Dynamics and Mechanism of Flame Retardants in Polymer Matrixes: Experiment and Simulation

Abstract

We investigate the dynamics and the mechanism of flame retardants in polycarbonate matrixes to explore for a way of designing efficient and environment-friendly flame retardants. The high phosphorus content of organic phosphates has been considered as a requirement for efficient flame retardants. We show, however, that one can enhance the efficiency of flame retardants even with a relatively low phosphorus content by tuning the dynamics and the intermolecular interactions of flame retardants. This would enable one to design bulkier flame retardants that should be less volatile and less harmful in indoor environments. UL94 flammability tests indicate that even though the phosphorus content of 2,4-di-tert-butylphenyl diphenyl phosphate (DDP) is much smaller with two bulky tertiary butyl groups than that of triphenyl phosphate (TPP), DDP should be as efficient of a flame retardant as TPP, which is a widely used flame retardant. On the other hand, the 2-tert-butylphenyl diphenyl phosphate (2-tBuDP), with a lower phosphorus content than TPP but with a greater phosphorus content than DDP, is less efficient as a flame retardant than both DDP and TPP. Dynamic secondary ion mass spectrometry and molecular dynamics simulations reveal that the diffusion of DDP is slower by an order of magnitude at low temperature than that of TPP but becomes comparable to that of TPP at the ignition temperature. This implies that DDP should be much less volatile than TPP at low temperature, which is confirmed by thermogravimetric analysis. We also find from Fourier transform infrared spectroscopy that Fries rearrangement and char formation are suppressed more by DDP than by TPP. The low volatility and the suppressed char formation of DDP suggest that the enhanced flame retardancy of DDP should be attributed to its slow diffusivity at room temperature and yet sufficiently high diffusivity at high temperature.

An Extremely Efficient Silylated Benzensulfonate Flame Retardant for Polycarbonate

“…Otherwise, the contents of both Si and S should decrease owing to the early degradation of KTSS. The migration of KTSS facilitated by the presence of the trimethylsilyl group is clearly consistent with a great diffusibility of the structurally similar bulky tert-butyl substituted phenyl phosphates [29]. Further, the migration of KTSS is strongly supported by a nearly constant ratio of K/S after 5 s, an expected result from the theoretical consideration.…”

“…1 H NMR (D2O): δ = 7.64, 7.68 (ABq, 3 JHH = 16 Hz, 4H, Ar-H), 0.17 (s, CH3-Si, 9H) ppm. 13 C NMR (D2O): δ = −2.34 (Si-CH3), 124.44 (C=C-SO3K), 133.95 (C=C-Si), 142.68 (C-SiMe3), 145.67 (C-SO3K) ppm; 29 Si NMR (D2O): δ = −3.52 ppm ( Figure S1).…”

“…1 H NMR spectrometry was performed on the Bruker 400 AVANCE spectrometer (Bruker Scientific, Billerica, MA, USA) at 400 MHz using D 2 O as solvent. 13 C NMR spectrum and 29 Si NMR spectrum of KTSS were obtained on the same instrument at 100 MHz and 79 MHz, respectively.…”

Antiflaming poly(L‐lactide) by synthesizing polyurethane with phosphorus and nitrogen

“…The polyphosphoric acid could help to form a continuous uneven char layer on the surface of PLLA composites, as exhibited in Figure 8(A), which prevent the transfer of combustible gas and heat; PO• and PO 2 • radicals could quench H• and HO• radicals to accelerate the formation of carbonaceous residue, and slow down combustion. 39 On the other hand, as shown in Figure 8(B), when the pressure of degradation gas under the char layer exceeded the pressure limit of the char layer on the polymer surface, the char layer would break and release nitrogen contained gas and free radicals. Where after, the release of nitrogen contained gases and phosphorus contained free radicals could retard combustion continuously.…”

In situ polymerization of flame retardant modification polyamide 6,6 with 2‐carboxy ethyl (phenyl) phosphinic acid

“…However, due to their corrosive and poisonous combustion products, they have been forbidden to use worldwide . The development of phosphorus, nitrogen, and silicon containing flame retardants has made flame retardant PA66 halogen‐free. So far, physical blending is the main technology applied in the flame retardance modification for PA66, that is, the flame retardants are mixed with PA66 and melt extruded to obtain flame retardance.…”