Research on Toughening Polylactic Acid by an Epoxy Soybean Oil Curing Network Based on Dynamic Cross-Linking

Abstract

In this study, our primary focus was the efficient synthesis of epoxidized soybean oil and anhydrous citric acid within a polylactic acid (PLA) matrix through a ring-opening reaction catalyzed by zinc acetate. Our objective was to establish a dynamic and reversible ester exchange network. Subsequently, we introduced the cured epoxidized soybean oil network into the PLA matrix through dynamic cross-linking, aiming to enhance the compatibility of epoxidized soybean oil within the PLA matrix. This process resulted in the preparation of a series of PLA composites characterized by improved toughness. We conducted a comprehensive analysis of the influence of various carboxyl/epoxy equivalent ratios (R values) on the mechanical properties, thermal characteristics, and chemical structures of the PLA composites. Our findings demonstrated that, during the dynamic cross-linking process, both epoxidized soybean oil and citric acid underwent ring-opening reactions and chain reactions with the PLA matrix, culminating in the formation of a well-defined network cross-linking structure. These chain reactions within the system significantly enhanced the internal compatibility of the blends. Our experimental results conclusively indicated that optimal toughness was achieved when the R value was set to 0.1, with the addition of 5 parts per hundred resin (phr). This configuration resulted in an elongation at break of 315% and an impact strength of 28.5 kJ/m 2 .

Enhancement of Hydrophobic Properties in Starch‐Based Composites via Reactive Blending With Epoxidized Soybean Oil and Citric Acid

“…This behavior can be attributed to the presence of CA, which facilitates the dispersion of ESO within the starch matrix through esterification reactions with starch and oxirane ring-opening reactions of ESO, resulting in the formation of hydroxyl groups along the ESO chains [14,31]. These reactions suggest improved compatibility of the DCE phase, leading to more uniform dispersion within the starch matrix [32,33].…”

Enhancement of Hydrophobic Properties in Starch‐Based Composites via Reactive Blending With Epoxidized Soybean Oil and Citric Acid

“…This behavior can be attributed to the presence of CA, which facilitates the dispersion of ESO within the starch matrix through esterification reactions with starch and oxirane ring-opening reactions of ESO, resulting in the formation of hydroxyl groups along the ESO chains [14,31]. These reactions suggest improved compatibility of the DCE phase, leading to more uniform dispersion within the starch matrix [32,33].…”

Innovative Interfacial Compatibilization and Blowing Strategies for Advancing PLA/PBAT Blown Films: Enhancing Film Blowing Stability, Mechanical Properties, and Barrier Properties

“… , This makes it particularly unsuitable for packaging film applications requiring high flexibility. Blending with various flexible polymers such as polybutylene adipic acid/terephthalate (PBAT), polycaprolactone (PCL), poly­(butylene succinate) (PBS), propylene carbonate (PPC), epoxidized soybean oil (ESO), and polyurethane (PU) is an effective method to enhance the toughness of PLA. In practical applications, blending PLA with other biodegradable polymers serves as a simple and efficient approach to improving its toughness, while maintaining overall biodegradability.…”

Sustainable Approach to Overcome Polylactide Brittleness with Biobased Esters of Isosorbide and Fatty Acids

“…Although PLA toughness can be enhanced through copolymerization/cross-linking, , and physical blending, − plasticization remains the most widely used approach. Monomeric plasticizers, including citrates, adipates, cinnamates, tartrates, lactates, epoxidized vegetable oils, among others, offer enhanced compatibility and improved toughness, but they tend to migrate over time, leading to aging.…”

Enhancement of Hydrophobic Properties in Starch‐Based Composites via Reactive Blending With Epoxidized Soybean Oil and Citric Acid

“…This behavior can be attributed to the presence of CA, which facilitates the dispersion of ESO within the starch matrix through esterification reactions with starch and oxirane ring-opening reactions of ESO, resulting in the formation of hydroxyl groups along the ESO chains [14,31]. These reactions suggest improved compatibility of the DCE phase, leading to more uniform dispersion within the starch matrix [32,33].…”

Innovative Interfacial Compatibilization and Blowing Strategies for Advancing PLA/PBAT Blown Films: Enhancing Film Blowing Stability, Mechanical Properties, and Barrier Properties

“… , This makes it particularly unsuitable for packaging film applications requiring high flexibility. Blending with various flexible polymers such as polybutylene adipic acid/terephthalate (PBAT), polycaprolactone (PCL), poly­(butylene succinate) (PBS), propylene carbonate (PPC), epoxidized soybean oil (ESO), and polyurethane (PU) is an effective method to enhance the toughness of PLA. In practical applications, blending PLA with other biodegradable polymers serves as a simple and efficient approach to improving its toughness, while maintaining overall biodegradability.…”

Sustainable Approach to Overcome Polylactide Brittleness with Biobased Esters of Isosorbide and Fatty Acids

“…Although PLA toughness can be enhanced through copolymerization/cross-linking, , and physical blending, − plasticization remains the most widely used approach. Monomeric plasticizers, including citrates, adipates, cinnamates, tartrates, lactates, epoxidized vegetable oils, among others, offer enhanced compatibility and improved toughness, but they tend to migrate over time, leading to aging.…”

Enhancement of Hydrophobic Properties in Starch‐Based Composites via Reactive Blending With Epoxidized Soybean Oil and Citric Acid

“…This behavior can be attributed to the presence of CA, which facilitates the dispersion of ESO within the starch matrix through esterification reactions with starch and oxirane ring-opening reactions of ESO, resulting in the formation of hydroxyl groups along the ESO chains [14,31]. These reactions suggest improved compatibility of the DCE phase, leading to more uniform dispersion within the starch matrix [32,33].…”

Innovative Interfacial Compatibilization and Blowing Strategies for Advancing PLA/PBAT Blown Films: Enhancing Film Blowing Stability, Mechanical Properties, and Barrier Properties

“… , This makes it particularly unsuitable for packaging film applications requiring high flexibility. Blending with various flexible polymers such as polybutylene adipic acid/terephthalate (PBAT), polycaprolactone (PCL), poly­(butylene succinate) (PBS), propylene carbonate (PPC), epoxidized soybean oil (ESO), and polyurethane (PU) is an effective method to enhance the toughness of PLA. In practical applications, blending PLA with other biodegradable polymers serves as a simple and efficient approach to improving its toughness, while maintaining overall biodegradability.…”

Sustainable Approach to Overcome Polylactide Brittleness with Biobased Esters of Isosorbide and Fatty Acids

“…Although PLA toughness can be enhanced through copolymerization/cross-linking, , and physical blending, − plasticization remains the most widely used approach. Monomeric plasticizers, including citrates, adipates, cinnamates, tartrates, lactates, epoxidized vegetable oils, among others, offer enhanced compatibility and improved toughness, but they tend to migrate over time, leading to aging.…”