Anchored metallocene linear low-density polyethene cellulose nanocrystal composites

Cellulose nanocrystals (CNCs) were functionalized with different loadings of metallocene catalyst and subjected to in situ polymerization with ethene and 1-hexene to yield linear low-density polyethene (LLDPE) polymer matrix composites (PMCs). CNC content was determined with thermogravimetric analysis, confirming that the PMCs varied in their CNC loadings from 3.6 to 11.4 wt%. Differential scanning calorimetric, gel permeation chromatographic and NMR spectroscopic analyses revealed that the LLDPE (matrix) components of these PMCs shared similar physical properties. Dynamic mechanical analysis showed a general increase in the storage modulus of the PMCs with increasing CNC content. These relative differences in storage modulus were even more evident at higher temperatures. Uniaxial tensile testing of the PMCs found a notable increase in Young's modulus between the 3.6 wt% CNC PMC (240 +/- 50 MPa) and the 11.4 wt% CNC PMC (391 +/- 7 MPa), while the elongation at break decreased from the 3.6 wt% CNC PMC (400 +/- 90%) to the 11.4 wt% CNC PMC (70 +/- 10%). All PMCs showed similar yield strengths of ca 10 MPa. These mechanical properties showed that the method of dispersing CNCs in LLDPE reported herein affords the highest moduli reported thus far in LLDPE-CNC PMCs. The ability of the catalyst to incorporate co-monomer olefins may allow for the incorporation of smart CNCs into ethane-based polymers. (c) 2020 Society of Industrial Chemistry