Amine‐catalyzed polymer encapsulation of cotton fibers by vapor phase application of formaldehyde

A process for encapsulating cotton fibers in the form of woven clothes at ambient temperatures with polyoxymethylene is described. It involves pretreatment of the cotton with a carbon tetrachloride solution of tributylamine and diphenylamine to deposit the basic catalyst on the surface of the fibers. Subsequent exposure to dry, purified vapors of monomeric formaldehyde at 25°C results in the encapsulation of individual fibers with high molecular weight polyoxymethylene. The process is relatively fast (30% fiber weight gain in approx. 20 min) with the polymer located only at the fiber surfaces. Fiber cementation does not become pronounced for weight increases below approximately 60%–65% based upon the weight of the fibers. Thickness of the polymer sheath increases with the time of the polymerization reaction. Because of the uniformity of the polymer layer deposition, the encapsulated cotton cellulose fibers can be expected to exhibit substantially different physical and chemical surface properties even at low polymer add-on. The tensile and tear strengths of the polyoxymethylene-encapsulated cotton fibers are generally improved, with some gains in abrasion resistance also noted. Differential staining techniques and polarized light microscopy have shown the location and uniformity of the polymer sheaths.