Toyota Research

Clays have long been used as fillers in polymer systems because of low cost and the improved mechanical properties of the resulting polymer composites. If all other parameters are equal, the efficiency of a filler to improve the physical and mechanical properties of a polymer system is sensitive to its degree of dispersion in the polymer matrix (Krishnamoorti et ah, 1996). In the early 1990s, Toyota researchers (Okada et ah, 1990) discovered that treatment of montmorillonite (MMT) with amino acids allowed dispersion of the individual 1 nm thick silicate layers of the clay scale in polyamide on a molecular. Their hybrid material showed major improvements in physical and mechanical properties even at very low clay content (1.6 vol %). Since then, many researchers have performed investigations in the new field of polymer nano-composites. This has lead to further developments in the range of materials and synthesizing methods available. 

However, the field of polymer day silicate has only started to speed up recently, mixing the appropriate modified layered silicate with synthetic layered silicates has long been known (Theng, 1979). The interest in these materials came from two important findings, first has been reported by Toyota research group of a Nylon-6 (N6)/Na-MMT nano-composites (Okada et ah, 1990) where very small amounts of layered silicate loadings resulted in the improvements of thermal and mechanical properties and second the findings of Vaia et ah (1993) about the... 

The data provided by Toyota Research Group of Japan on polyamide-MMT nanocomposites indicate tensile strength improvements of approximately 40%-50% at 23°C and modulus improvement of about 70% at the same temperature. Heat distortion temperature has been shown to increase from 65°C for the unmodified polyamide to 152°C for the nanoclay-modified material, all the above having been achieved with just a 5% loading of MMT clay. Similar mechanical property improvements were presented for polymethyl methacrylate-clay hybrids [27]. 

Rana Mohtadi, Toyota Research Institute of North America Ann Arbor, Ml, USA Kyoichi Tange, Tomoya Matsunaga Toyota Motor Corporation, Susono, Shizuoka, Japan George Wicks, Kit Heung, Ray Schumacher, Savannah River National Laboratory, Aiken, SC, US... 

Many researchers have shown that incorporation of nanoscale dimension particles (inorganic fillers, nanotubes, nanofibers etc) into a polymer matrix enhances the mechanical properties of the polymer without significantly raising its density or sacrificing its light transmission property. For instance, the Toyota research groups... 

The earliest study cited for the preparation of novolac-layered silicate nanocomposites was reported by scientists from the Toyota Research Center. Usuki et al. modified a sodium-type montmorillonite (MMT) clay with 4-aminophenol hydrochloride in water. The... 

Research Scientist, Lab M-3 Materials Research Department Toyota Research Institute of North America Toyota Motor Engineering ... 

A further group of nanocomposites are the well-known bentonites, revitalized at the end of the 1980s by Toyota Research. Bentonites are swellable, three-layer silicates consisting mainly of montmorillonite. The new organophilic bentonite Nanofil product family from Siid Chemie AG is based partly on the Bavarian calcium bentonites, which are activated by acid leaching [see Table 27 [77]], and do without cationic exchange. (Author s remark With a mean particle size of 4 pm, these are by no means nanoparticles ). 

Layered sdicate/polymer nanocomposites were first reported in 1950 as a patent literature (Carter et al.,1950). ITowever, it was not popular until Toyota researchers began a detailed... 

Takatori and his collaborators in Toyota Research Center were one of the first who developed and systematically studied the emulsion combustion method (ECM) [3]. This method is basically a combination of the microemulsion wet chemistry and the flame spray pyrolysis methods. In ECM, an aqueous solution of a metal salt is mixed with a fuel such as kerosene and a small amount of an emulsifier or surfactant to obtain a water-in-oil (W/O) type of emulsion. Using a spray nozzle, the solution is then atomized to produce a spray. The size of the mother emulsion droplets depends on the atomizer type and the atomization conditimis, and is on the order of 10 pm for air-assist nozzles. The size of the dispersed micro-solution droplets depends on the string process and surfactant, and is about 1 pm [3]. Figure 40.1 shows a schematic diagram of the ECM. 

