Impact of hydrothermal aging on microstructure transformation in Poly(L‐lactide) nonwovens under tension in condition close to a living organism

Abstract

The analysis of mechanical properties and structure of bioresorbable polymer nonwoven materials is an important area of research in the medical industry, the properties and structure of which directly affect the processes of cellular activity. In this work, the processes of reorganization of the fibrous microstructure of poly(l‐lactide) nonwoven materials under uniaxial tension in a water environment were investigated. The study which included volumetric ultrasound imaging, mechanical testing, differential scanning calorimetry, X‐ray diffraction, and melting rate measurements was the first attempt to identify correlations between the mechanical behavior of fibrous meshes and changes in the supramolecular structure of the polymer during 3 months of hydrothermal aging T = 37°C. An increase in crystallinity by 4%, a shift of glass transition temperature by 4°C, and a 2 times increase in melt flow rate under hydrolysis were indicated degradation of the amorphous phase. Local degradation of the amorphous phase of fibers led to the formation of surface cracks, an increase in the number of microcracks during hydrothermal aging resulted in a decrease in the mobility of fibers in the volume of the nonwoven material and a decrease in the elasticity of the entire nonwoven material, which was revealed using the volume ultrasound imaging and optical microphotographs.