Influence of thermochromic additive on physical properties of polylactic acid biopolymer

Termokromizem je pojav, ki povzroči spremembo barve v odvisnosti od temperature. Sprememba barve materiala se pojavi zaradi termokromnega dodatka, ki je vdelan v osnovni material. Termokromne dodatke delimo na organska barvila (levko sistem), anorganske spojine ter konjugirane polimere. V diplomskem delu smo obravnavali sistem levko barvil, ki ponuja možnost izbiranja barve materiala in prilagajanje temperature pri kateri spremenijo barvo. S pomočjo tehnologije ekstrudiranja smo pripravljeno zmes osnovnega materiala (PLA) in termokromnega dodatka pretvorili v filament in ga uporabili za izdelavo 3D tiskanih vzorcev. Vzorce in filament smo uporabili za različne analize. Opravili smo reološko karakterizacijo taline, testirali smo termične lastnosti filamentov, izvedli izpostavo vzorcev realnim pogojem, izmerili geometrijo 3D tiskanih vzorcev in določili barvne spremembe 3D tiskanih vzorcev v odvisnosti od temperature. Ugotovili smo, da na viskoznost močno vpliva temperatura tiska, geometrija vzorcev pa močno zavisi od koncentracije termokromnega dodatka. Potrdili smo, da sončna svetloba degradira vzorce in povzroči razbarvanost.Thermochromism is a phenomenon that causes a change in color as a function of temperature. The color change of the material occurs due to the thermochromic additive embedded in the base material. Thermochromic additives are divided into organic dyes (leuco system), inorganic compounds and conjugated polymers. In this research, we studied the system of leuco dyes, which offers the possibility of choosing the color of the material and adjusting the temperature at which the color change happens. Using extrusion technology, the prepared mixture of base material (PLA) and thermochromic additive was converted into filament and used to make 3D printed samples. Samples and filaments were used for various analyzes. We performed rheological characterization of the melt, tested the thermal properties of the filaments, exposed the samples to real life conditions, measured the geometry of the 3D printed samples, and determined the color changes of the 3D printed samples as a function of temperature. We found that the viscosity is strongly influenced by the printing temperature, and the geometry of the samples strongly depends on the concentration of the thermochromic additive. We confirmed that sunlight degrades the patterns and causes discoloration