Study On The Coathanger Die Of Melt-blown Nonwoven System

Coat-hanger die is usually used as the polymer melt distributor of the melt-blown nonwoven system. The design of the coat-hanger die is of significant importance for the polymer melt distribution across the die and the quality of the final product. In the thesis, the finite element method is used to simulate the flow of the polymer fluid in the coat-hanger die of the melt-blown nonwoven system, and the coat-hanger die is optimized by means of the uniform design. The main contents are as follows.First, the 2-D finite element equations for the polymeric liquids flow in coat-hanger die are formulated by using Galerkin method with the power-law model as the constitutive equation to describe the rheological behavior of the polymeric liquids. The flow of the polymer fluid in the coat-hanger is numerically simulated, and the flow behavior of the 2% CMC/water solution in the coat-hanger die is experimentally verified by using Laser Doppler Velocimetry.Secondly, the flow of polymer fluid in the T-die and the coat-hanger die are studied by the two-dimensional finite element method. The flow pressure distribution and the flow field of the polymeric liquids in the two dies are compared. The results show that the coat-hanger die behaves better than the corresponding T-die.Thirdly, the effects of the geometrical parameters of the coat-hanger die and the property of the polymer fluid on the flow uniformity are investigated. The results show that the manifold angle and the land height are two significant factors which affect the flow distribution, and the flow distribution at the die outlet depends on the power-law index. Whether the power-law index increases or decreases, the flow distribution at the die outlet deteriorates.Finally, by means of the uniform design, the regression equations relating the uniformity index of the flow distribution with the geometrical parameters of the coat-hanger die was obtained, and the optimized parameter combination is found out. The uniformity index of the optimum coat-hanger die is over 0. 98.