Robert J. Moon

Processing and Characterization of Cellulose Nanocrystals/Polylactic Acid Nanocomposite Films

The focus of this study is to examine the effect of cellulose nanocrystals (CNC) on the properties of polylactic acid (PLA) films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization behavior, thermo-mechanical behavior, and mechanical behavior were determined as a function of CNC content using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis, and tensile testing. Film crystallinity increases with increasing CNC content indicating CNC act as nucleating agents, promoting crystallization. Furthermore, the addition of CNC increased the film storage modulus and slightly broadened the glass transition region.

Influence of high loading of cellulose nanocrystals in polyacrylonitrile composite films

Polyacrylonitrile-co-methacrylic acid (PAN-co-MAA) and cellulose nanocrystal (CNC) composite films were produced with up to 40 wt% CNC loading through the solution casting method. The rheological properties of the solution/suspensions and the structural, optical, thermal, and mechanical properties of the resulting films were investigated. The viscosity of the composite suspensions increased with higher CNC loadings and with longer aging times. PAN-co-MAA/CNC films maintained a similar level of optical transparency even with up to 40 wt% CNC loading. The glass transition temperature (Tg) increased from 92 to 118xa0°C, and the composites had higher thermal stability below 350xa0°C compared to both neat PAN-co-MAA and neat CNC. The mechanical properties also increased with higher CNC loadings, elastic modulus increased from 2.2 to 3.7xa0GPa, tensile strength increased from 75 to 132xa0MPa, and the storage modulus increased from 3.9 to 10.5xa0GPa. Using the Kelly and Tyson model the interfacial shear strength between the PAN-co-MAA and CNC was calculated to be 27xa0MPa.

Post-sulfonation of cellulose nanofibrils with a one-step reaction to improve dispersibility

Cellulose nanofibrils (CNF) were sulfonated and the dispersion quality was compared to unfunctionalized and 2,2,6,6-tetramethylpiperdine-1-oxyl radical (TEMPO) post-oxidation treatment of existing CNF (mechanically fibrillated pulp). A post-sulfonation treatment on existing CNF in chlorosulfonic acid and dimethylformamide (DMF) resulted in sulfonated CNF that retained a fibril-like morphology. There was a small decrease in the cellulose crystallinity index for the sulfonated CNF, but this was much lower than the reported regioselective oxidative bisulfite pretreatment method used to make sulfonated CNF. The current approach was extremely quick, and 5min of reaction time was sufficient to result in significant improvements in dispersibility compared to unfunctionalized CNF. The sulfonated CNF and TEMPO oxidized CNF had better dispersibility compared to the unfunctionalized CNF when dispersed in DMF and water, and in many cases the sulfonated CNF had better dispersibility than the TEMPO CNF. It was found that when CNF was dispersed in DMF the TEMPO CNF formed carboxyl dimethylammonium groups, while the sulfonated CNF formed formate groups.

Comparative Study of Lightweight Glass Fiber and Basalt Fiber Sheet Molding Compound (SMC) Composites Containing Cellulose Nanocrystals

Cellulose nanocrystals are used in lightweight sheet molding compound composites made with either glass fiber (GF)/epoxy or basalt fiber (BF)/epoxy. The chosen approach for making lightweight SMC composites is replacing portion of the heavier components, i.e. GF or BF, with a small amount of CNC with the constrain that there is no compromise on mechanical performance. The specific properties of the lightweight composites containing CNC are compared with those of corresponding composites with no CNC to investigate the effectiveness of using CNC for light weighting for each type of micro-size reinforcement, i.e. GF and BF. We report that incorporation of 1.4-2 wt% CNC in the epoxy matrix can allow for reduction of the GF from 60 wt% to 44-48 wt% resulting in ~11 % lighter composites with no penalty on specific tensile, flexural and impact properties. In contrast, for the case of BF, addition of CNC does not increase the properties of the light weighted composites to the level of BF/epoxy with 60 wt% fiber content.