Clay-polymer nanocomposites, a new class of hybrids, came into the purview of researchers after their invention by the Toyota research group [7,8]. They found dramatic improvement in tensile properties of polymers by adding clay in small weight fractions. In continuation of this, other researchers have used various techniques to develop polymer nanocomposites with clay as reinforcement after proper organic treatment. 

Depending on the distribution of micro/nanofiller in the polymer matrix, the composites may be classified as microcomposites or nanocomposites. These two types of composites differ significantly with respect to their properties. The nanocomposites show improved properties compared to pure polymer or that of microcomposites. It started only back in 1990, when Toyota research group showed that the use of montmorillonite can improve the mechanical, thermal, and flame retardant properties of polymeric materials without hampering the optical translucency behaviour of the matrix. Since then, the majority of research has been focused in improving the physicochemical properties, e.g. mechanical, thermal, electrical, barrier etc. properties of polymer nanocomposites using cost effective and environmental friendly nanofillers with the aim of extending the applications of these materials in automotive, aerospace, construction, electronic, etc. as well as their day to day life use. The improvements in the majority of their properties have invariably been attributed... 

NCH Nylon-Clay Hybrid polyamide-6 with montmorillonite particles 0.1-0.2 run diameter nanometer composite developed by Toyota Research Corp. Ube Industries, LuL... 

It was the pioneering work of Toyota researchers toward the development of polymeric nanocomposites in the early 90s [1, 2], in which electrostahcally held 1-nm-thick layers of the layered aluminosilicates were dispersed in the polyamide matrix on a nanometer level, which led to an exponenhal growth in the research in these layered silicate nanocomposites. These nanocomposites were based on the in-situ synthesis approach in which monomer or monomer solution was used to swell the filler interlayers followed by polymerizahon. Subsequently, GianneUs and CO workers [3, 4] also reported the route of melt intercalation for the synthesis of polymer nanocomposites. 

In-situ intercalation method was reported by Toyota researchers for the synthesis of polyamide nanocomposites that led to the exponential growth in the nanocomposites research. For generation of polymer nanocomposites by this method, the layered silicate mineral is swollen in monomer. After swelling, the polymerization of the monomer is initiated. As monomer is present in and out of the filler interlayers, therefore, the generated stmcture is exfoUated or significantly intercalated. As the rate or mechanism of polymerization in and out of the filler interlayers... 

PNGs modified with nanoclays show remarkable increases in thermomechanical properties. The clay-nylon PNC Toyota Research produced for under-the-hood applications in the Toyota Camry is a good example. By incorporating a small amount of MMT clay into a nylon matrix, the heat distortion temperature of the composite increased by 87 °C, allowing its use in under-the-hood automobile components [54]. 

TOYOTA RESEARCH INSTITUTE OF NORTH AMERICA, ANN ARBOR, Ml, USA, TOYOTA MOTOR EUROPE NV/SA, ZAVENTEM, BELGIUM, TOYOTA MOTOR CORPORATION, SUSONO, SHIZUOKA, JAPAN CORRESPONDING AUTHORS FUMINORI.MIZUNO TEMA.TOYOTA.COM, CHIHIRO.YADA TOYOTA-EUROPE.COM, IBA ATOM.TEC.TOYOTA.CO.JP... 

Toyota Research Institute of North America, Ann Arbor, Ml, USA Paul A. Nelson... 

Exfoliated clay nanocomposites formed between organocation exchanged montmorillonites and thermoplastic Nylon-6 have recently been described by Toyota researchers (9-11). Clay exfoliation in the Nylon-6 matrix gave rise to greatly improved mechanical, thermal and rheological properties, mal g possible new materials applications of this polymer. However, it is relatively difficult to achieve complete exfoliation of smectite clays into a continuous polymer matrix, because of the strong electrostatic attraction between the silicate layers and the intergallery cations. 

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