Answer: there are several reasons for uneven thickness of non-woven fabrics under the same processing conditions:
(1) Inhomogeneous blending of low melting point fibers and conventional fibers: different fibers have different cohesive forces. Generally speaking, low melting point fibers have greater cohesive forces than conventional fibers and are less likely to be dispersed. For example, Japan 4080, Korea 4080, South Asia 4080 or Far East 4080 have different cohesive forces, if low melting point. The fibers are unevenly dispersed and the low melting point fibers are less abundant because they can not form enough network structure. The nonwoven fabrics are thinner and thicker than those where the low melting point fibers are more abundant.
(2) Incomplete melting of low melting point fibers: incomplete melting of low melting point fibers is mainly due to insufficient temperature. For non-woven fabrics with low base weight, the problem of insufficient temperature is usually not easy to occur, but special attention should be paid to products with high base weight and high thickness. Non-woven fabrics located at the edge are usually thicker because they have enough heat, and are located in the middle of the non-woven fabrics because the heat is easily insufficient to form a thinner non-woven fabric.
(3) High shrinkage of fibers: whether conventional fibers or low melting point fibers, if the hot air shrinkage of fibers is on the high side, non-woven fabrics during the production process because of shrinkage problems are easy to produce uneven thickness.
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