Polyolefin-clay

It is generally accepted that thermal stability of polymer nanocomposites is higher than that of pristine polymers, and that this gain is explained by the presence of anisotropic clay layers hindering diffusion of volatile products through the nanocomposite material. It is important to note that the exfoliated nanocomposites, prepared and investigated in this work, had much lower gas permeability in comparison with that of pristine unfilled PE [12], Thus, the study of purely thermal degradation process of PE nanocomposite seemed to be of interest in terms of estimation of the nanoclay barrier effects on thermal stability of polyolefin/clay nanocomposites. 

Synthesizing a Polyolefin-Clay Nanocomposite Using the Polymerization Method... 

Hasegawa, N., Okamoto, H., Kawasumi, M., Kato, M., Tsukigase, A., and Usuki, A. 2000. Polyolefin-clay hybrids based on modified polyolefins and organophilic clay. Macromolecular Materials and Engineering 280-281 76-79. 

Tjong, S. C. and Ruan, Y. H. 2008. Fracture behavior of thermoplastic polyolefin/clay nanocomposites. Journal of Applied Polymer Science 110 864-871. 

Homogeneous" Polyolefin-Clay Composites by Polymerization Filling.131... 

Toward Polyolefin-Clay Nanocomposites by In Situ Polymerization.134... 

A viable process for manufacturing polyolefin-clay nanocomposifes by in situ polymerization requires adequate catalytic activity, desirable polymer microstructure, and physical properties including processibility, a high level of clay exfoliation fhaf remains stable under processing conditions and, preferably, inexpensive catalysf components. The work described in the previous two sections focused on achieving in situ polymerization with clay-supported transition metal complexes, and there was less emphasis on optimization of polymer properties and/or clay dispersion. Since 2000, many more comprehensive studies have been undertaken that attempt to characterize and optimize the entire system, from the supported catalyst to the nanocomposite material. The remainder of this chapter covers work published in the past decade on clay-polyolefin nanocomposites of ethylene and propylene homopolymers, as well as their copolymers, made by in situ polymerization. The emphasis is on the catalyst compositions and catalyst-clay interactions that determine the success of one-step methods to synthesize polyolefins with enhanced physical properties. 

The preparation of polyolefin-clay nanocomposites with nanodispersions that remain stable during processing, even at elevated temperatures, remains an important goal. For many potential applications, commercial success will preclude the use of large amounts of expensive compatibilizing agents. A promising approach is the in situ polymerization of... 

Peoples, B. C. 2008. In situ production of polyolefin-clay nanocomposites. PhD thesis. University of California, Santa Barbara. 

Evidences of Polymer/Clay Interaction and Confinement in Polyolefin/Clay... 

Passaglia, E., Bertoldo, M., Goiai, S., Augier, S., Savi, S., and Giardelli, E. 2008c. Nanostructured polyolefins/clay composites Role of the molecular interaction at the interface. Polymers for Advanced Technologies 19 560-568. 

Polyolefins are a major class of commodity synthetic polymers. The technology for the production of these important polymers is well estabUshed, from catalyst synthesis to polymerization reactor technology. Despite constant advancements in polyolefin production technology, applications of polyolefins are stiU mainly limited to commodity products. The recent interest in the production of polyolefin-clay nanocomposites extends the use of polyolefins to specialty and engineering plastic appHcations. Polyolefin-clay nanocomposites are lighter than conventional composites, but have thermal stability, barrier, and mechanical properties that are comparable to those of engineering plastics. 

As an alternative to melt mixing, in-situ polymerization is an attractive technique for the preparation of polyolefin-clay nanocomposites because it can promote better clay exfoliation and dispersion in the polymer matrix [1]. During in-situ polymerization, a coordination catalyst (such as Ziegler-Natta, metallocene, or late transition metal complex) is supported onto the clay interlayer surface to make polyolefin chains directly between the clay layers, leading to their exfoliation and dispersion into the polymer phase. 

Olefin in-situ polymerization methods for the production of polyolefin-clay nanocomposites still face many challenges before becoming industrially relevant. 

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