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Sodium-montmorillonite (MMT) was modified with two types of AP-POSS and
OA-POSS and dual-surfactants (POSS with a ditallow-based second surfactant:
04AP-POSS/08DTDMA and 04OA-POSS/08DTDMA), respectively, via ion-exchange
reaction. The interlayer space, interlamellar structure, thermal and
surface properties of these organo-montmorillonites were investigated by
X-ray diffraction, thermogravimetric analysis, and contact angle
measurement. The interlayer space of POSS modified clay was strongly
dependent on the arrangement of POSS surfactants, but less on the POSS
concentration. The POSS modified montmorillonites have partially exchanged
silicate surfaces and good thermal stabilities due to steric hindering and
thermal stability of the POSS molecules. Dual-surfactant modified
montmorillonites showed higher exchange ratio and possessed better
compatibility with PA12 due to the lower interfacial free energy. Polyamide
12-montmorillonite nanocomposites were prepared by conventional melt
compounding with the four POSS based organo-montmorillonites. The best
dispersion of modified montmorillonite was observed for 3mass%
04AP-POSS/08DTDMA/MMT filled PA12 nanocomposites, which resulted in the
best mechanical performance with an increase of 60% in tensile modulus and
10% in yield strength, respectively, compared to that of pure PA12.
Compatibility between montmorillonites and polymer was not the only key
factor affecting dispersion, thermal stability and interlayer space were
also crucial for good dispersion of montmorillonites in polymer matrix.
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