Fabrication and characterization of nanofibrillated cellulose and its aerogels from natural pine needles.

To obtain the nanofibriled cellulose from natural pine needles, a combination of chemical pretreatments and subsequently ultrasonic treatments was employed for removing the hemicelluloses and lignins and splitting the bundled cellulose into pine needle nanofibers. Using SEM and diameter distribution method, it was confirmed that the obtained pine needle nanofibers had a narrow diameter from 30 to 70 nm. The crystalline type of the pine needle nanofibers was the cellulose I type. The crystallinity reached 66.19%, which was increased by 7.61% as compared with the raw material pine needles. The TGA and DTG results showed that the degradation temperature of the nanofibers was increased to approximately 267 and 352°C compared with 221 and 343°C of the raw material fibers, respectively. Furthermore, the highly flexible and ultralight pine needle nanofibers aerogels were prepared from the aqueous pine needle nanofibers solution using the freezing-drying technique. Aerogels were studied by SEM observation and nitrogen gas adsorption. The mechanical properties were measured in compression for aerogels. This study provides a new opportunity to fabricate novel nanomaterials from waste biomass materials, which is crucial for the fully utilizing of abundant biomass resources.