Polycarbonate matrix blends

The degradation and combustion behavior of polycarbonate/POSS hybrid system has been reported recently.48 Different loading contents of trisilanolphenyl-POSS (TPOSS) were melt blended with polycarbonate matrix (PC). The data shown in Table 8.4 indicate that no improvement in thermal stability parameters (i.e., onset decomposition temperature and peak decomposition temperature) was observed compared to the neat polycarbonate. The thermo-oxidative degradation process of the hybrid system proved to be a complicated process, which includes hydrolysis/alcoholysis of the carbonate linkage, free radical oxidative chain degradation, reformation, and branching and cross-linking reactions. 

The above systems are fairly simple, homogeneous systems since they contain only one polymer in the matrix. Blending polymers makes the behavior more complex. In polypropylene/polycarbonate blends, carbon black is preferentially located in the polycarbonate phase. A blend which is better mixed is less conductive than a blend in which carbon black predominantly resides in the polycarbonate phase where it can form a conductive network. These are properties which control morphology (and related electric conductivity) ... 

As an example, the tensile deformation of polycarbonate/polyethylene blends is similar for a range of concentrations except for the magnitude of the yield stresses (Yee 1977). In this blend polycarbonate matrix undergoes strong yield shearing, and the decisive factor is the shear resistance of polycarbonate. 

As Carfagna et al. [61] suggested, the addition of a mesophasic polymer to an amorphous matrix can lead to different results depending on the properties of the liquid crystalline polymer and its amount. If a small amount of the filler compatible with the matrix is added, only plasticization effect can be expected and the dimensional stability of the blend would be reduced. Addition of PET-PHB60 to polycarbonate reduced the dimensionality of the composite, i.e., it increased the shrinkage [42]. This behavior was ascribed to the very low... 

However, in that survey Schein and Tyutnev question the intermolecular origin of cr. They compared cr values derived from studies of hole transport in 1-phenyl-3-((diethylamino)styryl)-5-(p-(diethylamino)phenyl)pyrazoline (DEASP) molecules, derivatives of pyrazoline, whose dipole moment is 4.34 D, blended with either polystyrene or polycarbonate as function of concentration. They found that cr is independent of the matrix material and that a remains constant when the concentration of DEASP increases from 10% to 70% while one would expect that cr increases as... 

Kolarik J, Lednicky F, Locati G, Fambri L (1997) Ultimate properties of polycarbonate blends effects of inclusion plastic deformation and of matrix phase continuity. Polym Eng Sd 37 128-137... 

REDOR was also applied to examine the structure and dynamics of interfaces of heterogeneous polymer blends. A heterogeneous blend was prepared from [carbonyl- C]polycarbonate and poly(p-fluorostyren-co-styrene) copolymer of p-fluorostylene. The blend was formed by coprecipitation from chloroform into methanol. A fluorine dephased REDOR signal indicates that the 1 polycarbonate chain in 20 exists at the interface, suggesting that the polycarbonate phase is embedded in a continuous polystyrene matrix which is 200 A thick or 400 A in diameter [54],... 

The Bjorklund works [169] lead us to develop a synthesis route in which the polypyrrole grows in the insulating matrix. Different solutions (PVC, polycarbonate, polyphenylene oxide,. ..) or emulsions (PTFE) of insulating polymer have been tested. In the case of PTFE-polypyrrole blend we used a classical oxidising coupling process by FeCl3 [104,127]. Comparative experiments have been performed on granular materials obtained by polypyrrole powder dispersion in an elastomer or an epoxyde resin [127]. 

The physical mixing of two or more polymers to crate a material with properties different from each of the components has become an increasingly popular route to new materials development. The resulting blend or alloy greatly reduces the associated time and costs while permitting improved processibility and enhanced properties tailored to specific application areas. Many commercial examples of two-phase polyblends consist of a matrix polymer impact modified by the addition of rubber particles. Recently, however, TLCPs have received increasing attention in the scientific and technical literature as in situ reinforcements in polymer blends and microcomposites. The matrices examined in the literature include polyimides, PES, PEI, PEEK, polycarbonate, PET, PPS, and polyarylate. 

A reason for blending PBT with PC is to overcome the comparatively poor solvent resistance of polycarbonate. The enhanced solvent resistance of the blend would be expected if PBT was the continuous matrix phase in the blend, as suggested by Hobbs et al [46-47]. However, the observation that the d.c. conductivity of polycarbonate and its blends is orders of magnitude less than that of PBT and PET over a substantial temperature range indicates unambiguously that the PC-rich phase forms the continuous matrix in each of the blends investigated here. It would seem that the enhanced solvent resistance in PC/PBT blends can only arise from the substantial proportion of evenly-distributed PBT which is contained in the matrix. 

For impact-modified PC/PBT and PC/PET blends evidence has been presented for partial miscibility of the component polymers and for a two-phase blend morphology with a polyester-rich dispersed phase in a continuous matrix rich in polycarbonate. Other absorptions are attributed respectively to MWS interfacial polarization, to the presence of the impact modifier and to a phosphite processing stabilizer. 

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