Silane modified cellulose nanocrystals and nanocomposites with LLDPE prepared by melt processing

Cellulose nanocrystals (CNCs) were surface modified with 3-isocyanatopropyl triethoxysilane (ICPTS) in tetrahydrofuran at 62-63 degrees C using triethylamine as a catalyst. ICPTS modified CNCs were further studied as a nanofiller in nanocomposites with linear low-density poly(ethylene) (LLDPE) prepared by melt processing. The modification of CNCs was confirmed by FTIR, solid state NMR, and thermogravimetric analysis. Compared to unmodified CNCs, the ICPTS modified CNCs show enhanced compatibility with LLDPE as shown by SEM. Nanocomposites processed at 70 degrees C reveal slightly enhanced mechanical properties and this effect was further intensified by increasing the molding temperature up to 120 degrees C. Under such conditions, a 20% increase in Young's modulus and 30% increase in tensile strength are achieved compared to neat LLDPE. Differential scanning calorimetry confirms the degree of LLDPE crystallinity, beside the CNC reinforcing network formation, as an important decisive factor in defining the final mechanical properties of LLDPE/CNC nanocomposites. The maximal enhancement of mechanical properties was observed at rather low amount of added ICPTS modified CNC (1-2 wt.%), which is important for practical application as CNCs are still rather expensive nanofiller. By modification of CNC with ICPTS the CNC polarity is reduced, which result in their improved compatibility with LLDPE, while on the other hand they function as a plasticizer and thus reduce the LLDPE crystallization degree, especially at high CNC concentrations. [GRAPHICS] .