ИСТИНА

In this work, unoriented crystalline fibers based on poly(ε-caprolactone) (PCL) were used. PCL is a linear aliphatic, biocompatible, semi-crystalline thermoplastic polyester derived from crude oil through ring opening of ε-caprolactone monomer [1]. The PCL pellets had the following characteristics: molecular weight (Mn) of 140 kDa, polydispersity index of 1.75, glass-transition temperature of -60 oC and melting temperature of 60 оC. The fibers were obtained by the melting technology. The mechanical properties of fibers were studied using an Instron 4301 tensile machine. Fibers with a diameter of 700-750 μm were uniaxially deformed at room temperature (20-25 °C) in air and in a water-ethanol mixture with an ethanol content of 94% by weight. The stretching rate was 25%/min. It was found that the process of deformation of fibers based on PCL in a water-ethanol mixture proceeds according to the mechanism of delocalized crazing. In the presence of an active media, which reduces the interphase surface energy, the microvoids are stabilized and a porous structure permeable to liquids is developed. The water-ethanol medium, which is adsorption-active for PCL, fills and stabilizes the microvoids formed during deformation, thereby promoting the development of a network of interconnected pores permeable to the liquid throughout the bulk polymer. The formation of a fibrillar-porous structure in the sample during its uniaxial deformation in a liquid medium is confirmed by small-angle X-ray scattering data carried out in mode in situ. In the absence of the medium, the polymer is deformed with the formation of non-porous monolithic neck. The formation of a non-porous monolithic neck in air occurs at a degree of deformation of 20%. In the transition from deformation in air to deformation in a water-ethanol medium, the process of neck formation is delayed to a degree of deformation of 100%. This fact correlates well with the results obtained from the experiment on estimating the bulk porosity by changing the geometric dimensions of the PCL samples after deformation into the water-ethanol mixture. On the curve of the dependence of the volume increment on the degree of deformation, a maximum was observed with a degree of deformation of 75-100%, after which a decrease in porosity occurs and the process of neck formation begins. The material retains an open-porous structure after stretching in a liquid medium and thermal fixation at a temperature of 40 °C. This fact makes it possible to obtain functional fibrous materials based on PLC, using a simple method of impregnation with a solution of a functional additive.