Evaluation of Functional Insoles for Protective Footwear Under Simulated Use Conditions

The objective of the work was to study the properties of functional insoles for protective footwear using an original methodology by simulating the dynamic real-life conditions. Two insole variants were examined; both are made from a three-layer composite with the middle layer being a polypropylene melt-blown nonwoven. The variants differed in terms of the presence or absence of a superabsorbent polymer (SAP) and a biocide in the middle layer. Insole samples were subjected to pressure and examined in terms of the adsorption and desorption of acidic and alkaline liquids, followed by tear strength experiments. In addition, the insoles were placed in protective footwear and the microclimate existing inside the resulting system was determined using T/RH sensors by means of three complementary methods: under controlled climatic conditions, on a thermal foot model, and on human subjects. The results clearly indicate that insoles containing SAP are more effective than those without SAP in terms of both hygienic and mechanical properties.