Preparation And Characterization Of Acoustic Melamine Formaldehyde Foam

Foam materials are widely used in acoustics, packaging, construction and insulation fields because of its unique three-dimensional network structure. Traditional thermoplastic foam is difficult to meet the needs of the market due to its poor thermal stability, flammability, and even some combustion will emit toxic gases. Melamine formaldehyde foam has overcome the above shortcomings, and is popular in construction, transportation, cleaning and other industries with its outstanding performance. The domestic study on melamine formaldehyde foam is in the foundation stage, some mechanisms is not clear. In this paper, the fabrication and modification of melamine formaldehyde open cell and closed cell foam was developed. The research as follows:(1)Melamine can react with formaldehyde to form melamine-formaldehyde resin under alkaline conditions. The open cell foam was obtained by heating the resin. The effect of process conditions on density was discussed. The increase of viscosity and the content of curing agent can lead to increase of foam density.The density of foam decreased with the irradiation time going. The increase of the content of foaming agent result in the reduction of density. Emulsifier can reduce the surface tension of resin. The collapse of the foam would be happen when the surface tension is too small,and it would lead to the increase of the density.The orthogonal experiment was designed to optimize the process conditions by comparing density, the noise reduction coefficient, compression strength and compression rebound rate of foam. The optimum condition of the foams was 100 mPa · s resin with 8phr emulsifier,8phr foaming agent,8phr curing agent.(2)The improvement of the elasticity of liquid membrane can lead to the formation of closed cell foam. The influence of various process conditions on density and foam structure was studied.The density decreased first and then increased with the increase of the content of curing agent. The volume contraction is more obvious with the increase of blowing agent.The optimum condition of the closed cell foam was 1500mPa · s resin with 2phr emulsifier,8phr foaming agent, 8phr curing agent. The differences between open cell and closed cell foam with similar density in acoustics and mechanical properties were studied. The sound absorption coefficient of the open cell foam increased gradually with the increase of frequency while the sound absorption coefficient of closed cell foam was first decreased and then increased. The compression strength of closed cell foam was greater than open cell foam.(3) The polyethylene glycol, poly vinyl alcohol and carboxylated nitrile latex were chosen to modify the foam.The effect of the addition of the modifier on molecular structure, pore structure,density, compressive strength and thermal stability was studied. The foam density increased and the heat resistance decreased with the addition of polyethylene glycol. Poly vinyl alcohol can improve the density and thermal stability of the foam while the compression strength was decrease.The addition of carboxyl nitrile latex decreased the viscosity and density of the foam. The compressive strength decreased first and then increased. In addition, carboxylated nitrile latex can significantly improve the sound absorption properties of foam by the happening of phase separation.