Dynamic mechanical analysis, surface chemistry and morphology of alkali and enzymatic retted kenaf fibers

Bast fibers grow in the bark layer of many plants and have been used for textiles and cordage for over 6000 years. Bast fibers are expanding into new markets of non-woven fabrics and composite materials, and a comparative assessment of surface reactive groups and mechanical properties after different retting procedures is of value. Here, bast fiber of kenaf ( Hibiscus cannabinus L., Malvaceae) were prepared by (1) alkali retting with 2% NaOH and (2) enzymatic retting with pectinase, and compared with commercially-available fiber retted by the natural microbe population in ocean water. Fiber structure was analyzed by fluorescence and electron microscopy; fiber chemistry was assessed by Raman and X-ray photoelectron spectroscopy, and by carbohydrate analysis; and mechanical properties were determined by dynamic mechanical analysis. Collectively, these show that enzymatic and microbial retting preserve the natural fiber structure and result in superior mechanical properties compared with alkali retting, which disrupts structure and degrades quality. The impacts of the retting procedure on fiber chemistry, morphology and mechanical properties are discussed.