calcium and phosphorus in a ratio similar to that of native bone. In comparison, the micro-CT may provide an alternative to histology for the evaluation of bone formation at the defect size. This article is protected by copyright. All rights reserved. © 2015 Wiley Periodicals, Inc.Journal of Biomedical Materials Research Part A 02/2015; DOI:10.1002/jbm.a.35436 · 2.84 Impact Factor