a novel oligomeric charring agent (PTCA) from nitrogen-based compounds, such as
cyanuric trichloride, diphenyl amine, and ethylene diamine, via nucleophilic reaction. Using a combination of PTCA with APP, they prepared FR polypropylene
(PP) composites and studied their thermal and FR activities. They observed that
20 wt% PP composites exhibited a high LOI value with significantly low PHRR,
THR, and TSR and also passed UL-94 with V-0 rating due to the synergetic effect
between PTCA and APP. The high thermal stability of these composites was
attributed to the formation of a stable highly graphitized aromatic char structure,
which was confirmed by FTIR analysis. Similarly, Xu et al. [5] synthesized highly
efficient FR PTPA and used it as a IFR in combination with APP for PPs.
They achieved excellent FR activity with a high LOI value and V-0 rating in UL-94
testing owing to the synergetic effect between PTPA and APP. Lv et al. [6] synthesized oligomeric FR and smoke suppression agents consisting of poly(melamineethoxyphosphinyl-diisocyanate) (PMPC) and used it a stand-alone FR for epoxy
resins; epoxy/PMPC composites with 20 wt% FR loading showed the highest LOI
value and achieved a V-0 rating. Most studies suggest that for acceptable FR activity,
more than 25 wt% IFR is required. However, such high loadings are detrimental to
the mechanical and physical properties of the polymer and increase the cost of
production. Combinations of N- and P-containing FRs, exhibit efficient FR activity
even at low loadings owing to a synergetic reaction between nitrogen and phosphorus. Wang et al. [7] used several nitrogen-based compounds, such as adenine,
cytosine, uracil, and guanine, obtained from bio-based gas sources along with an IFR
to improve the fire-retardancy of PP. They observed that PP containing 17 wt% of
IFR and 1 wt% of cytosine or uracil showed self-extinguishing ability with high LOI
values and passed the UL-94 test; on the other hand, PP containing same percentages
of adenine or guanine did not pass the UL-94 test. This indicates that cytosine and
uracil compounds are efficient in improving the FR activity of polymers due to the
formation of a stable cellular structure, which acts as a barrier to prevent the
exchange of gas and heat between the resin and outside environment. Hu et al. [8, 9]
synthesized a novel FR containing triazine (CA) and used it in combination with
APP in low-density polyethylene (LDPE); they observed that a 11% APP and 4%
CA-containing system showed high FR activity and thermal stability due to the
synergetic effect between APP and CA. Similarly, Li et al. [10] synthesized a
char-forming agent (CFA) from cyanuric chloride, ethylene diamine, and ethanolamine according to the reaction shown in Scheme 4.1. The char forming agent
(CFA) is a type of triazine-containing polymer, which can be used as a FR in
combination of APP for PP. The authors observed that 64% APP, 32% CFA, and 4%
zeolite containing system exhibited efficient IFR activity with high LOI value 30.2%
and passed UL-94 test. However, they assumed IFR activity without given proper
mechanism of FR activity.
Wang et al. [11] synthesized an IFR agent, PEPAPC, from the nitrogen-based
compounds, cyanuric chloride, PEPA (2,6,7-trioxa-1-phosphabicyclo[2.2.2] octane4-methanol), and piperazine, by nucleophilic substitution, as shown in Scheme 4.2.
They used PEPAPC with APP to prepare FR polypropylenes at different ratios;
at 20% FR loading (APP:PEPAPC = 3:1), the highest LOI value was obtained
16
4 Types of Flame Retardants Used for the Synthesis of …
cyanuric trichloride, diphenyl amine, and ethylene diamine, via nucleophilic reaction. Using a combination of PTCA with APP, they prepared FR polypropylene
(PP) composites and studied their thermal and FR activities. They observed that
20 wt% PP composites exhibited a high LOI value with significantly low PHRR,
THR, and TSR and also passed UL-94 with V-0 rating due to the synergetic effect
between PTCA and APP. The high thermal stability of these composites was
attributed to the formation of a stable highly graphitized aromatic char structure,
which was confirmed by FTIR analysis. Similarly, Xu et al. [5] synthesized highly
efficient FR PTPA and used it as a IFR in combination with APP for PPs.
They achieved excellent FR activity with a high LOI value and V-0 rating in UL-94
testing owing to the synergetic effect between PTPA and APP. Lv et al. [6] synthesized oligomeric FR and smoke suppression agents consisting of poly(melamineethoxyphosphinyl-diisocyanate) (PMPC) and used it a stand-alone FR for epoxy
resins; epoxy/PMPC composites with 20 wt% FR loading showed the highest LOI
value and achieved a V-0 rating. Most studies suggest that for acceptable FR activity,
more than 25 wt% IFR is required. However, such high loadings are detrimental to
the mechanical and physical properties of the polymer and increase the cost of
production. Combinations of N- and P-containing FRs, exhibit efficient FR activity
even at low loadings owing to a synergetic reaction between nitrogen and phosphorus. Wang et al. [7] used several nitrogen-based compounds, such as adenine,
cytosine, uracil, and guanine, obtained from bio-based gas sources along with an IFR
to improve the fire-retardancy of PP. They observed that PP containing 17 wt% of
IFR and 1 wt% of cytosine or uracil showed self-extinguishing ability with high LOI
values and passed the UL-94 test; on the other hand, PP containing same percentages
of adenine or guanine did not pass the UL-94 test. This indicates that cytosine and
uracil compounds are efficient in improving the FR activity of polymers due to the
formation of a stable cellular structure, which acts as a barrier to prevent the
exchange of gas and heat between the resin and outside environment. Hu et al. [8, 9]
synthesized a novel FR containing triazine (CA) and used it in combination with
APP in low-density polyethylene (LDPE); they observed that a 11% APP and 4%
CA-containing system showed high FR activity and thermal stability due to the
synergetic effect between APP and CA. Similarly, Li et al. [10] synthesized a
char-forming agent (CFA) from cyanuric chloride, ethylene diamine, and ethanolamine according to the reaction shown in Scheme 4.1. The char forming agent
(CFA) is a type of triazine-containing polymer, which can be used as a FR in
combination of APP for PP. The authors observed that 64% APP, 32% CFA, and 4%
zeolite containing system exhibited efficient IFR activity with high LOI value 30.2%
and passed UL-94 test. However, they assumed IFR activity without given proper
mechanism of FR activity.
Wang et al. [11] synthesized an IFR agent, PEPAPC, from the nitrogen-based
compounds, cyanuric chloride, PEPA (2,6,7-trioxa-1-phosphabicyclo[2.2.2] octane4-methanol), and piperazine, by nucleophilic substitution, as shown in Scheme 4.2.
They used PEPAPC with APP to prepare FR polypropylenes at different ratios;
at 20% FR loading (APP:PEPAPC = 3:1), the highest LOI value was obtained
16
4 Types of Flame Retardants Used for the Synthesis of …