We present a novel approach to improving organoclay exfoliation in a nonpolar matrix, polyethylene. High-density polyethylene (HDPE) particles were modified by exposure to a reactive gas atmosphere containing F 2 and O 2 . This treatment was aimed at increasing the polarity of the polymer with the formation of carboxyl, hydroxy, and ketone functionalities on the particle surface. The surface-treated high-density polyethylene (ST-HDPE) particles were then melt-mixed with an appropriate organoclay to form nanocomposites. Transmission electron microscopy (TEM), wide-angle X-ray scattering, stress-strain analysis, and Izod impact measurements were used to evaluate the nanocomposite morphology and physical properties. These data were compared to those of equivalent nanocomposites prepared from unmodified HDPE and high-density polyethylene grafted with maleic anhydride (HDPE-g-MA). The nanocomposites prepared from the ST-HDPE particles exhibited much better properties and organoclay dispersion than those prepared from unmodified HDPE. The level of reinforcement observed in ST-HDPE-based nanocomposites was comparable to, if not better than, that seen in HDPE-g-MA-based nanocomposites. However, a comparison of the TEM micrographs suggested better organoclay exfoliation in HDPE-g-MA than the current version of ST-HDPE.

Ultrahigh molecular weight polyethylene (UHMWPE) powder (60 micron diameter) and chopped fiber (6.5 mm length) were surface treated with a blend of reactive gases (fluorine and oxygen.) These powders and fibers were then compounded into a thermoset polyurethane matrix. Surface‐treated and control reinforcements are compared at a 10 vol.% loading level. Tensile testing indicates improved stress transfer with surface treatment. Stress transfer is also improved with fibers versus powders. Fracture toughness is characterized by measuring the essential work of fracture, we. Surface‐treated fiber composites exhibit work of fracture values almost three times the unfilled polyurethane values. Abrasion resistance was also measured. Surface treatment was found to significantly lower wear rates of powder composites. Fiber composites had lower wear rates than powder composites, although surface treatment had little effect. An approximate inverse relationship was found between wear rate and essential work of fracture.

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Snrn maryUpon sterilization, freeze-dried kefir grains are to be supplemented with yeast preparation, yeast showing the lowest survival in the coiirse of freeze drying.-1 mixture of 20% sucrose solution and starch appeared to be the most efficient dispersing agent to protect yeast in the freeze-drying process. A st,nrter which is produced with the kefir starter culture, does not differ in its microbiological, biochemical and organoleptic properties from i starter as obtained with kefir groins in the same time, such starter shows a better consistency. The preparation of such starters is less laborious and less complicated than the preparation of starters using kefir grains.

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