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The mechanical properties of coating layers are critical for post-application processes such as calendering, printing, and folding. Discrete element methods (DEM) have been used to simulate basic deformations such as tensile and compression, but have not been used as a tool to predict cracking-at-the-fold (CAF) or picking. DEM has the potential to increase our understanding of these failure mechanisms at the particle level. We propose a method to model the three-point bending of a coating layer and also the out-of-plane picking event during printing (using a z-direction scenario and an approach involving a moving force/velocity). Properties of the binder and the binder concentration are input parameters for the simulation. The model predicts the crack formation of the layer, the flexural modulus, and the maximum flexural strain during bending. The model also predicts the forces required for picking to occur. Results are compared with those of complimentary studies. [ABSTRACT FROM AUTHOR]

Constantly growing interest in nanocellulose usage and applications is pushing the scientific community to search for suitable production and processing techniques. One example is use of nanocellulose as a barrier material in packaging applications, which requires processing of nanocellulose into films and coatings. It is challenging to coat nanocellulose suspensions using conventional pigment coating techniques due to their yield stress behavior and very high viscosity, even at low solids concentration. This work demonstrates a novel roll-to-roll coating method of nanocellulose on paperboard using slot die geometry. The rheology of nanocellulose suspensions in pressure-driven flow is found to play a critical role in enabling their coating using the said process. In this work, the slot die is used in an unconventional manner where the shearing and metering elements are combined to aid wet film formation and application of nanocellulose suspension onto the paperboard. Barrier performance of the nanocellulose coated paperboards against air, water, heptane vapor, grease, and oils was found to be reasonable and warrants further research on the subject. [ABSTRACT FROM AUTHOR]

Cellulose nanofibrils (CNF) were spun into filaments directly from suspension without the aid of solvents. The influence of starting material properties and drying temperature on the properties of filaments produced from three different CNF suspensions was studied. Refiner-produced CNF was ground using a microgrinder at grinding times of 50 and 100 minutes. Filament spinning was performed using a syringe pump-heat gun setting at three drying temperatures of 210 °C, 320 °C and 430 °C. The structure of starting CNF materials was first evaluated using a combination of optical and atomic force microscopy (AFM) techniques. Surface free energy analysis and attenuated total reflectance--Fourier transform infrared spectroscopy (ATR-FTIR) were used to study changes in hydrophobicity due to grinding. Morphology of the filaments was studied using SEM micrographs. The influence of different drying temperatures and grinding times on mechanical properties of the CNF filaments were further investigated through tensile tests and results were compared using statistical analysis. It was observed that drying temperature did not significantly influence the tensile properties of the filaments while cellulose nanofiber suspension type (grinding time) had a significant influence and improved mechanical properties. FTIR results confirmed an increase in crystallinity index and decrease in hydroxyl group availability due to grinding. [ABSTRACT FROM AUTHOR]

Melt rheology and crystallization behavior of polyamide 6 (PA 6) and microcrystalline cellulose (MCC) composites were systematically studied in this research. The incorporation of MCC into the PA 6 matrix resulted in higher complex viscosities (| η*|), storage modulus ( G′), and shear viscosities than those of neat PA 6, especially at low frequencies. The orientation of rigid molecular chains in the composites introduced by the addition of MCC induced a strong shear thinning behavior with an increase in MCC loading. The non-isothermal crystallization kinetics of PA 6 and MCC composites were investigated by differential scanning calorimetry. The Avrami and Tobin model were applied to describe the process of non-isothermal crystallization and to determine the crystallization parameters of the composites. Analysis of the crystallization kinetics indicated that the Avrami ( na) and Tobin exponent ( nt) was altered by the MCC. It was also found that the Avrami and Tobin equations fit the empirical data well. POLYM. ENG. SCI., 54:739-746, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The article focuses on the use of confocal laser scanning microscope in the three-dimensional observation of coated paper. The three-dimensional structure of a paper coating layer is observed through a laser beam which scans a specimen and a photodetector which collects the fluorescent light emitted. The results of the process can be used to characterize the depth of the coating layer penetration into the base paper, the occurrence of bubbles, and the possible distribution of latex and optical brightener.