Preparation Of The Single P-N Intumescent Flame Retardant And Their Flame Retardance Research In Rigid Polyurethane Foams

Since the advent of rigid polyurethane foams (RPUF), they are used in civil and military fields widely due to their excellent properties. However, the RPUF is very flammable, which threatens people’s life and the property security seriously. Currently, the main flame retardants for RPUF are the compounds containing halogen which endow the RPUF excellent flame retardation. But when burning, these kinds of retardants release a lot of toxic gases, which pollutes environment, erodes instruments, and damages people’s health. So the halogen-free flame retardant additives which show good flame retardant efficiency and hardly pollute environment are particularly needed. Mixed intumescent flame retardants have been widely utilized in the flame retardation of RPUF and manifested good efficiency, however, they are confronted with the problems of water solubility. Furthermore, they are not compatible with the RPUF matrix, which weakens the mechanical properties of the RPUF. The single intumescent flame retardant which chemically combines acid source, carbonization agent, and blowing agent into one molecule have been developed and proved to excellent flame-retardance and water resistance additives. And these flame retardants have little damage for the mechanical properties of polymeric matrix. It solves the problem of mixed intumescent flame retardants.Based on the superior performance of the single intumescent flame retardant, the three novel flame retardant, toluidine spirocyclic pentaerythritol bisphosphonate (IFRA), poly ethanediamine spirocyclic pentaerythritol bisphosphonate (IFRB),2,2-diethyl-1,3-propan ediol phosphoryl melamine (IFRC) were prepared by molecular design and used as a flame-retardant additive for RPUF. The effects of these compounds on the flame retardancy and water resistance and the influence on the compressive strength of the RPUF were examined, the flame retardant mechanism were also studied. The main contents are given as follows: 1. A novel flame retardant IFRA was synthesized with spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) and toluidine as raw materials, and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and elemental analysis (EA). The best preparation process was obtained, too. Thermogravimetic analysis (TGA) results show that IFRA has excellent charforming ablity, and the IFRA degrades earlier than RPUF and forms intumescent chars before RPUF decomposes, which indicates IFRA is a suitable flame retardant for RPUF matrix. Halogen-free flame retardant RPUF with different amount of IFRA were prepared successfully by using IFRA as a flame retardant. The scanning electron microscopy (SEM) and compressive strength test indicate IFRA exhibited favorable compatibility with RPUF and negligible negative influence on the mechanical properties of RPUF. The flame retardance of the flame retardant rigid polyurethane foam (RPUF-IFRA) was studied by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test (CCT). The results show when the content of IFRA is30pph, the LOI of RPUF-IFRA(30) could reach26.5%, and a UL-94V-0rating is achieved. The peak heat release rate (PHRR) and total heat release (THR) decrease by11.5%and13.1%, respectively, RPUF-IFRA (30) could obtain excellent flame retardance. Furthermore, the RPUF-IFRA(30) exhibites an outstanding water resistance that the LOI could still reach26.0%and obtain UL-94V-0rating after soaking in hot water for168h.2. The flame retardant IFRB was prepared with SPDPC and ethanediamine as raw materials, and characterized by FTIR, NMR and EA. The preparation method of IFRB was improved by changing the reaction conditions, and the reaction yield increased by20.4%. TGA indicates that IFRB degrades earlier than RPUF and formes intumescent chars before RPUF decomposes; it is a suitable flame retardant for RPUF. The high char weight indicates that IFRB is an efficient charforming agent. The flame retardant RPUF was prepared by using IFRB as a flame retardant. The SEM and compressive strength test show IFRB exhibited favorable compatibility with RPUF and small influence on the mechanical properties of RPUF. The flame retardance of the flame retardant rigid polyurethane foam (RPUF-IFRB) was studied by LOI, UL-94test and CCT. The results show when the content of IFRB is25pph, the LOI of RPUF-IFRB (25) can reach27.0%, and a UL-94V-0rating is achieved. The PHRR and THR decrease by20.7%and27.3%, respectively. The RPUF-IFRB has excellent water resistance that the LOI could still26.0%and obtain UL-94V-0rating after soaking in hot water for168h.3. A novel flame retardant IFRC was prepared with DPPC and melamine as raw materials, and characterized by FTIR, NMR and EA. The best preparation process of IFRC was obtained by changing solvent type, reaction temperature and reaction time. TGA results shows that IFRC is a more efficient charforming agent, IFRC degrades earlier than RPUF and forms intumescent chars before RPUF decomposes, it is a suitable flame retardant for RPUF. Flame retardant RPUF with different amount of IFRC were prepared. The SEM and compressive strength test show IFRC exhibited favorable compatibility with RPUF and lesser negative influence on the mechanical properties of RPUF. The flame retardance of the flame retardant rigid polyurethane foam (RPUF-IFRC) was test by LOI, UL-94test and CCT, the results showed when the content of IFRC was25pph, the LOI of RPUF-IFRC(25) could reach29.5%, and UL-94V-0rating is achieved. The PHRR and THR decrease by50.4%and37.8%, respectively. The RPUF-IFRC(25) has an outstanding water resistance that the LOI can still reach28.5%and obtain a UL-94V-0rating after soaking in hot water for168h.4. The flame retardant mechanism was studied of IFRA, IFRB and IFRC by TGA, SEM and FTIR. The results show the charforming reaction of flame retardant RPUF can been promoted when flame retardants are added into RPUF matrix, and the more intumescent and compact chars can be formed on the surface of flame retardant RPUF, which is a critical factor for protecting the substrate material from burning. The flame retardance of the flame retardant make effect in RPUF through solid phase flame retardant mechanism.5. The flame retardance of IFRA, IFRB and IFRC were compared and the reason is analysised. The results show the charforming performance and quality of char layer of flame retardant are more excellent, the flame retardance of flame retardant is more superior. Furthermore, the structure of IFRA, IFRB and IFRC was contrasted. The results show the flame retardance can be improved with synergistic effect between blowing agent and acid source through increasing the proportion of N/P.