Partially exfoliated nanocomposites

Figure M Calculated nanocomposite phase diagram (in the limit of small organoclay loadings). Solid line is the phase boundary between weakly intercalated stacks and partially exfoliated, partially intercalated phase, as calculated using compressible SCFT. Dashed line is the phase boundary between immiscible and exfoliated phases, as calculated by incompressible SCFT.

Intercalated and partially exfoliated PVC-clay nanocomposites were produced by melt blending in the presence and absence of DOP and characterised by X-ray diffraction and transmission electron microscopy. The effects of various factors, including volume fraction of clay, plasticiser content, melt compounding time and annealing, on nanocomposite structure and the thermal and mechanical properties of the nanocomposites were also examined. It was found that the best mechanical properties were achieved at 2% clay loading and 5 to 10% DOP loading. 18 refs. 

However, in addition to this, there is evidence of improvements found with partial exfoliation [102, 103] of tactoids formed by 10-20 lamellas, due to required flexibility of the dispersed particles. Interfacial interactions are of fundamental importance in the structure and properties of nanocomposites. Lee et al. [104] proposed that the interactions of the polar maleic groups grafted to PP with hydroxyl groups of... 

TPV nanocomposites of LLDPE/reclaimed rubber with nanoclay and 1 wt.% MA-grafted PE and curative were prepared using a Brabender internal mixer at 170°C (Razmjooei et al., 2012). Contents of the reclaimed rubber, nanoclay, and compatibilizer were varied up to 30, 7, and 21 wt.%, respectively. The blends without the compatibilizer were also prepared. Morphological, thermal, and mechanical properties of the nanoclay-reinforced TPV nanocomposites indicated intercalation and partial exfoliation by the high-shear stress during mixing with the reclaimed rubber. Vulcanization of rubber phase led to an increase of viscosity. The size of rubber particles in TPV was reduced with the addition of nanoclay and compatibilizer. 

Mesua ferrea L. seed oil-based highly thermostable and biodegradable polyester/clay nanocomposites exhibited 2.6- and 6-fold improvement in tensile strength and elongation at break, respectively, and about a 150°C increase in thermostability under the influence of a nanoclay loading of 5 wt%. The formation of well-dispersed partially exfoliated... 

Epoxy-modified Mesua ferrea L. seed oil-based polyurethane/clay nanocomposites at different loadings (1-5 wt%) have been studied as biocompatible biomaterials. The partially exfoliated nanocomposites were prepared by an ex situ solution technique under high mechanical shearing and adequate ultrasonication at room temperature. The nanocomposites exhibited enhanced mechanical properties such as tensile strength (twofold) and scratch hardness (five-fold), thermostability (to about 40°C), and an increase in the rate of biodegradation between five- and ten-fold. All the nanocomposites showed RBC haemolysis inhibition observed by anti-hemolytic assay carried out on the sterilised films. 

Bisphenol-A-based epoxy with a poly(amido amine) hardener system cured Mesuaferrea L. seed oil-based hyperbranched polyurethane (HBPU)/ clay nanocomposites obtained by an ex situ solution technique, was also reported. The partially exfoliated nanocomposites showed a two-fold improvement in adhesive strength and scratch hardness, 10 MPa increments in tensile strength and thermostability at 112°C with little effect on impact resistance, bending and elongation at break compared to a pristine epoxy-modified HBPU system. However, similar epoxy-cured Mesua ferrea L. seed oil-based HBPU/clay nanocomposites exhibited a two-fold increase in tensile strength, a 6°C increase in melting point and thermostability at 111°C after nanocomposite formation using an in situ technique. An excellent shape recovery of about 96-99% was observed for the nanocomposites. The above observations confirm that the performance characteristics of nanocomposites are influenced by their preparation technique. 

Organoclay/functionalised triglycerides, such as acrylated ESO, maleini-sed acrylated ESO and soybean oil pentaery thritol maleates, combined with styrene-based partially exfoliated nanocomposites were prepared. The... 

The ultimate clay nanocomposite is formed when individual clay plates are completely dispersed into a polymer matrix. This type of composite yields the maximum improvement in properties. This complete dispersion is normally referred to as full exfoliation. In many cases the composites reported in the literature are intercalated or partially exfoliated. Intercalated systems are characterized by insertion of polymer between plates of clay with retention of well-defined spacing distance between the plates. This spacing is called the gallery spacing and is determined... 

The co-continuous structure and the final rheological properties of an immiscible polymer blend are generally controlled by not only the viscoelastic and interfacial properties of the constituent polymers but also by the processing parameters. For example, the effect of plasticizer on co-continuity development in blends based on polypropylene and ethylene-propylene-diene-terpolymer (PP/EPDM), at various compositions, was studied using solvent extraction. The results showed more rapid percolation of the elastomeric component in the presence of plasticizer. However, the same fuUy co-continuous composition range was maintained, as for the non-plasticized counterparts (Shahbikian et al. 2011). It was also shown that the presence of nanoclay narrows the co-continuity composition range for non-plasticized thermoplastic elastomeric materials (TPEs) based on polypropylene and ethylene-propylene-diene-terpolymer and influences their symmetry. This effect was more pronounced in intercalated nanocomposites than in partially exfoliated nanocomposites with improved clay dispersion. It seems that the smaller, well-dispersed particles interfere less with thermoplastic phase continuity (Mirzadeh et al. 2010). A blend of polyamide 6 (PA6) and a co-polyester of... 

D-B transition temperature, and the effect of elastomer MFI on the D-B transitirMi temperature becomes less prominent with the increased PP molecular weight as seen in Fig. 17.18. The nanocomposites based on the high-octene-content elastomer ( 39 wt%) also lead to a lower D-B transition temperature compared with nanocomposites based on the elastomer with low octene content ( 28 wt%). The toughening mechanism was not explored for this system a more detailed study in this area would further enhance the understanding of the role of organoclay in elastomer-toughened nanocomposites with partially exfoliated clay particles. 

The extent of nanofiller dispersion and matrix properties have a significant effect on the overall blend properties, for example, highly exfoliated MMT particles in the polyamide matrix can make it brittle, whereas partially exfoliated clay particles in extruder-made thermoplastic olefin nanocomposites can lead to significant improvements in impact strength depending on the PP molecular weight and elastomer MFI. 

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