Synthesis and chemical modification of crystalline nanocellulose to reinforce natural rubber composites

Potential of crystalline nanocellulose (CNC), as green reinforcing filler, has been evaluated for the preparation of natural rubber (NR) composites. CNC is derived from a natural source (ramie fiber) and its surface is modified with different organosilanes to strengthen the rubber-filler interaction at the interface. It is found that, although at 2.5 phr (parts per hundred parts of rubber) loading of CNC the mechanical property of the NR composites is improved, it deteriorates at 5 phr loading. Surface modification of CNC by organosilanes is found very useful to overcome this issue. The modulus values at low strain become almost 1.5 to 2 times higher while tensile strength becomes 2.5 times higher for the modified CNC filled composites relative to those of CNC filled composites at 5 phr loading. These results are corroborated with a morphological study, where a very good state of dispersion of CNC particles is found in the surface-modified CNC filled composites. Moreover, the particle size of CNC becomes almost half, in respect to that of unmodified CNC particles, upon surface modification by organosilane. The reinforcement effect delivered by CNC and surface-modified CNC is also reflected by a small positive shift in Glass Transition Temperature (Tg) in differential scanning calorimetry study.