Mechanical and barrier properties of spray dried carboxymethyl cellulose (CMC) film from bleached bagasse pulp

Abstract

In this work, the spherical shape of carboxymethyl cellulose (CMC) tiny particles with high purity was successfully produced. Carboxymethyl cellulose from bleached bagasse pulp (CMCB) was synthesized at various alkaline concentrations from 20%(w/v) to 60%(w/v) and then the spray drying process was utilized as a simultaneous shape forming and purification step to obtain CMC microspheres without remnants of cellulose fibers. The alkalization of the bleached bagasse cellulose for carboxymethylation had no significant effect on the degree of substitution (DS), which was approximately 0.80. Increasing alkaline concentration influenced the properties of the CMC microsphere; e.g. increasing%NaCl and resulted to degrade cellulose fiber as observed by the gradual decreasing of%yield, %CMC, density, crystallinity and particle size. The morphology of CMCB microspheres revealed more crack marks on the surface and their granule sizes were smaller (0.10–0.15μm) when adding 40–60% (w/v) NaOH concentrations. The CMCB spray dried microspheres were cast to CMC films and their physical, mechanical and barrier properties were further investigated to determine the proper alkaline concentration for mercerization step. The CMCB film of microphere using 40%(w/v) NaOH showed the highest tensile strength (53.7MPa) as well elongation at a break of 3.09%. Increasing alkaline concentration coupled with the use of the spray drying process resulted in decreasing film viscosity but increasing CMCB film’s water solubility, tensile strength and elongation (up to 40%, w/v of NaOH concentration), water vapor and oxygen gas transmission rates (WVTR and OTR). The WVTR and OTR of CMCB film were reported to be in the range of 14.25–16.76g/m2day and 1.94–5.50×10−4cm3/m2dayPa, respectively. This led to a development of a high CMCB film value.