(165j) Influence of Surface Modification on the Micro- and Nano-Scale Dynamics of a Cellulose Nanocrystal Nanocomposite

The use of cellulose nanocrystals (CNCs) has seen an increase in interest for numerous industrial applications due to their low cost, high abundance, and lightweight features. Due to the extremely hydrophilic nature of CNCs, the number of matrices that the particle can be dispersed in is limited. Therefore, functionalizing the surface groups of the crystal is necessary in to increase its hydrophobicity and allow for dispersion in commonly used hydrophobic polymer matrices. Following the modification of the particle, it also critical to understand how the microstructure of the composite changes during post-processing. In-situ cure monitoring can reveal vital information regarding the microstructure properties of the composites, which is directly related to the overall performance of the composite (tensile strength).

In this work, we explore the dynamics of a surface-functionalized CNC during the curing in a commonly used thermosetting resin (EPON 828). X-ray photon correlation spectroscopy (XPCS), coupled with differential scanning calorimetry (DSC), reveal drastic changes in the dynamics and curing kinetics of the composite as a function surface modification. To confirm that the crystals were successfully functionalized, both Fourier transform infrared, and x-ray diffraction was utilized to verify results before dispersing the crystals in the hydrophobic thermosetting epoxy resin. Two levels of modification (7 & 10 %) were chosen to perform observations at a constant loading of 5 wt%. The goal of this study is to compare the macroscale curing dynamics using DSC to non-isothermally cure with the microscale dynamics using XPCS. By using XPCS to compliment the macroscale results obtained from DSC, it is possible to fully understand the preliminary and final dynamics displayed by the composite on a microscale level that cannot be observed using simply DSC. With the results we’ve obtained using both methods, the degree of cure using either an isothermal or non-isothermal procedure can be better understood, and techniques can be tailored to achieve desired properties.