Civil Engineering Reference
In-Depth Information
obtained results were compared with the extrusion/injection-molded samples. h e
extrusion process caused CNW agglomeration and resulted in reduced properties
compared to the composite samples prepared using solution casting [52]. Ten
et al.
[53] have reported the processing of PHBV/CNW nanocomposites by solution casting
using polyethylene glycol (PEG) as a compatibilizer between i ber and matrix, con-
i rming the nucleating ef ect of cellulose nanowhiskers and their positive impact on
mechanical properties [53]. Ef ects of CNW on dif erent properties of PHBV, such as
dielectric and rheology, have been recently reported by Ten
et al.
[54] . h e agglom-
eration of cellulose nanowhiskers in PHBV/CNW is rel ected in the reduction of real
permittivity. In addition, the rheological analysis of PHBV/CNW composites exhibits
a reduced glass transition temperature due to the possibility of PHBV-CNW network
formation without geometrical overlapping [54].
9.2.1.3
Poly(lactic acid) (PLA)-Based Nanocomposites
Polylactide or poly(lactic acid), otherwise known as PLA, is biodegradable thermo-
plastic polyester that is manufactured by biotechnological processes from renewable
resources (e.g., corn). Although other sources of biomass can be used, corn has the
advantage of providing the required high-purity lactic acid. h e use of alternative start-
ing materials (e.g., woody biomass) is being pursued in order to reduce process costs;
however, the number of steps involved in deriving pure lactic acid from such raw mate-
rials means that their use remains much less cost ef ective at present. Cellulose-based
nanostructures have been utilized for improving PLAs.
Iwatake
et al.
[55] have reported the reinforcement of polylactic acid (PLA) using
microi brillated cellulose (MFC, mechanically i brillated pulp, mostly consisting of
nanoi bers). h e study was carried out to know the potential of reinforcement by a
nanoi ber network, with the goal of making sustainable "green-composites." h e MFC
was premixed with PLA using organic solvent and the mixture was needed to attain
uniform dispersion of MFC in PLA. h e production procedure to attain uniform dis-
persion of MFC in a PLA compound was assessed, and then mechanical and thermo-
mechanical properties of the sheets at er hot-pressing of the compounds were studied.
Needle-leaf bleached krat pulp (NBKP) and rei ner-treated NBKP were also used to
study the ef ects of i ller morphology. h e MFC increased Young's modulus and tensile
strength of PLA by 40% and 25%, respectively, without a reduction of yield strain at
a i ber content of 10 wt%. On the other hand, NBKP reduced the yield strain by 30%
and reduced the strength by 15% at a i ber content of 5 wt%. h e uniformly dispersed
MFC reinforcement increased the Young's modulus and tensile strength of PLA by 40%
and 25%, respectively, without a reduction of yield strain at a i ber content of 10 wt%.
Furthermore, the storage modulus of the composites was kept constant above glass
transition temperature of matrix polymer. MFC is a promising reinforcement of PLA
composites.
Fortunati
et al.
[56] studied PLA/nanocellulose nanocomposite i lms prepared by
twin-screw extrusion followed by a i lm formation process. Cellulose nanocrystals were
synthesized from cellulose microcrystals by sulphuric acid hydrolysis. h e crystal sur-
face was modii ed with surfactant (acid phosphate ester of ethoxylated nonylphenol) as
a means to improve the dispersion of i ller in PLA matrix. h e presence of surfactant
