PROCESSING AND CHARACTERIZATION OF MICRO AND NANOCELLULOSE FIBRES PRODUCED BY A LAB VALLEY BEATER (LVB) AND A SUPER MASSCOLLOIDER (SMC)

Abstract

Cellulose nanofibers, known for their high aspect ratio (>150), are difficult to process and characterize due to a variety of reasons, including lower diameters. In this work, cellulose micro and nanofibers produced by a Lab Valley Beater (LVB) and a Super Masscolloider (SMC) were characterized using optical microscopy and SEM. The thermal degradation behavior was analyzed using thermogravimetric analysis and solar radiation tests. With decreasing clearance between two grinders, SMC refining resulted in fibres with smaller diameter (400 nm to 8 μm) and a marginal increase in the number of fines was noted. LVB refining resulted in fibres with shorter length (500 μm), but a significant increase in the number of fines, contributing to higher tensile strength. The tensile strength of SMC sheets was 10-fold lower and severe ductile fracture was observed when compared to LVB refining. However, a 30 °C increase in thermal stability was found for fibres produced by SMC compared to LVB refining. This could be due to lesser heterogeneity in fibre morphology (reduced packing density), lack of surface fibrillation (reduced mechanical interlocking) and altered cellulose-lignin interaction for SMC refined fibres. Hence, it can be recommended to use blends of LVB and SMC refined fibres to make sheets for applications involving higher temperatures (250 °C) and higher tensile strengths (25 MPa), but the sheets need to be fabricated using the cast evaporation technique by maintaining the water bath temperature at 95-98 °C. The dust capturing ability of SMC sheets was tested using a dust sampler and it was found that sheet SMC_0.01 can capture PM2.5 dust particles, i.e. a weight increase of 7% was noticed in 6 h.