Dr. Martinho Machado Junior, Associate Professor, Universidade Federal da Fronteira Sul, BR 158, km 405, POBox 106, Laranjeiras do Sul-PR, Brazil

Biography: Graduate in Physics from the Federal University of Santa Catarina (1998), where he won the Summa Cum Laude. He is received his Master and PhD degree in Chemical Engineering from Department from the Chemical Engineering at Federal University of Santa Catarina in 2009 and 2015, respectively. He is currently Associate Professor of Mathematics at Federal University of Southern Frontier, Campus Laranjeiras do Sul / PR. Recently, he has been developing research in the polymers characterization with atomic force microscopy, tribological characterization of cellulosic structures in nanoscale from kraft paper used in packaging, papermaking and applied mathematics. He is member of a research group entitled “Food processing and by-products utilization” for food packaging development.

Speech Title: Friction Forces in Cellulose Fibers
Abstract: Friction is an important parameter for quality control of papers surfaces. It influences the movement of paper in industrial machines, printers, and prevents sliding of paper sheets in shipping. Their origins in paper are still obscure and difficult to understand once cellulosic structures with sizes ranging from micro- to nanoscale may have different contributions to the friction forces. Micron sized fibers, randomly oriented in paper surfaces may contribute to friction via fiber interlocking, while cellulosic structures may contribute to friction via intermolecular interactions. To better understand the contribution of friction forces of intermolecular nature and of mechanical locking we have measured the friction forces in cellulose fibers using a friction force microscope. Our results shows that the friction between the microscope tip and cellulose fibers and fibrils can be attributed to intermolecular interaction observed at point contacts on-top of macro- and microfibrils, and mechanical tip tripping at extended contact at the lateral of the cellulose fibers. The friction forces at the top of the cellulose fibrils were observed to be much smaller than friction due to tripping at the lateral of the fibers. The latter is comparable to friction forces measured in macroscale and interfiber experiments suggesting that tripping and fiber interlocking is one of the main physical mechanisms responsible for the friction forces during the relative motion of paper sheets.
Keywords: Cellulose; Fibers; Fibrils; Friction; Atomic Force Microscopy.