Cellulose
nanomaterials have attracted a great deal of interest
as sustainable alternatives to nonrenewable or fossil fuel-derived
materials, particularly in composite applications. Cellulose nanofibrils
(CNF) are most often derived from wood sources through energy-intensive
and costly mechanical fibrillation processes. In this study, recycled
cardboard, referred to as old corrugated cardboard (OCC), was investigated
as an alternate CNF source. OCC is a recycled material that can be
obtained at one-tenth the cost of the commonly used bleached softwood
Kraft pulp and can be refined to similar levels with nearly one-half
of the energy consumption. Additionally, the distinct composition
and morphology of OCC-derived CNF provides a more favorable fiber–matrix
interface and better reinforcement capabilities of the cellulose nanofibrils
in polymer matrices, displaying an over 70% increase in tensile modulus
at a loading of 40 wt % with no decrease in tensile strength. When
paired with biobased poly(l-lactide) (PLLA), OCC-derived
CNF is proven to be an attractive low-cost and low-energy reinforcing
agent for sustainable, high performance nanocomposites.