Polyethylene/clay crystallization

Solution blending Polar as well as nonpolar solvents can be used in this method. The polymer is solubilized in a proper solvent and then mixed with the filler dispersion. In solution, the chains are well separated and easily enter the galleries or the layers of the fillers. After the clay gets dispersed and exfoliated, the solvent is evaporated usually under vacuum. High-density polyethylene [24], polyimide (PI) [25], and nematic hquid crystal [26] polymers have been synthesized by this method. The schematic presentation is given in Scheme 2.2. 

C and increased both the modulus and crystallization rate three fold.234 (Slow crystallization of this polymer leads to uneconomically long cycle times in molding.) Similar techniques have used to add clays into polyethylene,235 polypropylene,236 and epoxy resins.237... 

Aluminum foil is added piece-by-piece to 15% HF solution contained in a platinum dish. The reaction temperature is maintained below 25°C by periodic dipping of the dish in an ice-water bath. After some time, the initial rather vigorous reaction virtually ceases even upon addition of further quantities of aluminum. The solution is filtered through a polyethylene filter into a polyethylene dish additional pieces of aluminum foil are added to the filtrate, and the latter is allowed to crystallize in a refrigerator for 24 hours. The crystals are washed with some water and dried at room temperature on a clay plate. 

More recently, the same research group also reported that in hydro-calcite nanoparticle modified PE fibers [21] the incorporation of clay improved the thermal stability and induced heterogeneous nucleation of polyethylene crystals. Hydrocalcite exhibited good dispersion into the polymer matrix, and hence positively affected the mechanical properties in terms of both stiffness and strength. The toughness of the nanocomposite as spun fibers was also increased up to 30% with respect to neat polymer. 

HDPE/bamboo composites with different nanoclay and maleated polyethylene (MAPE) contents were fabricated by melt compounding. The compounding characteristics, clay dispersion, HOPE crystallization, and mechanical properties of the composites were studied. The X-ray diffraction (XRD) data showed that the clay was exfoliated only when 1% clay was added to pure HOPE wifliout MAPE. For HDPE/bamboo systems, MAPE was necessary to achieve clay exfoUatiOTi. For the HDPE/bamboo fiber composites, tensile strength, bending modulus, and strength were improved with the use of MAPE however, the use of the clay in the system led to reduced mechanical properties [27]. 

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