Nano fibrillated cellulose (NFC) nanocomposite films were prepared with dispersed
monolayer clay nano platelets; films with 50% loading showed high transparency,
very high LOI values of *96.5%, and self-extinguishing ability [73]. Barrier formation is also important for FR activity, because it prevents heat and oxygen transfer,
thus inhibiting flame propagation. Clay addition to a polymer matrix drastically
improves its barrier properties by creating maze-like or tortuous paths that hinder gas
molecule diffusion through the polymer matrix. Thus, barrier formation mainly
depends on the interactions between the clay and polymer. Alonso et al. [74] prepared
PU/clay nanocomposites using different types of clays, including Cloisite
®
10A
(C10A), Cloisite
®
20A (C20A), and Cloisite
®
30B (C30B) and investigated the effect
of clay structure on the barrier properties and FR activity. The barrier properties
follow the order of C30B > C10A > C20A. C10A contains benzene rings in the clay
structure and polymer chains cannot penetrate the clay gallery, whereas C30B contains two hydroxyl groups of tallows, which help the penetration of polymer chains
into the clay gallery. They also form hydrogen bonds with the PU chains. Based on
the interactions between the organically modified clay and polymer, the formation of
clay nanocomposite structures is classified into three types, high-interactions exfoliation, low-interactions intercalation, and very low-interactions aggregation or
delamination. Kuruma et al. [75] prepared water-dispersible PU-clay nanocomposites
using two different organically modified clays and they observed three different clay
nanocomposite structures; the exfoliated structures showed a high improvement in the
composite properties.
Fig. 7.6 In-situ polymerization of P,N-containing PDEPD/clay nanocomposites [69]. Reproduced
with permission from Elsevier Science Ltd
7.2 Clay-Based Flame-Retardant Polymer Nanocomposites
95
monolayer clay nano platelets; films with 50% loading showed high transparency,
very high LOI values of *96.5%, and self-extinguishing ability [73]. Barrier formation is also important for FR activity, because it prevents heat and oxygen transfer,
thus inhibiting flame propagation. Clay addition to a polymer matrix drastically
improves its barrier properties by creating maze-like or tortuous paths that hinder gas
molecule diffusion through the polymer matrix. Thus, barrier formation mainly
depends on the interactions between the clay and polymer. Alonso et al. [74] prepared
PU/clay nanocomposites using different types of clays, including Cloisite
®
10A
(C10A), Cloisite
®
20A (C20A), and Cloisite
®
30B (C30B) and investigated the effect
of clay structure on the barrier properties and FR activity. The barrier properties
follow the order of C30B > C10A > C20A. C10A contains benzene rings in the clay
structure and polymer chains cannot penetrate the clay gallery, whereas C30B contains two hydroxyl groups of tallows, which help the penetration of polymer chains
into the clay gallery. They also form hydrogen bonds with the PU chains. Based on
the interactions between the organically modified clay and polymer, the formation of
clay nanocomposite structures is classified into three types, high-interactions exfoliation, low-interactions intercalation, and very low-interactions aggregation or
delamination. Kuruma et al. [75] prepared water-dispersible PU-clay nanocomposites
using two different organically modified clays and they observed three different clay
nanocomposite structures; the exfoliated structures showed a high improvement in the
composite properties.
Fig. 7.6 In-situ polymerization of P,N-containing PDEPD/clay nanocomposites [69]. Reproduced
with permission from Elsevier Science Ltd
7.2 Clay-Based Flame-Retardant Polymer Nanocomposites
95