Clays composites

Micro-composites are formed when the polymer chain is unable to intercalate into the silicate layer and therefore phase separated polymer/clay composites are formed. Their properties remain the same as the conventional micro-composites as shown in Figure 2(a). Intercalated nano-composite is obtained when the polymer chain is inserted between clay layers such that the interlayer spacing is expanded, but the layers still bear a well-defined spatial relationship to each other as shown in Figure 2(b). Exfoliated nano-composites are formed when the layers of the day have been completely separated and the individual layers are distributed throughout the organic matrix as shown in Figure 2(c). 

FIG. 2 Schematic illustration of three types of polymer-clay composites. 

Heavy metals bound to bacteria-soil composites may not be as easily released to the environments as those sorbed by pure bacteria. Flemming et al. (1990) reported that the order of remobilization of heavy metals from bacteria-clay composites was Cr Ag < Cu. Chromium was veiy stable when sorbed by bacterial cell walls, clay, and bacterial wall-clay... 

Flemming CA, Ferris FG, Beveridge TJ, Bailey GW (1990) Remobilization of toxic heavy metals adsorbed to bacterial wall-clay composites. Appl Environ Microbiol 56 3191-3203... 

Polymer-Filler Composites thru In Situ Graft Copolymerization Polyethylene-Clay Composites... 

An evaluation of numerous clays, including kaolins and bentonites of comparable particle size and distribution, revealed a wide variation in the properties of LDEE-clay composites prepared under identical conditions with similar loadings. This may be attributed to the interference with the radical reactions involved in the coupling sequence. This is confirmed, in part, by the finding that the most effective clays were those which were reported to have been treated with sodium polyphosphate to improve their dispersibility in water during papermaking processes. Solomon reported (1) that treatment of the clays which inhibited radical reactions with sodium polyphosphate reduced the inhibition. 

These conditions are identical to those required for the homopolymerization of MAH, i.e. the catalyst has a half-life of up to about 30 min at the reaction temperature (6). Thus, t-butyl perbenzoate (tBPB) is effective in the preparation of LDEE-clay composites at 130 and 150 c and HDEE-clay composites at 150 C while dicumyl peroxide is less effective in LDFE-clay composites at 130 C than at 150 C. 

The effect of the components and conditions of preparation on the properties of a 70/30 LDPE/clay composite is shown in Table I. The 10/90 mixture of LDEE Bakelite Polyethylene Resin DYNH-1 (Union Carbide Corp.) and Hydrite 10 clay (Georgia Kaolin Co.) was compounded at 150 C in the Brabender Plasticorder in the presence of MAH and/or t-butyl perbenzoate (tBPB). The EE-coated clay was then mixed with additional DYNH-1 LDPE at 130°C to yield a 70/30 PE/clay composite. A 30 70 PE/clay concentrate was prepared in a similar manner at 150 C and converted to a 70/30 EE/ clay composite at 130 C. The 10/90 PE/clay concentrate is an easily handled, clay-like product while the 30/70 concentrate is... 

The influence of the various components of a HDPE/clay composite on the properties is shown in Table II. A 30/70 PE/clay concentrate was prepared from 15 parts HDPE Fortiflex A60-70R (Allied Chemical Corp.) and 35 parts of Hydrite 10 by mixing at 150 C in the presence of 3 parts of maleic acid (MA) and 0.75 parts of tBPB. The concentrate was then blended at 150 C with additional HDPE to yield a 50/50 HDPE/clay composite. 

The FE-MAH-clay composite prepared by the in situ polymerization of MAH in the presence of PE and clay actually contains three phases ... 

The level of clay loading dramatically influences the mechanical properties of HDPE Fortiflex A60-70R/Hydrite 10 clay composites prepared from MAH-tBPB coupled 30/70 PE/clay concentrates. The 30/70 HDPE/clay mixture was prepared either in the absence of MAH and tBPB or in the presence of 20% MAH and 5%tBPB, based on PE, at 150 C and then compounded with additional HDPE to yield the final PE/clay composites shown in Table III. 

The water vapor transmission of compatibilized PE/clay composites are lower than those of the unfilled PE and PE/clay mixtures and do not increase until the clay content is greater than 1+0%. The values are similar to those of crosslinked PE, in the absence of clay, and suggest that the clay acts as a crosslinking agent for the PE. 

The compatibilization of clay with LDPE and HDFE is accomplished by the in situ polymerization of MAH or its precursor maleic acid, in the presence of a radical catalyst. The latter must be capable of initiating the homopolymerization of MAH, i.e. it must be present in high concentration and/or have a half-life of less than 30 min at the reaction temperature, e.g. t-butyl per-benzoate (tBFB) at 150°C. In a one-step process, the clay and PE are mixed with MAH-tBPB in the desired PE/clay ratio. In the preferred two-step process, a 70/30-90/10 clay/PE concentrate is prepared initially in the presence of MAH-tBPB and then blended with additional PE to the desired clay loading. The compatibil-ized or coupled PE-MAH-clay composites have better physical properties, including higher impact strengths, than unfilled PE or PE-clay mixtures prepared in the absence of MAH-tBPB. 

The dye-clay composites were prepared by dispersing the clays in each solvent containing the dye at a quantity of 10-200% of the CEC. This experimental procedure led to almost complete intercalation at room temperature for 2-7 days. The composite was recovered by filtration and washing several times with each solvent for eliminating an excess of dye, and then dried in air. Assuming that the loss of dye adsorbed on the surface was fairly small upon washing, the net weight of dye intercalated was estimated from the residual dye concentration in a solvent measured by a colorimetric analysis. 

All experiments on the characterization of dye-clay composites were performed after drying overnight at 100°C in air, which should lead to the expulsion of... 

To return to our earlier point on the variation of clay compositions within the Valley of Mexico, Table VII shows the mean concentrations and standard deviation spreads of the Tlatilco, Teotihuacan, and Oaxacan matching groups. These data show that the Tlatilco and Teotihuacan... 

There have been a number of studies of polymers at surfaces, as illustrated in Figure 8, including some that have been tethered [10, 122-137]. Also in this category are the polymer-clay composites after the previously paired platelets have been sufficiently separated to be independent of one another. Such exfoliated arrangements are shown in Figure 9. 

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