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.
Highlights
A reaction of isocyanate and polyhydric alcohol can form polyurethane (PU)
This formed a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant which was dissolved in THF, and this was followed by the addition reaction with a prepolymer to form nanocomposites
Hybrid the –OH functional group was between 3600 and 3200 cm−1 [9,10], the P–Ph was at 1442 cm−1 [17], The spectrum depicted in Figure 1 exhibits the characteristic absorption peak of DOPO-BQ; the the P=O was at 1200 cm−1, and the P–O–Ph was at −1
Summary
A reaction of isocyanate and polyhydric alcohol can form polyurethane (PU) It is a kind of polymer with high crosslinking and specific characteristics that are suitable for various types of materials [1,2,3], such as household mattresses, furniture, sealants, adhesives, leather, and various types of biomedical products [4]. Phosphate flame retardants can catalyze char formation. Both of these characteristics of phosphorus flame retardants can stop combustion [11]. The sol–gel method was used to prepare a flame retardant that contained nitrogen, phosphorus, and silicon, and combined it with PU to form a hybrid material. The thermostability of this hybrid material was measured through thermogravimetric analysis (TGA), integral procedural decomposition temperature (IPDT), and TG∆. A Raman spectrum was used to study the mechanism of flame retardancy from char analysis
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