The purpose of this work is 2-fold: to describe a simple
and fast esterification pathway for lignin modification and
to obtain an esterified kraft lignin soluble in styrene. Since
styrene is the most commonly used reactive diluent in
unsaturated thermosetting polymers, in which it is the most
nonpolar component, styrene solubility will allow these
lignins to be used as additive to this polymer class. Lignin
is expected to improve the properties of bio- and petroleumbased
composites by (a) acting as a toughening agent, (b)
improving the connectivity in the network, (c) adding
additional stiffening groups to the matrix, (d) acting as a
sizing agent between natural fibers and the resin matrix, (e)
behaving as a comonomer for the resin, (f) inducing plasticity
in the deformation zone at crack tips to improve toughness,
(g) acting as a free radical trap to reduce radical scission
effects during fracture in highly cross linked polymers, (h)
improving flame resistance, (i) modifying biodegradability,
(j) providing enhanced photoresistance and thermal stability,
(k) expanding fatigue lifetime, and (l) contributing to the
green engineering of materials.41-43 A following publication
will describe the effect of the modified lignin on the
polymerized unsaturated thermosetting resins