(where ABS could simply be considered as an inert component), and the intramolecular reaction could be affected by the processing conditions, such as blending
temperature and duration. However, tensile properties of the in situ composites are
not linearly dependent on the degree of transesterification. The improved compatibility was not always favorable for the microfibrillation of PHBDET in PC-ABS
(Chen et al. 2009b). Additionally, the authors proved that a certain extent of
transesterification showed a positive influence on the tensile properties of the
composites by enhancing the interfacial adhesion between PC and PHDDT phases.
By applying a proper processing condition, the composites with expected in situ
reinforcement could be achieved.
Thermotropic Liquid Crystalline Polymers with High Flame
Retardance
Although the majority of the commercial TLCPs are highly resistant to fire due to
their high aromatic constitution and charring tendency thereof, which allows them as
the inherent flame-retardant engineering materials in many fields, as flame retardants, these TLCPs should be further modified. Introducing the flame-retardant
elements (phosphorus for instance) into the molecules of TLCP before blending
the TLCP into the required polymer matrix to make up the in situ composites is
supposed to be a good way to resolve the contradiction between flame retardance and
mechanical properties of traditional flame-retardant materials. Also, these TLCPs
with flame-retardant elements considered as polymeric flame retardants exhibit
much lower PBT profile when compared to small molecules. The key factor to
approaching an expected in situ composite with both flame retardance and reinforcement is to design a TLCP with suitable transition temperature (to meet the processing
temperature of the matrices), appropriate compatibility (between TLCP and matrix),
and adequate flame-retardant monomer content (to achieve a desirable flame
retardance). For TLCP with high flame retardance, phosphorus-containing compounds containing reactive functional groups that can be copolymerized either in
the side group or in the main chain are widely used to enhance the flame retardance
of TLCPs (Chen et al. 2014).
Side-Group Phosphorus-Containing TLCP
Among the phosphorus-containing moieties, DOPO (9,10-dihydro-9-oxa-10phosphaphenanthrene 10-oxide, Scheme 1) is the most commonly used one both as
precursor for a flame-retardant additive and as an integrative flame-retardant monomer.
DOPO is a phosphaphenanthrene homologue, derived from o-phenylphenol and phosphorus trichloride. The first synthesis of DOPO was reported by Sanko Chemical
(Japan) in 1972 (Saito 1972) and originally this compound was designed and utilized
for Toyobo’s flame-retardant polyester fibers and textiles. The reactive P–H bond of
DOPO can easily react with activated unsaturated bonds, such as acrylates (C=C),
20 Highly Flame-Retardant Liquid Crystalline Polymers
555
temperature and duration. However, tensile properties of the in situ composites are
not linearly dependent on the degree of transesterification. The improved compatibility was not always favorable for the microfibrillation of PHBDET in PC-ABS
(Chen et al. 2009b). Additionally, the authors proved that a certain extent of
transesterification showed a positive influence on the tensile properties of the
composites by enhancing the interfacial adhesion between PC and PHDDT phases.
By applying a proper processing condition, the composites with expected in situ
reinforcement could be achieved.
Thermotropic Liquid Crystalline Polymers with High Flame
Retardance
Although the majority of the commercial TLCPs are highly resistant to fire due to
their high aromatic constitution and charring tendency thereof, which allows them as
the inherent flame-retardant engineering materials in many fields, as flame retardants, these TLCPs should be further modified. Introducing the flame-retardant
elements (phosphorus for instance) into the molecules of TLCP before blending
the TLCP into the required polymer matrix to make up the in situ composites is
supposed to be a good way to resolve the contradiction between flame retardance and
mechanical properties of traditional flame-retardant materials. Also, these TLCPs
with flame-retardant elements considered as polymeric flame retardants exhibit
much lower PBT profile when compared to small molecules. The key factor to
approaching an expected in situ composite with both flame retardance and reinforcement is to design a TLCP with suitable transition temperature (to meet the processing
temperature of the matrices), appropriate compatibility (between TLCP and matrix),
and adequate flame-retardant monomer content (to achieve a desirable flame
retardance). For TLCP with high flame retardance, phosphorus-containing compounds containing reactive functional groups that can be copolymerized either in
the side group or in the main chain are widely used to enhance the flame retardance
of TLCPs (Chen et al. 2014).
Side-Group Phosphorus-Containing TLCP
Among the phosphorus-containing moieties, DOPO (9,10-dihydro-9-oxa-10phosphaphenanthrene 10-oxide, Scheme 1) is the most commonly used one both as
precursor for a flame-retardant additive and as an integrative flame-retardant monomer.
DOPO is a phosphaphenanthrene homologue, derived from o-phenylphenol and phosphorus trichloride. The first synthesis of DOPO was reported by Sanko Chemical
(Japan) in 1972 (Saito 1972) and originally this compound was designed and utilized
for Toyobo’s flame-retardant polyester fibers and textiles. The reactive P–H bond of
DOPO can easily react with activated unsaturated bonds, such as acrylates (C=C),
20 Highly Flame-Retardant Liquid Crystalline Polymers
555