Development of Polylactic Acid Thermoplastic Starch Formulations Using Maleinized Hemp Oil as Biobased Plasticizer

Abstract

In this study, hemp seed oil was reacted with maleic anhydride in an ene reaction to obtain maleinized hemp seed oil (MHO). The use of MHO as a plasticizer and compatibilizer has been studied for polylactic acid (PLA) and thermoplastic starch (TPS) blends (80/20, respectively). By mechanical, thermal and morphological characterizations, the addition of MHO provides a dual effect, acting as plasticizer and compatibilizer between these two partially miscible biopolymers. The addition of MHO up to 7.5 phr (parts by weight of MHO per hundred parts of PLA and TPS) revealed a noticeable increase in the ductile properties, reaching an elongation at break 155% higher than the PLA/TPS blend. Furthermore, contrary to what has been observed with maleinized oils such as linseed oil, the thermal properties do not decrease significantly as a result of the plasticizing effect, due to the compatibilizing behavior of the MHO and the natural antioxidants present in the oil. Finally, a disintegration test was carried out in aerobic conditions at 58 °C, for 24 days, to demonstrate that the incorporation of the MHO, although causing a slight delay, does not impair the biodegradability of the blend, obtaining total degradation in 24 days.

Effect of surfactant content on rheological, thermal, morphological and surface properties of thermoplastic starch (TPS) and polylactic acid (PLA) blends

“…It was observed that by increasing the TPS content in the mixtures, the T 10 as T onset decreases (see Table 2 ), evidencing the hydrophilic character of the starch, and lower thermal stability compared to the samples with higher PLA content. This deterioration in thermal properties is due to the greater presence of amorphous phase of TPS after processing [ 33 ]. On the other hand, in the TPS-PLA mixtures, it is evident that the addition of Tween 20 generates an increase of 2 °C–3 °C in the starch degradation temperature (T d1 ), while the PLA degradation temperature (T d2 ) decreases around 4 °C.…”

“…and string matching [ 32 ]. In the same way, when analyzing the influence of maleinized hemp oil as a green plasticizer and/or compatibilizer in PLA/TPS blends, an increase in elongation at break and toughness values was achieved [ 33 ]. From these results it can be concluded that the maleinized oils mobilize the chains of the macromolecules and increase the free volume, as well as the degree of crystallinity.…”

Thermoplastic Starch-Based Blends with Improved Thermal and Thermomechanical Properties

“…Lactic polyacid has also been used in combination with starch, using hemp oil modified with maleic anhydride as plasticizer and compatibilizer. The added plasticizer showed improvements in the blend ductility and impact resistance [ 19 ]. Chitosan has also been used as a dispersed phase in TPS, incorporating it by thermomechanical methods and without the addition of compatibilizer.…”

Effect of Epoxidized and Maleinized Corn Oil on Properties of Polylactic Acid (PLA) and Polyhydroxybutyrate (PHB) Blend

“…The processes of the maleinization and epoxidation of vegetable oils provide greater reactivity to the oil and greater thermal stability with respect to unmodified oils. Therefore, the compatibility of the oils with PLA is improved and the plasticizing effect is increased [ 56 , 61 ]. These oils were modified from corn oil due to certain characteristics that make it interesting compared to other oils from cereals or seeds.…”