Surface Area
Laboratory measurement of gas molecules deposited on a fiber surface under cryogenic conditions determines the specific surface area and pore size distribution of porous materials. This method of nitrogen gas sorption is used to evaluate the surface properties of technical textiles and activated carbon fibers. By measuring the volume of gas adsorbed at different pressures, researchers calculate the internal surface structure of the sample.
The method cannot be applied to non-porous synthetic filament yarns because their surface area is too low to detect.
Pore Size
Microscopic channels in synthetic and natural fibers influence the absorption of dyes and chemical finishes. Through the use of nitrogen gas sorption, laboratories analyze whether a fiber has a mesoporous or microporous structure. This analysis helps finishes and coatings to be designed for maximum adhesion and coverage.
Adsorption Isotherm
The relationship between gas pressure and the amount of nitrogen adsorbed is plotted as an isotherm curve. Analyzing this curve reveals the shape and volume of the pores within the fiber matrix. Thus, nitrogen gas sorption provides the primary data needed to understand the filtration efficiency and protective properties of technical nonwoven fabrics.
Fiber Preparation
Preheating the sample under vacuum is required to remove any pre-existing moisture or volatile organic compounds from the pore spaces. This step ensures that the nitrogen gas has unhindered access to the fiber surface.
