Novel surface functionalization of cellulose fibers with polyurethane prepolymers in fiber cement composites: Impact on final properties and potential benefits for the production process

Abstract

The objective of this research was to perform a deep exploration of cellulose polyurethane (PU) fibers used in fiber cement boards for usage in building applications. Grafting treatment was performed on cellulose fibers with PU-pre-polymers, through a synthesis method using propylene carbonate solvent medium, followed by a cleaning step. Fiber cement boards were prepared thorough cement and limestone dispersion followed by a dewatering process, to roughly mimic the Hatschek production process. The experiments confirmed that grafted cellulose fibers can present lower water absorption (∼10 %) and greater fiber preservation, when embedded in alkaline matrix. Although the mechanical performance of fiber cement composites prepared with cellulose-PU fibers were not appreciably different, superior ability to drain water from the green cement sheet was demonstrated, which can provide great benefits during the production process. It’s worth mentioning that cellulose fiber is added in the air cured fiber cement formulation as a process aid agent to retain fine aggregates, and mechanical reinforcement is mainly carried out by the synthetic fibers. From the fiber cement production perspective, the reduced water retention showed in the green sheet can be beneficial in different production processes, e.g. the Hatschek or flow-on, in two ways: First, by possibly reducing the number of stops, as a lighter green sheet would be less prone to drop from the machine, and second, due to lower vacuum applied, possibly avoiding segregation and producing more homogeneous boards.