Flame Retardant Properties Of Polyurethane-Expandable Graphite-Aluminium Hydroxide Composite:Experiments And Characterization

In this dissertation, insitu generated aluminum hydroxide nanoparticles and melamine-formaldehyde resin wrapped expandable graphite were incorporated into polyurethane foams. The flame retardancy property was enhanced. Aluminum hydroxide nanoparticles were prepared by sol-gel method in polyester matrix. Expandable graphite was microencapsulated with melamine-formaldehyde resin. The flame retardant mechanism was investigated.1. Sol-gel method was used to prepare aluminum hydroxide nanoparticles. Different parameters, such as molar ratio of urea and aluminum nitrate, reaction temperature and time, the concentration of the precursor, were investigate on the relationship of parameter and particle size. Aluminum hydroxide nanoparticles were parepred in polyester matrix. Insitu generated aluminum hydroxide nanoparticles could improve the flame retardancy of polyurethane foam. With incorporation of aluminum hydroxide nanoparticles, the pore size decreased and the pore density of the foam increased. The thermal stability and dimensional stability of polyurethane foam were enhanced.2. Expandable graphite was wrapped with melamine-formaldehyde resin/aluminum hydroxyl hybrid composite. Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscope were used to characterize the structure and property. The results indicated that the thermal stability improved 50℃ with incorporation of melamine-formaldehyde resin. With incorporation of melamine-formaldehyde resin wrapped expandable graphite the flame retardancy of polyurethane foam was enhanced. The smoke density was found decreased.3. It was found that expandable graphite and aluminum hydroxide could synergistically improve the flame retardancy of polyurethane foam. The limited oxygen index reached 92.8. The degradation behavior of polyurethane foam was investigated. It was found that expandable graphite and aluminum hydroxide could accelerate the initial degradation and fluffy char was quickly generated on the surface of the composites. Thus, the degradation of the composite was slowed down and the diffusion of volatile combustible fragments to flame zone was delayed. Aluminum hydroxide could effectively induce "villi" like particles, which was useful to form a dense char. The compact char layer could effectively impede the transport of bubbles and heat.This study will provide useful direction for the preparation, property and usage of polyurethane foam. Flame retardancy polyurethane foam could be used in the building and industrial insulation materials.