Material properties of nanofiller-reinforced polymer composites are governed by various phenomena such as stress transfer, fracture, thermal diffusion, and light scattering etc., which occur at the interface between nanofillers and polymer matrix. Thus, it is important for composite materials to control the interfacial structure. In the present study, contributions of the interfacial thickness and the interfacial density to the composite properties were investigated using TEMPO-oxidized cellulose nanofiber (TOCN) and cellulose triacetate (CTA). To control the interfacial thickness, the surfaces of TOCNs were modified by grafting amine-terminated poly(ethylene glycol) (PEG-NH2) with different molecular weight. Neat TOCN or PEG-grafted TOCN was compounded with CTA to prepare the nanocomposite films with different interfacial thicknesses. As a result, the thinner interfaces enhanced stiffness of the nanocomposite films, while the thicker interfaces enhanced toughness. In the neat TOCN/CTA composite films, a rigid network of TOCNs was formed and contributed to the increase in Young’s modulus and tensile strength. In contrast, in the case of PEG-grafted TOCN/CTA composite films, the network of TOCNs was loosened by the soft PEG layer, which is responsible for the increase in toughness. The soft and thick PEG layer on the TOCN surface is likely to show large deformation and thus prevent brittle fracture at the interface. High light transmittances and a low haze value of CTA films were preserved even with the addition of neat TOCN or PEG-grafted TOCN. This result can arise from the small width and high dispersibility of the TOCNs. The coefficient of thermal expansion (CTE) of CTA films decreased by incorporating neat TOCN or PEG-grafted TOCN. The CTE of the composites with the thicker interface was higher than that of the composites with the thinner interface. In fact, PEG-NH2/CTA composite films had higher CTE than PEG-grafted TOCN/CTA composite films which consist the corresponding amount of PEG. Therefore, the PEG layer on the TOCN surfaces had a negative impact on the restraint of thermal expansion of the composites. These results show that an appropriate thickness of the interface is required to efficiently improve material properties of the composites.

Interfacial thickness for tailoring the reinforcing properties of nanocellulose in polymer matrix

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.