Lignin, the second most abundant natural polymer on earth after cellulose, contains both hydrophilic and hydrophobic groups. In this study, the use of nanocellulose fibrils with high lignin content (NCFHL) has been explored to make polylactic acid (PLA) biocomposites with excellent mechanical, thermal, and barrier properties. Different amounts of NCFHL aqueous suspensions (5−20 wt %) were wet mixed with PLA latex to form composite films by casting and hot pressing. The presence of lignin imparted a strong compatibility between NCFHL and the PLA matrix, which overcame the major issue of poor interfacial bonding associated with nanocellulose fibrils without lignin previously reported by literature studies. Atomic force microscope infrared spectroscopy (AFM-IR) characterization results showed an effective coupling between NCFHL and PLA at the nanoscale. With 5−10 wt % of NCFHL additions to the PLA matrix, a significant improvement in mechanical, thermal, and water vapor barrier properties was observed for the resulting biocomposites. The addition of 10 wt % of the NCFHL increased the modulus and strength by 88% and 111%, respectively, and the water vapor transmission rate was reduced by 52%, compared to neat PLA.
In this work, the use of microsized
cellulosic particles obtained
from spray dried cellulose nanofibrils with high lignin content (>20
wt %) were explored for the first time as reinforcement in polypropylene
(PP) composites. Their effect was compared with the results from PP
composites reinforced by cellulosic particles of spray dried cellulose
nanofibrils with a low lignin content (<5 wt %). Cellulose nanofibrils
with diameters less than 100 nm were obtained by mechanically fibrillating
unbleached and bleached cellulosic fibers obtained from tree bark
after alkaline extraction for removal of extractive. These cellulose
nanofibrils were then spray dried to microsized high lignin content
cellulose particles (HLCP) and low lignin content cellulose particles
(LLCP), respectively. The presence of a large amount of lignin in
the nanofibrils alleviated the degree of aggregation during the spray
drying process. Both HLCP and LLCP were melt compounded with polypropylene
(PP) to make composites films with different cellulosic particle loading
levels. Compared to LLCP, HLCP significantly improved water repellency,
thermal stability, and tensile properties of the composites films.
With an addition of 5 wt % HLCP in PP, the tensile strength and modulus
of the composites increased by 25.3% and 41.5% compared to neat PP,
respectively. However, composites containing 5 wt % LLCP experienced
a decrease in tensile strength by nearly 23.0% instead. Moreover,
compatibilizing and stabilizing effects of lignin were also observed
during the processing of the composites. This study demonstrated strong
potential of HLCP as biobased reinforcement filler in plastic composites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.