27
on the results due to its influence on the solubility of monomers and counterions,
and the propensity of charge transfer from the propagation end which leads to a
termination of polymerization. Some selected examples of this method are
listed below.
Hui et al. (2018) grafted nylon 6 from carbon fibers in order to improve interfacial compatibility in the composites. For this, the fibers were first treated with nitric
acid followed by thionyl chloride (SOCl 2 ) to produce acyl groups on the surface,
and then the fibers were immersed in a molten solution of caprolactam to initiate
anionic polymerization catalyzed by the addition of NaOH. A similar approach was
used by Gao et al. (2017) to treat carbon fibers containing acyl groups with ethylene
glycol to produce hydroxyl groups, and then treated with glycidol to graft polyglycerol from fibers with anionic ring opening polymerization. With the same objective
in mind, Raghavendran and Drzal (2002) first metallized the carbon fibers with
butyl lithium in N,N,N′,N′-tetramethylethylenediamine, and then without removing
the excess reagent, they were further treated with saturated cyclic oligocarbonate or
methyl methacrylate solutions to graft bisphenol A polycarbonates and polymethyl
methacrylate onto the fibers by anionic polymerization. Tsubokawa et al. (1989)
suggested that carbon fibers containing carboxyl groups, when treated with potassium hydroxide to produce potassium carboxylate groups can initiate grafting by
anionic polymerization with epoxides and cyclic acid anhydrides. Kim et al. (1997)
also observed that a premetalization of Kevlar fibers, with sodium hydride, allows
the anionic polymerization of ε-carolactam from the fibers. Yoshikawa et al. (1998)
introduced amino groups onto carbon fibers by nitration followed by reduction with
sodium thiosulfate, and then initiated the cationic polymerization with isobutyl
vinyl ether under catalytic conditions using a mixture of trifluoroacetic acid and
zinc chloride. Carbon fibers have also been grafted with polyacetal groups by acylation followed by a treatment with silver perchlorate to produce acyl perchlorate
groups which initiated polymerizations with 1,3,5-trioxane and 1,3-dioxolane to
produce grafted polyacetals (Tsubokawa and Yoshihara 1994). A similar procedure
was used by Tsubokawa and Yoshihara (1993) for grafting styrene and N-vinyl-2pyrrolidone onto vinyl polymers.
3.2.3.2 Ring Opening Polymerization (ROP)
This method is used with cyclic monomers such as ε-caprolactones and lactides
with Lewis acids (e.g. Sn(II) 2-ethylhexanoate) or metal alkoxides (e.g. from aluminum) that act as catalysts or initiators (Schwach et al. 1997; Mecerreyes et al. 1999;
Jérôme and Lecomte 2008; Carlmark et al. 2012). Two mechanisms have been proposed for this type of polymerization: one involves the complexation of the metal
with the monomer carbonyl group, which allows the initiation of polymerization by
the addition of nucleophilic agents such as alcohols or water, while the other mechanism involves a ‘coordination-insertion’ mechanism, where the metal is coordinated
to the ring oxygen of the monomer, thus promoting polymerization by inserting
3 Reactive Modification of Fiber Polymer Materials for Textile Applications
on the results due to its influence on the solubility of monomers and counterions,
and the propensity of charge transfer from the propagation end which leads to a
termination of polymerization. Some selected examples of this method are
listed below.
Hui et al. (2018) grafted nylon 6 from carbon fibers in order to improve interfacial compatibility in the composites. For this, the fibers were first treated with nitric
acid followed by thionyl chloride (SOCl 2 ) to produce acyl groups on the surface,
and then the fibers were immersed in a molten solution of caprolactam to initiate
anionic polymerization catalyzed by the addition of NaOH. A similar approach was
used by Gao et al. (2017) to treat carbon fibers containing acyl groups with ethylene
glycol to produce hydroxyl groups, and then treated with glycidol to graft polyglycerol from fibers with anionic ring opening polymerization. With the same objective
in mind, Raghavendran and Drzal (2002) first metallized the carbon fibers with
butyl lithium in N,N,N′,N′-tetramethylethylenediamine, and then without removing
the excess reagent, they were further treated with saturated cyclic oligocarbonate or
methyl methacrylate solutions to graft bisphenol A polycarbonates and polymethyl
methacrylate onto the fibers by anionic polymerization. Tsubokawa et al. (1989)
suggested that carbon fibers containing carboxyl groups, when treated with potassium hydroxide to produce potassium carboxylate groups can initiate grafting by
anionic polymerization with epoxides and cyclic acid anhydrides. Kim et al. (1997)
also observed that a premetalization of Kevlar fibers, with sodium hydride, allows
the anionic polymerization of ε-carolactam from the fibers. Yoshikawa et al. (1998)
introduced amino groups onto carbon fibers by nitration followed by reduction with
sodium thiosulfate, and then initiated the cationic polymerization with isobutyl
vinyl ether under catalytic conditions using a mixture of trifluoroacetic acid and
zinc chloride. Carbon fibers have also been grafted with polyacetal groups by acylation followed by a treatment with silver perchlorate to produce acyl perchlorate
groups which initiated polymerizations with 1,3,5-trioxane and 1,3-dioxolane to
produce grafted polyacetals (Tsubokawa and Yoshihara 1994). A similar procedure
was used by Tsubokawa and Yoshihara (1993) for grafting styrene and N-vinyl-2pyrrolidone onto vinyl polymers.
3.2.3.2 Ring Opening Polymerization (ROP)
This method is used with cyclic monomers such as ε-caprolactones and lactides
with Lewis acids (e.g. Sn(II) 2-ethylhexanoate) or metal alkoxides (e.g. from aluminum) that act as catalysts or initiators (Schwach et al. 1997; Mecerreyes et al. 1999;
Jérôme and Lecomte 2008; Carlmark et al. 2012). Two mechanisms have been proposed for this type of polymerization: one involves the complexation of the metal
with the monomer carbonyl group, which allows the initiation of polymerization by
the addition of nucleophilic agents such as alcohols or water, while the other mechanism involves a ‘coordination-insertion’ mechanism, where the metal is coordinated
to the ring oxygen of the monomer, thus promoting polymerization by inserting
3 Reactive Modification of Fiber Polymer Materials for Textile Applications