ABSTRACT
Submicrometer size particles of ultrahigh molecular weight polyethylene (UHMWPE) were produced by crystallization from dilute (0.1-1.0 wt % of UHMWPE) solvent/nonsolvent emulsions. The procedure consisted of mixing a hot solution of UHMWPE in decalin or decane with a nonsolvent (tetraglyme) at approximately 160 degrees C, followed by rapid cooling of the mixture to zero or subzero temperatures. The rapid cooling causes microphase separation between the two liquids, resulting in the formation of an emulsion, which consists of microdroplets of the supercooled UHMWPE solution dispersed in tetraglyme. The consequent crystallization of the polymer in the microdroplets produces a suspension of fine crystals of UHMWPE, which can easily be isolated. The particles were characterized using scanning electron microscopy, differential scanning calorimetry, and Raman spectroscopy. Their degree of crystallinity is between that of GUR 1050 original (powder) and processed (molded) polymer. By changing the polymer concentration, solvent to nonsolvent ratio, and temperature, the size (from 0.1-1.0 microm) and shape (spheroids or rods) of the particles can be controlled. These particles may be used for immunochemical investigations and the study of the influence of UHMWPE wear debris on cell response.