Melamine formaldehyde (MF) foam is a kind of fire-retardant material, which has many excellent properties. In this paper, the effect of foaming agent on foam-cell structure of MF foam was discussed, along with the compressive property, the water absorption and its thermo gravimetric behavior as well as its fire-retardant property behaved by limited oxygen index (LOI). Through the analysis of different factors affected on MF foam and its properties we hope to get practical products with good properties. Keywords: melamine foam; foaming agent; foam-structure; thermal property; fire-retardancy;

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In order to realize the time-domain analysis based on hysteretic damping model, the frequency-independent time-domain damping model of single degree of freedom (SDOF) system is constructed. Based on the assumed relationship of vibration responses, the equivalent frequency-independent time-domain damping model in complex domain and real domain are proposed. The characteristic that the dissipated energy in each cycle is not related to the vibration frequency of external excitation is retained for the two equivalent damping models. Combined with Newmark- β method, the corresponding numerical methods are obtained. The numerical examples show that the free vibration responses are stably convergent based on equivalent damping models. The numerical results of vibration responses of SDOF system due to earthquake wave have high calculation accuracy. Compared with equivalent frequency-independent time-domain damping model in real domain, the computational accuracy of equivalent frequency-independent time-domain damping model in complex domain is higher, and the computational efficiency is lower.