Investigation of electrospun web porosity and its statistical evaluation

Abstract

In order to objectively study the influence of various factors on the structure and porosity of the electrospun nanofibers webs and to compare the results obtained by different authors, an objective method of porosity evaluation is needed. Analysis of literature has shown that the lack of a common method for evaluating the structure of electrospun webs generates uneven results. The method of electrospun web porosity evaluation by maximum pore size in the web is presented in this article. The main investigations were done with polyamide 6 electrospun nanofibrous web. It was stated that distribution of maximum pore size in various places of the web is close to Gausian normal distribution with some positively skew. This skew is the reason why classical statistical methods cannot be used for electrospun web porosity evaluation. It was stated that for maximum pore size evaluation with reliability 99.9%, it is not possible to use 4S (4 standard deviation) rule. In the case of 100 measurements, it is necessary to use 5S rule, and in the case of 20 or 10 measurements – even 7S or 8S rule, respectively. The results show that for maximum possible pore size evaluation, it is necessary to have much more than 10 or 20 measurements (photos), and for obtaining the same reliability, it is necessary to use a higher coefficient with standard deviation, as in the classical statistical case of Gausian distribution.