Improvement of compatibility and thermal stability of TPS/PLA blends with the addition of citric acid as a plasticizer

Abstract

Rad istražuje utjecaj amorfnog biorazgradivog termoplastičnog škroba (TPS) i dodatka limunske kiseline (LK) na toplinska svojstva i fazne prijelaze polilaktida (PLA) putem diferencijalne pretražne kalorimetrije (DSC) i termogravimetrijske analize (TGA). TPS/PLA mješavine sve se više proučavaju zbog njihove biorazgradljivosti i potencijala za zamjenu konvencionalnih polimernih materijala, no zahtijevaju aditive poput limunske kiseline za poboljšanje kompatibilnosti, toplinskih i mehaničkih svojstava. Rezultati DSC analize pokazuju smanjenje temperature staklastog prijelaza (Tg) pri dodavanju TPS-a i LK, čime se poboljšava mješljivost PLA i TPS mješavina. Također, dodavanje TPS-a i LK utječe na pomak temperature hladne kristalizacije (Tcc) te povećava stupanj kristalnosti (χc) PLA do optimalnog udjela LK (10 mas. %). S druge strane, veći udio LK u mješavinama PLA potiče plastifikaciju, smanjujući kristalnost PLA i utječući na njegov strukturni integritet. Termogravimetrijska analiza (TGA) otkriva da ugradnja PLA u termoplastični škrob (TPS) povećava njegovu ukupnu toplinsku stabilnost. Međutim, dok LK smanjuje upijanje vlage, ne pridonosi poboljšanju toplinske stabilnosti. Umjesto toga, čini se da je njegova uloga značajnija u modificiranju fizičkih svojstava, kao što su fleksibilnost i hidrofobnost, kroz učinke plastificiranja, što može ugroziti toplinsko ponašanje materijala. Istraživanje naglašava važnost optimizacije sastava TPS/PLA mješavina radi postizanja željenih toplinskih svojstava biorazgradljivih materijala.This paper investigates the effect of amorphous biodegradable thermoplastic starch (TPS) and the addition of citric acid (CA) on the thermal properties and phase transitions of polylactide (PLA) using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). TPS/PLA blends are increasingly being studied for their biodegradability and potential to replace conventional plastics, but they require additives such as CA to improve compatibility and thermal and mechanical properties. The results of the DSC analysis show a decrease in the glass transition temperature (Tg) upon the addition of TPS and CA, which improves the miscibility of PLA and TPS blends. Also, the addition of TPS and ca affects the shift of the cold crystallization temperature (Tcc). It increases the degree of PLA's crystallinity (χc) up to the optimal proportion of CA (10 wt. %). On the other hand, higher proportion of CA in PLA blends induces plasticization, reducing the crystallinity of PLA and impacting its structural integrity. Thermogravimetric analysis (TGA) reveals that incorporating PLA into thermoplastic starch (TPS) enhances its overall thermal stability. However, while CA reduces moisture absorption, it does not contribute to improving thermal stability. Instead, its role appears more significant in modifying physical properties, such as flexibility and hydrophobicity, through plasticization effects, which may compromise the thermal behavior of the material. The research emphasizes the importance of optimizing the composition of TPS/PLA blends in order to achieve the desired thermal properties of biodegradable materials