RESUMO
This article is devoted to the development of new photostabilizers for polylactide (PLA), a polymer that is an environmentally friendly alternative to polymers and is based on fossil raw materials. We have elucidated the role of the reaction center of two potential PLA photoprotectors: N-isobornylaniline and 2-isobornylphenol, in reactions occurring in a polymer matrix under the action of UV-C radiation. PLA samples with the photostabilizers were irradiated under a wavelength of 253.7 nm for 4, 8 and 12 h. The effectiveness of the photostabilizers was evaluated based on FTIR spectrometric data, 1H and 13C NMR, scanning electron microscopy and simultaneous thermal analysis (TG-DSC). Both stabilizers led to the protection of ester bonds between monomer units of PLA. However, 2-isobornylphenol proved to be more effective at a concentration of 0.05 wt.%, while the optimal concentration of N-isobornylaniline was 0.5 wt.% by weight. TG-DSC showed that the addition of N-isobornylaniline led to an increase in PLA resistance to thermal decomposition; the temperature of the onset of weight loss increased by 2.8 °C at 0.05 wt.% and by 8.1 °C at 0.5 wt.% of N-isobornylaniline. The photoprotector 2-isobornylphenol, on the contrary, reduced the thermal stability of PLA.
RESUMO
In this study, electrospray deposition has been used as a method to prepare lignin submicron spherical particles. Regularities of electrospraying of lignin solutions in DMSO were revealed. The influence of voltage, distance between electrodes, feed rate, temperature and concentration of lignin solution on the morphology, size and polydispersity of the obtained particles was determined. SEM, IR, TG-DSC, elemental analysis, dynamic light scattering, Zeta potential and nitrogen sorption were used to characterize the particles and to determine their properties. The aqueous colloidal solutions of the submicron particles of lignins from various plant sources were stabilized by preparing the lignin/polyvinylpyrrolidone polymeric complexes.
