Hemp Nanofibrils Reinforced Polycaprolactone Composites

Cellulose micro and nanofibrils were prepared from hemp fibers by means of a chemical/mechanical treatment and ultrasonication in water suspension. A sol-gel treatment with dimethyldiethoxysilane (MSDS) or titanium (IV) isopropoxide as precursors was developed to avoid the issue of the irreversible aggregation of the fibrils after drying (process known as "hornification"), which results in a material that is not suitable for composite applications. Polycaprolactone composites with 5% dried fibrils were compounded using a Mini extruder. The composites reinforced with cellulose fibrils showed an increase of the storage modulus (stiffness of the composite). Loss modulus (E'') also increased substantially with the addition of hemp fibrils. The reaction of silane on the surface of hemp fibrils prevented hornification in some extent, allowing an effective distribution of the cellulose fibrils in the polymer matrix