Compatibilizer interlayers

Reactive interfacial agents formed compatibilizer interlayers around nanosize magnesium hydroxide and CNT. 

The general influence of a compatibilizer on the crystallization behavior of an immiscible polymer blend system is stiU far from being well understood. However, abstract can be made between two main classes. A first class consists of compatibilizers that form a kind of immiscible interlayer between the two phases. Examples are given by Holsti-Miettinen et al. [1992], and... 

FA-g-EBA +GMA-g-E EA 80/20 60/40 —> depending on type of compatibilizer . cryst. around. retarded cryst. (AT= 50°C) PP dispersed 40% no large shift down of => no lack of nuclei in droplets => If SEES, EBA or E EA => immiscible interlayer between phases => small droplets with lack of nuclei=> T 4-4 c PP droplets are large (coalescence) and contain enough heterogeneities to cryst. at [Ikkala et al, 1993]... 

MAH-g-PP +FA-g-EBA +GMA-g-EEA 80/20 60/40 of binary blend and MAH-g-PP PA-6 dispersed coincident crystallization with PP SEES, EBA and E EA form immiscible interlayer between PA-6 and PP => no nucleation =>T =T c,PP c,bulk Compatibilization => serious reduction of PA-6 droplet size => lack of nucleating species => retarded cryst. [Ikkala et al, 1993]... 

In consequence, the flow imposed morphologies can be classified as (i) Dispersion (mechanical compatibilization), (ii) Fibrillation, (iii) Lamellae formation, (iv) Coalescence, (v) Interlayer slip, (vi) Encapsulation, etc. These types will be discussed below under appropriate headings. 

The rheological consequences of these changes can be predicted from a model system. The emulsion model indicates that making the interface more rigid causes the intrinsic viscosity of the emulsion to increase (see Eq 7.50). Similarly, an increase of the apparent volume of the dispersed phase causes the relative viscosity to increase (see Eqs 7.24-7.25). Furthermore, enhanced interactions between the phases will reduce the possibility of the interlayer slip, and increase formation of associative network formation, which may result in the yield stress. In short, compatibilization is expected to increase melt viscosity, elasticity and the yield stress. 

The compatibilizer as such may be compatible with the clay surfaces and hence easily intercalates into the interlayer spacing of the clay platelets and separates the clay platelets, and with bulk polymer it leads to the formation of well-dispersed nanocomposites. The compatibilizer widely used for polypropylene (PP) is maleic anhydride grafted PP (PP-g-MA) [15-16], Other compatibilizers used are diethyl maleate (DEM-g-PP) and polyolefin elastomer grafted maleic anhydride (POE-g-MA),... 

The clay remains as microtactoids (dispersed in microlevels) when it is dispersed in PP without the assistance of compatibilizer. By adding maleic anhydride grafted PP (PP-g-MA) as compatibilizer, well dispersed clay platelets are observed in the PP matrix. When polyolefin elastomer grafted maleic anhydride (POE-g-MA) compatibilizer is used, even two-phase separation has been reported between PP and POE-g-PP [15]. This phase separation is not identified in TEM analysis and it confirms the compatibility of clay and POE-g-PP. POE-g-PP enters into interlayer spacing and facilitates the delamination of clay layers. 

As mentioned above, the copolymers or nonionic surfactants (or compatibilizers) like PP-g-MA or PE-g-MA are used to achieve better compatibility between the polar clay interlayers and apolar polyolefins matrices [34-44]. Figure 1.4 demonstrates the schematic of compounding of PP with the organically modified montmorillonite in the presence of PP-g-MA. It has been observed in almost all the reported studies that the filler... 

In ternary nanocomposites, compatibilizers have been mostly used to improve the adhesion at the polymer/filler interface rather than to modify the polymer/elastomer interface. Mishra et al. [80] compounded PP/EPDM/organoclay (75/25/5 wt%) and added PP-g-MA (1 wt% MA) as a compatibilizer with a clay/PP- -MA ratio of 1/3. They characterized the interlayer spacing of the clay platelets by XRD and observed that it increased from 3.4 to 4.3 nm for systems without and with compatibilizer. This was attributed to a better diffusion of the PP-g-MA chains inside the interlayer spacing thanks to their functional groups. Numerous other authors prepared and characterized ternary composites with a compatibilizer. Examples include Lim et al. [81] and Lee et al. [5] on PP/PP- -MA/POE/ organoclay systems, Mehta et al. [23] on PP/PP-g-MA/EPR/organoclay systems, and Liu and Kontopoulou [24,45] on PP/PP-g-MA/ethylene-octene copolymer/silica composites. It should be noted that the compatibilizer itself may affect the properties of the matrix... 

Similar results were found when a polypropylene-block-poly(propylene glycol), PP-b-PPG, diblock copolymer was utilized as compatibilizer its ability to increase the interlayer distance of PP/dimethyl dioctadecyl ammonium-modified montmorilonite hybrids was studied and compared with the corresponding behavior of PP-g-MA [55]. The ratio of compatibilizer to organoclay used was low but nevertheless 2 wt% of PP-b-PPG resulted in a 4A increase of interlayer distance, which was better than what was observed utilizing maleated PP under the same conditions. 

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