Ramie, also called China grass (Boehmeria nivea
(L.) Gaud.), is a hardy perennial herbaceous plant
of the Urticaceae family, which can be harvested
up to six times a year. It is mainly planted in
China and other Asian countries including Philippines,
India, South Korea, and Thailand (Liu
et al. 2001). Ramie fiber, stripped from stem bast
of the plant, has excellent properties such as high
tensile strength, excellent thermal conductivity,
coolness, ventilation function, moisture absorption,
antibacterial function and so on when it is
used as a textile material (Goda et al. 2006).However, there exist some disadvantages in the
processing of ramie fiber, such as the poor
capability of dyeing and the easy corrugation,
which hinder its wide applications.
It is commonly recognized that, native cellulose
like ramie fiber consists of linear macromolecules,
which is formed by b-d-anhydroglucose units and
linked together by 1,4-glucosidic bonds (Fig. 1,
Liu et al. 2006). Cellulose chains in solid state are
able to form intra- and inter-molecular hydrogenbonds,
leading to organized chain structure (Brant
and Goebel 1972). Thus ramie fiber can be
regarded as a highly crystalline fiber, in which
amorphous regions are formed by the most
extended stiff chains. The reactant molecules
cannot penetrate the highly ordered crystalline
regions of native cellulose and the reaction can
only take place in the amorphous regions and/or
the surface of the crystalline region. In order to
improve the reactivity of ramie fiber, structural
modification is required.
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