Strong and Optically Transparent Films Prepared Using Cellulosic Solid Residue Recovered from Cellulose Nanocrystals Production Waste Stream

Abstract

We used a new cellulosic material, cellulosic solid residue (CSR), to produce cellulose nanofibrils (CNF) for potential high value applications. Cellulose nanofibrils (CNF) were produced from CSR recovered from the hydrolysates (waste stream) of acid hydrolysis of a bleached Eucalyptus kraft pulp (BEP) to produce nanocrystals (CNC). Acid hydrolysis greatly facilitated homogenization to fibrillate CSR to CNF with only 15 passes in a microfluidizer compared with at least 47 passes to fibrillate BEP to nanofibrils. CNF from CSR were nanowhiskers with a length between 50 and 400 nm and a diameter 3-10 nm with limited aggregation while CNF from BEP were entangled networks of nanofibrils with a length of 500-1000 nm and a diameter of 10-50 nm. CNFs from CSR had good spectral transparency from UV to infrared, i.e, transmittance of CNF-CSR suspensions at 0.1% solids consistency is greater than 90% at wavelengths greater than 340 nm, compared with less than 30% for CNF suspension produced from BEP. Specific tensile strength and modulus of CNF films from CSRs reached 75 kN·m/kg and 12 MN·m/kg, respectively, approximately 175% of the respective values for conventional paper made of refined BEP.

Effect of OPEFB-NCC Axial Ratio on Optical Properties of NCC Film

“…According to Nogi et al (2009) [11], the lack of transparency is caused by surface light scattering, hence if the porosity between the fibres are small enough to avoid light scattering the nanocellulose film will become transparent while maintaining the high performance of the material. It has also been reported in various studies [14]- [16] that the optical properties of nanocellulose film vary widely depending on the properties of the cellulosic material and preparation conditions of the nanocellulose films.…”

“…An important parameter for NCCs is the geometrical axial ratio, which is defined as the length-towidth ratio [13], and is a major factor that controls the properties of NCC based material [6], [8] that nanocellulose films that are produced from high axial ratio nanocellulose fibres from wood and softwood appear to be translucent with high porosity [11], [14]- [16] and to obtain higher transparency nanocellulose the film surface are smoothen with several modification process including use of hot pressed [11], [15] and polishing or laminating using transparent resin [11]. According to Nogi et al (2009) [11], the lack of transparency is caused by surface light scattering, hence if the porosity between the fibres are small enough to avoid light scattering the nanocellulose film will become transparent while maintaining the high performance of the material.…”

Controlling the Size and Film Strength of Individualized Cellulose Nanofibrils Prepared by Combined Enzymatic Pretreatment and High Pressure Microfluidization

“…Cellulose nanofibrils (CNFs) are suitable raw materials for novel functional materials because of their excellent physical and mechanical properties (Klemm et al 2011;Moon et al 2011;Wang et al 2013). Functional materials including fiber, films, membranes, aerogels, scaffolds, and hybrid composites have been developed from CNFs Tang et al 2015).…”

“…Functional materials including fiber, films, membranes, aerogels, scaffolds, and hybrid composites have been developed from CNFs Tang et al 2015). CNFs are usually isolated by mechanical fibrillation using a homogenizer (Pääkkö et al 2007;Spence et al 2011), microfluidizer (Wang et al 2013), or ultra-fine friction grinder (Wang et al 2012a). The liberation of CNFs by physical pretreatment of untreated cellulosic materials requires a lot of energy, i.e., 10 to 40 kWh/kg (Spence, et al 2011;Wang and Zhu 2015).…”

“…Previously, individualized CNFs were produced from residual cellulose recovered from the waste stream of acid hydrolysis (Wang et al 2013). This acid treatment was hydrolytic and decreased the fiber length and degree of polymerization.…”