Swelling kinetics and impregnation of PLA with thymol under supercritical CO2 conditions

Abstract

The present work was aimed to study swelling kinetics of polylactic acid (PLA) and its impregnation with thymol in supercritical carbon dioxide (scCO2) medium. The influences of temperature and soaking time on the swelling kinetics and impregnation yield of PLA cylindrical disc and film were investigated. Swelling experiments were performed in a high pressure view cell at 10 MPa and temperatures of 40°C, 60°C and 75°C for 2 to 24 h. On the basis of swelling kinetics, pressure of 10 MPa and temperature of 40°C were chosen for supercritical solvent impregnation (SSI) of the PLA samples during 2 to24 h. The highest swelling extent was observed for the PLA monolith after 24 h treatment with pure scCO2 (7.5%) and scCO2 with thymol (118.3%). It was shown that sufficiently high amount of thymol can be loaded into both PLA monolith and film using SSI after only 2 h (10.0% and 6.6%, respectively). Monolith and film of PLA impregnated with thymol could be suitable for active food packaging and sterile medical disposables.

Prikazana studija je namenjena ispitivanju kinetike bubrenja polilaktida (PLA) i njegovoj impregnaciji timolom u natkritičnom ugljenik(IV)-oksidu (nkCO2). Praćen je uticaj temperature i operativnog vremena na kinetiku bubrenja i prinos impregnacije PLA cilindričnog diska i filma. Eksperimenti bubrenja su izvedeni u ćeliji za rad pod visokim pritiscima na 10 MPa and 40°C, 60°C i 75°C od 2 h do 24 h. Na osnovu kinetike bubrenja, natkritična impregnacija uzoraka PLA timolom je izvedena na pritisku od 10 MPa i temperaturi od 40°C tokom 2 do 24 h. Najveći stepen bubrenja je imao PLA disk na 10 MPa i 40°C nakon 24 h (7,5%) u sistemu sa čistim nkCO2 i u sistemu sa timolom (118,3%). Pokazano je da se dovoljno visok prinos impregnacije timola može postići nakon 2 h (10,0% za disk i 6,6% za film). PLA u formi diska i filma impregnirani timolom su pogodni materijali za aktivno pakovanje hrane i za sterilni medicinski pribor.