1. Introduction
Nonwoven fabric is essentially an assemblage of fibers held together by mechanical or chemical means, resulting in a mechanically stable, self-supporting, web-like structure. Melt-blown nonwovens are formed in process: convergent streams of hot air rapidly attenuate the extruded polymer streams to product extremely fine diameter fibers, and further collected to form a fine-fibered, self-bonded web [1].
Generally, the melt-blown web is highly opaque with fibers vary in diameter and random orientation in its surface. Melt-blown nonwovens are widely used in the filter material, as fibers are the main composition of melt-blown web, their diameters and distributions play an important role in determining the filtration performance. The finer of the fiber, the larger of its surface area, and thus the better filter efficiency of the web [2-3].