Urea-modified lignin was prepared according to the Mannich reaction and well characterized by Fourier transform infrared spectrometer, elemental ananlyses, and scanning electron microscopy (SEM). Ammonium polyphosphate (APP) and urea-modified lignin were added into poly(lactic acid) (PLA) as a novel intumescent flame-retardant (IFR) system to improve flame retardancy of PLA. The flammability of IFR-PLA composites was studied using limiting oxygen index, UL-94 vertical burning method and cone calorimeter test, and their thermal stability was evaluated by thermogravimetric analysis. The results showed that the urea-modified lignin combined with APP exhibited much better flame retardancy and thermal stability than that of the combination of virgin lignin and APP. The improvement may be attributed to the better char morphology with more phosphoric char evidenced by SEM and X-ray photoelectron spectroscopy.

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A series of polyphosphoramides with high char residues were successfully synthesized using solution polycondensation and well characterized. The thermal properties and flammability were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The evolved gases during decomposition were also analyzed using Fourier transform infrared coupled with the thermogravimetric analyzer (TG-IR) technique. The char residues of the polyphosphoramides were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopy. The results showed that polyphosphoramides with sufficient molecular weights could be obtained, having high glass transition temperatures (T g s), high thermal stabilities, as well as lower flammability depending on the diamines incorporated. The char residues showed much difference among each other. Interestingly, one sample containing an ether group in the backbone exhibited a honeycomb-like char morphology, associated with a high degree of graphitization.

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A series of polyurethane (PU) microencapsulated ammonium polyphosphate (MCAPP) were prepared by in situ polymerization from toluene‐2,4‐diisocyanate (TDI), polyethylene glycol (PEG), and pentaerythtritol (PER). And the structure was characterized by Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS). Then it chose the optimal PEG constituent to design microcapsule from scanning electron microscopy (SEM) and water solubility test. The combustion and thermal degradation behaviors of PU blended APP or MCAPP were investigated by thermogravimetric analysis (TGA), UL‐94 test, and microcombustion calorimetry. The results showed that the PU/MCAPP had better thermal stability and flame retardance, due to the stable char forming by APP and PU shell. Moreover, the water resistance of flame retarded PU composite was greatly improved. Copyright © 2009 John Wiley & Sons, Ltd.

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