Master curves of the storage modulus G0 of PMMA/cMAM blends
as a function of frequency at 210 C are shown in Fig. 5. Neat PMMA
shows the classical behaviour of a thermoplastic polymer melt with
a terminal relaxation zone at low frequencies. Rheological behav-
iours of PMMA/cMAM blends differ from PMMA at low frequencies
as they show drastic modification of the terminal relaxation zone.
This variation increases with the increasing copolymer content and
appears to be more important in the case of PMMA/CoreeShell
MAM blends (see Fig. 5b), with the appearance of a secondary
plateau at low frequencies for a copolymer content of 20 wt%.
This behaviour has been studied for many thermoplastic poly-
mers/rubber particles systems and attributed to a network-type
structure formed by the soft nodules [29,30]. It was found to
depend on rubber volume fraction and on rubber nodule size.
Moreover, the appearance of stronger interaction between the
particles [31] also leads thermoplastic polymers containing rubber
particles to exhibit a low frequency plateau, for nodule contents
higher than 15 wt% [29]. The variation in the absolute complex
viscosity jh*j with angular frequency also highlights this modifi-
cation of the terminal relaxation zone (see Fig. 6).
In the case of PMMA, the Newtonian plateau viscosity is reached
and the zero shear viscosity could be estimated at 2.5 104 Pa s.
The increase in copolymer content in blends leads to higher com-
plex viscosities at low frequencies, away from Newtonian plateau
(yield stress rheological behaviour) values and can be intensified in
the case of PMMA/CoreeShell MAM materials.