Polyethylene‐encapsulated cellulose

Abstract

An encapsulation process is described in which cellulose fibers were enveloped with sheaths of polyethylene by the use of transition‐metal catalysts. Cellulose‐catalyst interactions resulted in a fiber surface completely covered with initiating sites, and growth of polymer occurred from the fiber surface outward to form a shell around each individual fiber. Removal of moisture and in situ catalyst formation were found to be essential for successful encapsulation. Catalyst interactions during different stages of formation were studied by following the absorption of the various catalyst components on cellulose. Active sites on fiber surfaces were postulated to have been formed by interaction with TiCl₄ and by reaction of reduced transition metal compounds with electron donor groups in the cellulose. Polymer growth was followed in a series of electron microphotographs and polyp‐like spherical polyethylene particles were observed at an early stage in the polymerization. It was concluded that encapsulation was a chemical means of placing polymer around a fiber core and not a grafting reaction. Fiber properties, uses of encapsulated cellulose, and conversion into web structures by use of paper making techniques were also discussed.