condition, both flame retardance and mechanical properties, particularly tensile
properties, are enhanced considerably.
However, there are further challenges in the research of both highly flame-retardant
TLCP and the composites with both flame retardance and in situ reinforcement:
1. Developing more effective and economic flame-retardant monomer. Flame
retardance of the in situ composites comes from the copolymerizing monomer
with flame-retardant functional groups; therefore, the flame-retardant efficiency
and economic consideration become the first priority. Up to present, DOPOcontaining derivatives have been successfully commercialized; however, so far
the flame-retardant efficiency of DOPO-HQ demonstrated in the composites are
less than optimal. Also the contribution from the aromatic segments, particularly
the mesogenic units, shall not be ignored.
2. Synthesizing TLCP with lower liquid crystalline phase transition temperature and
wide temperature range of liquid crystalline phase. High orientation ability and
high shear thinning characteristics of TLCP are unique and beneficial during the
polymer processing; however, TLCPs are too viscous to flow at the temperature
below their T i , thus exhibiting poor melt processability. According to the aforementioned examples, the most commonly used strategy is to introduce multimethylene flexible spacers, but thermal stability, decomposition residue, and
potential flame retardance shall be sacrificed. Copolymerizing kinked units has
been established as the best alternative method, but the transition temperatures of
such TLCP are still high. Thus, further researches are extremely necessary.
3. Solving the factors influencing the fibrillation of TLCP in the matrix. Most TLCPs,
including phosphorus-containing TLCPs, are incompatible with thermoplastics,
leading to the properties of the TLCP/thermoplastic blends to fall short of expectations. Poor interfacial adhesion remains another major obstacle in achieving high
performance of the resulted in situ composites. And of course, the fibrillation,
morphology, and distribution of TLCP dispersed phase in the thermoplastic matrix
is greatly affected by the processing conditions. All the above-mentioned factors
suggested the procedures of microfibrillation and the corresponding in situ reinforcement are incredibly complicated. There are a lot of works to do.
Nevertheless, the exploration of the novel method for flame retardation of polymers with improved mechanical properties can be seen as a class of efficient flameretardant method, and hence provides a powerful basis for the construction of flameretardant technologies and potential industrial applications.
References
Bian XC, Chen L, Wang JS, Wang YZ (2010) A novel thermotropic liquid crystalline copolyester
containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature. J Polym Sci A Polym Chem 48:1182–1189
Bourbigot S, Duquesne S (2007) Fire retardant polymers: recent developments and opportunities.
J Mater Chem 17(22):2283–2300
20 Highly Flame-Retardant Liquid Crystalline Polymers
571
properties, are enhanced considerably.
However, there are further challenges in the research of both highly flame-retardant
TLCP and the composites with both flame retardance and in situ reinforcement:
1. Developing more effective and economic flame-retardant monomer. Flame
retardance of the in situ composites comes from the copolymerizing monomer
with flame-retardant functional groups; therefore, the flame-retardant efficiency
and economic consideration become the first priority. Up to present, DOPOcontaining derivatives have been successfully commercialized; however, so far
the flame-retardant efficiency of DOPO-HQ demonstrated in the composites are
less than optimal. Also the contribution from the aromatic segments, particularly
the mesogenic units, shall not be ignored.
2. Synthesizing TLCP with lower liquid crystalline phase transition temperature and
wide temperature range of liquid crystalline phase. High orientation ability and
high shear thinning characteristics of TLCP are unique and beneficial during the
polymer processing; however, TLCPs are too viscous to flow at the temperature
below their T i , thus exhibiting poor melt processability. According to the aforementioned examples, the most commonly used strategy is to introduce multimethylene flexible spacers, but thermal stability, decomposition residue, and
potential flame retardance shall be sacrificed. Copolymerizing kinked units has
been established as the best alternative method, but the transition temperatures of
such TLCP are still high. Thus, further researches are extremely necessary.
3. Solving the factors influencing the fibrillation of TLCP in the matrix. Most TLCPs,
including phosphorus-containing TLCPs, are incompatible with thermoplastics,
leading to the properties of the TLCP/thermoplastic blends to fall short of expectations. Poor interfacial adhesion remains another major obstacle in achieving high
performance of the resulted in situ composites. And of course, the fibrillation,
morphology, and distribution of TLCP dispersed phase in the thermoplastic matrix
is greatly affected by the processing conditions. All the above-mentioned factors
suggested the procedures of microfibrillation and the corresponding in situ reinforcement are incredibly complicated. There are a lot of works to do.
Nevertheless, the exploration of the novel method for flame retardation of polymers with improved mechanical properties can be seen as a class of efficient flameretardant method, and hence provides a powerful basis for the construction of flameretardant technologies and potential industrial applications.
References
Bian XC, Chen L, Wang JS, Wang YZ (2010) A novel thermotropic liquid crystalline copolyester
containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature. J Polym Sci A Polym Chem 48:1182–1189
Bourbigot S, Duquesne S (2007) Fire retardant polymers: recent developments and opportunities.
J Mater Chem 17(22):2283–2300
20 Highly Flame-Retardant Liquid Crystalline Polymers
571