Polymer/layered silicate nanocomposites by combined intercalative polymerization and melt intercalation: a masterbatch process

Abstract

Poly(ε-caprolactone) (PCL) and poly(vinyl chloride) (PVC) layered silicate nanocomposites were prepared by combination of intercalative polymerization and melt intercalation. In a first step, high clay content PCL nanocomposites were prepared by in situ polymerization of -caprolactone intercalated between selected organo-modified silicate layers. The polymerization was catalyzed with dibutyltin dimethoxide in the presence of montmorillonites, the surface of which were previously exchanged with (functionalized) long alkyl chains ammonium cations. Then, these highly filled PCL nanocomposites were added as masterbatches in commercial PCL and PVC by melt blending. The intercalation of PCL chains within the silicate layers by in situ polymerization proved to be very efficient, leading to the formation of intercalated and/or exfoliated structures depending on the organo-clay. These masterbatches were readily dispersed into the molten PCL and PVC matrices yielding intercalated/exfoliated layered silicate nanocomposites which could not be obtained by melt blending the matrix directly with the same organo-modified clays. The formation of nanocomposites was assessed both by X-ray diffraction and transmission electronic microscopy. Interestingly, this so-called 'masterbatch' two-step process allowed for preparing PCL nanocomposites even with non-modified natural clay, i.e. sodium montmorillonite, which showed a material stiffness much higher than the corresponding microcomposites recovered by direct melt intercalation. The thermal stability of PCL nanocomposites as a function of clay content was investigated by thermogravimetry (TGA).

Avaliação da morfologia e propriedades termo-mecânicas em nanocompósitos de PVC

“…Como pode ser visualizada, a dispersão da argila na matriz do PVC tende a formar alguns aglomerados com o aumento da concentração de 1% para 5%, por outro lado, parece apresentar um maior grau de intercalação e esfoliação tetraédricas externas é o óxido de silício, onde os átomos de silício estão ligados a quatro átomos de oxigênio [7][8][9][10] .…”

Advances in Polypropylene Based Materials

“…In this approach, PP-OH was intercalated between the layers of organo-modified montmorillonite, and then the product was melt mixed with PP to obtain the nanocomposite with intercalated structure. Many further investigations were reported on melt blending of PP, modified by maleic anhydride grafted polypropylene (mPP) used as a compatibilizer, with organo-clays [161][162][163][164][165][166][167]. A wide range of systems was investigated in order to promote polymer intercalation into the clay galleries, with variables being molecular weight of the PP, maleic anhydride content in the compatibilizer, clay modification and content, etc.…”

“…However, this could affect inversely the miscibility between the high-molecular weight matrix PP and the compatibilizer. Depending on a nanoscale dispersion of the layered silicate, the whole spectrum of structures, ranging from intercalated to exfoliated PP nanocomposites, have been observed by WAXD, SAX (see, for instance, Figure 4) and TEM [166,[169][170][171][172]. It is well known that functionalization with mPP could lead to chain scission of the PP, which, in turn, can drastically diminish the mechanical properties of final composite [172].…”

A Novel and Facile Nanoclay Aerogel Masterbatch toward Exfoliated Polymer-Clay Nanocomposites through a Melt-Mixing Process

“…e natural nanoclays are hydrophilic which is a problem for homogeneous dispersion in several polymers, so the nanoclays have to be developed to be an organoclay through the alkylammonium cation-exchange method [3,4].…”