8 Nanocomposites Based on Thermosetting Polyurethane Matrix. . .
127
8.3.3 AFM Investigation of the Nanocomposites
In Fig. 8.2 the topography of the PU matrix is presented. The ordering of hard
(dark regions) and soft (light regions) segments of PU, i.e., microphase separation,
is exhibited. This is in agreement with the SAXS investigation of this matrix
(Fig. 8.1).
In Fig. 8.3 the phase images of PU nanocomposites with different loadings of
MWCNT-ox are presented. The MWCNT filler was not observed in the matrix,
but AFM images reveal changes in the structure of PU matrix induced by their
inclusion. For nanocomposites, containing 0.01% MWCNT-ox, the nanodomain
structure of polyurethane is preserved, and the hard and soft domain microphase
separation is observed (Fig. 8.3a, b). Increasing the MWCNT-ox content up to 0.1%
in the nanocomposites results in dramatic changes in the PU structure which exhibits
nearly complete disappearance of the hard and soft domains in the matrix structure
(Fig. 8.3c, d).
When increasing the amount of nanotubes up to 0.25 wt. %, the nanostructure of
polyurethane matrix is partly retained (Fig. 8.3e, f). Therein, the higher loading of
MWCNTs increases the possibility of re-agglomeration which, obviously, entails
poorer dispersibility (which can be observed when comparing TEM images in
Fig. 8.4). It is therefore surmised that some regions of PU are not penetrated by
MWCNTs at high filler contents, thus allowing polymerization with the restricted
influence of MWCNTs and the generation of hard and soft domains.
When small quantities of MWCNTs (0.01%) are used in the preparation of
nanocomposites, the number of nanotubes is insufficient to noticeably influence the
domain structure of PU. When increasing the amount of MWCNTs up to 0.1% and
a good dispersion of nanotubes, the effective surface of MWCNT-ox becomes large
enough to prevent the formation of hard and soft domains. At 0.25% MWCNTox (0.25%), part of nanofiller is present in agglomerates allowing the formation of
the soft and hard domains. Introduction of MWCNT-hemin changed the structure
of polyurethane less dramatically, but the change in the size of the hard and soft
Fig. 8.2 Tapping mode AFM
topography for pure PU
matrix. The size of square is
500 nm
127
8.3.3 AFM Investigation of the Nanocomposites
In Fig. 8.2 the topography of the PU matrix is presented. The ordering of hard
(dark regions) and soft (light regions) segments of PU, i.e., microphase separation,
is exhibited. This is in agreement with the SAXS investigation of this matrix
(Fig. 8.1).
In Fig. 8.3 the phase images of PU nanocomposites with different loadings of
MWCNT-ox are presented. The MWCNT filler was not observed in the matrix,
but AFM images reveal changes in the structure of PU matrix induced by their
inclusion. For nanocomposites, containing 0.01% MWCNT-ox, the nanodomain
structure of polyurethane is preserved, and the hard and soft domain microphase
separation is observed (Fig. 8.3a, b). Increasing the MWCNT-ox content up to 0.1%
in the nanocomposites results in dramatic changes in the PU structure which exhibits
nearly complete disappearance of the hard and soft domains in the matrix structure
(Fig. 8.3c, d).
When increasing the amount of nanotubes up to 0.25 wt. %, the nanostructure of
polyurethane matrix is partly retained (Fig. 8.3e, f). Therein, the higher loading of
MWCNTs increases the possibility of re-agglomeration which, obviously, entails
poorer dispersibility (which can be observed when comparing TEM images in
Fig. 8.4). It is therefore surmised that some regions of PU are not penetrated by
MWCNTs at high filler contents, thus allowing polymerization with the restricted
influence of MWCNTs and the generation of hard and soft domains.
When small quantities of MWCNTs (0.01%) are used in the preparation of
nanocomposites, the number of nanotubes is insufficient to noticeably influence the
domain structure of PU. When increasing the amount of MWCNTs up to 0.1% and
a good dispersion of nanotubes, the effective surface of MWCNT-ox becomes large
enough to prevent the formation of hard and soft domains. At 0.25% MWCNTox (0.25%), part of nanofiller is present in agglomerates allowing the formation of
the soft and hard domains. Introduction of MWCNT-hemin changed the structure
of polyurethane less dramatically, but the change in the size of the hard and soft
Fig. 8.2 Tapping mode AFM
topography for pure PU
matrix. The size of square is
500 nm