Extraordinary mechanical behavior of exfoliated montmorillonite/polymer nanocomposite films cast from soap-free emulsion polymerized latices
2010
Lin, Keng-Jen | Lee, Chia-Hsin | Lin, King-Fu
The exfoliated montmorillonite (MMT) nanoplatelets tended to re-stack with each other after casting the MMT/poly(methylacrylate-co-methylmethacrylate) P(MA-co-MMA) latex solutions fabricated by soap-free emulsion polymerization into films as revealed by X-ray diffraction and transmission electron microscopy. As the content of MMT was increased from 0 to 20 wt %, the Tg measured by differential scanning calorimetry was slightly decreased from 19.2 to 17.2 °C, whereas that measured by dynamic mechanical analysis was increased from 22 to 32 °C, indicating that the local motion of polymer segments has been retarded by MMT nanoplatelets. Besides, the elongated elliptical voids appeared during stretching of 1 wt % MMT/P(MA-co-MMA) film to cracking also illustrated the pinning effect provided by the exfoliated MMT. As the content of MMT was increased more than 10 wt %, the mechanical behavior of MMT/P(MA-co-MMA) nanocomposite films was changed from ductile to brittle nature with significant increase of Young's modulus and tensile strength owing to the restacking of exfoliated MMT nanoplatelets.
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