Encapsulation of Pulp Fibers by Vanadium Trichloride-Catalyzed Polymerization of Ethylene

Abstract

A rapid process of encapsulating wood pulp is described. It involves first a reflux ing of cellulose with a solution of VCl₄ in heptane to thermally generate VCl₃ which forms crystals on the surface of cellulose fibers. These vanadium-covered fibers are suspended in a dilute triethylaluminum solution in heptane. Subsequent ethylene bubbling results in rapid encapsulation of individual fibers with high molecular-weight polyethylene. The process is rapid (100% weight increase in 5 min) and polyethylene is found only at fiber surfaces. Fiber cementation does occur, and it is relatively simple to control the thickness of the polymer sheath. Because of the relative uniformity of the polymer layer, significant surface property changes for the pulp fibers may be expected at relatively low add-ons. Polarized-light microscopy has shown that the added polymer layer around the fibers is birefringent due to a preferred tangential orientation of the growing chains.

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