Page 280 - Biodegradable Polyesters

258 10 Highly Toughened Polylactide-Based Materials through Melt-Blending Techniques

partners, strengthening the interfacial adhesion between both partners and
therefore the material performance. Unlike copolymer-based compatibilizers,
nanoparticles are nonreactive, aspecific to the nature of immiscible polymer
blends, and readily incorporated on blending, providing a universal platform to
control the phase morphology and related material performances. Undoubtedly,
the potential use of nanoadditives in tailoring the morphology of various polymer
blends can have several advantages such as enhancing material properties with
an optimal stiffness/toughness balance, ease of processing, and lower cost in
comparison to copolymer-based compatibilizers [158].
In an attempt to achieve balanced overall properties, PLA ternary composites
containing both soft elastomer and rigid filler are of increasing interest to
industry and academia because they exhibit complementary rubber toughening
and nanoparticle reinforcement characteristics. Recently, a novel toughened PLA
bio-nanocomposite with tunable properties has been successfully prepared by
®
melt-blending PLA with natural rubber (NR) and organoclays (Cloisite 15A
®
and Cloisite 30B) [159]. From this investigation, it appeared that organoclays
acted as compatibilizers for the PLA/NR blend because of their preferential
location at the polymer interface, acting as a solid barrier and preventing the
coalescence of NR droplets. This location resulted in a marked improvement
of the physical and mechanical properties of the system upon the addition
of 1 wt% of Cloisite ® 15A within the PLA/NR (90/10 wt/wt%) binary blend.
Similar coalescence suppression upon the addition of organoclays within the
toughened PLA/linear low-density polyethylene (LLDPE) (90/10 wt/wt%) blends
were reported by Balakrishnan et al. [160]. As a result, smaller LLDPE droplets
were reached within the PLA-based nanocomposites and ultimately, promoted
balanced stiffness–toughness performances. Balance in the overall properties
was also achieved by As’habi et al. through the investigation of PLA/LLDPE
®
nanocomposites based on two commercially available nanoclays, Cloisite 15A
®
and Cloisite 30B [161–163]. From this study, it was found that the mixing
sequence has a remarkable influence on dispersion and localization of the
major part of nanoclay in the PLA matrix. However, partly exfoliated clay
platelets remained dominantly located at the interface between PLA and LLDPE,

1 μm 500 nm 100 nm
Figure 10.17 Morphologies of compatibilized PLA/LLDPE (25 wt%) nanocomposites con-
taining 4.5 wt% of Cloisite ® 30B. Reproduced with permission from Ref. [162]. © 2013,
Express polymer.