Influence of the Heat Bonding on Air Permeability

Usually, in footwear technology the upper materials are backed with heat bonding textile materials in order to increase the tensile and tear strength and the thermal resistance of the entire structure due to higher thickness. The paper studies the effects of the backing with heat bonding textiles on air permeability, an important comfort characteristic. The influence of the heat bonding with lining on the air permeability was studied using 5 types of bovine leather for upper materials and 4 types of knitted and woven fabrics for lining. The method to determine the air permeability is relatively simple and known. The air flow passing through the sample fixed on the device with the face upward is measured for certain values for the pressure difference. The conclusion drawn from the experiment is somewhat surprising: the air permeability increases with the thickness. This contradicts the general behaviour of textile structures, for which the air permeability decreases with thickness.