Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon

Abstract

The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable.

Design and Application of Highly Efficient Flame Retardants for Polycarbonate Combining the Advantages of Cyclotriphosphazene and Silicone Oil

“…This may be because the HSPCTP additive decomposes and promotes the degradation and charring of the PC matrix earlier. Besides, silicon oxide derivatives and phosphoric acid derivatives are produced by decomposition of HSPCTP, which promotes decomposition of PC [5,20,30,31]. Figure 5b and Table 3 show that the THR curve of PC/HSPCTP3 composites is lower than that of pure PC, and the THR value decreased from 71.56 to 59.11 MJ/m 2 .…”

“…Another reason is that the silica derivatives react with the PC chain to produce a cross-linked structure, which also promotes the formation of a compact carbon layer. In addition, phosphorus, nitrogen and benzene ring structures can also promote the formation of a regular carbon layer [16,25,26,27,28,29,30,39,40]. The inner surface, shown in Figure 6d, has more holes and microspheres.…”

“…The inner surface, shown in Figure 6d, has more holes and microspheres. This phenomenon may be due to a large amount of inert gases, such as carbon dioxide, being decomposed by HSPCTP [15,16,25,26,27,28,29,30,39,40].…”

“…However, silicon-containing cyclotriphosphazene flame retardants have scarcely been reported. He et.al [30] employed hydroxyl silicone oil to replace chlorine on HCCP (SCP), however, the chlorine was not completely replaced. Furthermore, a relatively larger amount of flame retardant (7.5%) was required to achieve the UL94 V-0 flame-retardant rating for PC materials.…”

One-Step Synthesis of Highly Efficient Oligo(phenylphosphonic Dihydroxypropyl Silicone Oil) Flame Retardant for Polycarbonate

“…The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for the EP/DOPO/PSiN system holds a more cohesive and dense char structure when compared to the pure EP and EP/DOPO systems. Many works have been performed on the compounds containing two or more flame-retardant elements including phosphorus, nitrogen, sulfur, and boron [21][22][23][24][25]. However, few studies have reported on flame retardants containing both phosphorus and silicon, and the weight ratios of the flame retardants were too high [26,27].…”