Abstract
Thermoplastic starch (TPS) is in situ ring-opening polymerized with L-lactide (L-LA) and directly condensed with a poly(butylene succinate) (PBS) prepolymer in an extruder using two different production pathways to demonstrate the concept “like dissolves like” in a miscible poly(lactide)/TPS/PBS (PLA/TPS/PBS) ternary blend. The TPS crystalline pattern changes from a VH-type to an EH-type after TPS modification with a hydrophobic-PLLA segment. Heteronuclear multiple-bond correlation confirmed the successful formation of PLLA-TPS-PBS copolymers via two different in situ chemical modification pathways (i.e., (I) step-by-step modification and (II) one-pot reaction). All obtained PLLA-TPS-PBS copolymers functioned as the miscible phase, enhancing PLA/PLLA-TPS-PBS/PBS ternary blend miscibility, especially the random structural PLLA-TPS-PBS-II copolymers created in an in situ one-pot reaction. However, the PLLA-TPS-PBS-I copolymers can enhance PBS crystallization only. While the random PLLA-TPS-PBS-II copolymers exhibit a homogeneous multi-phase dispersion and crystallization acceleration in both the PLA and PBS chains. Moreover, the storage modulus level of the PLA/PLLA-TPS-PBS-II/PBS ternary blend remains high with a downward temperature shift in the glass transition region, indicating a stronger and more flexible system. The practical achievement of in situ modified TPS and, consequently, a miscible PLA/PLLA-TPS-PBS/PBS ternary blend with favorable physical properties, reveal its potential application in both compostable and food contact packaging.
Highlights
Introduction iationsIn recent years, environmental concerns have prompted important changes in governmental and institutional policies
PLA, poly(butylene succinate) (PBS), and other biodegradable resins made through reliable, industrial-scale production methods are currently used to meet these environmental policies
PLA is derived from renewable resources that has attractive properties such as clarity, high tensile strength, and approval as food contact materials
Summary
Environmental concerns have prompted important changes in governmental and institutional policies. Biodegradable plastics have been widely employed to reduce plastic waste pollution, especially in disposable packaging [1]. PLA, PBS, and other biodegradable resins made through reliable, industrial-scale production methods are currently used to meet these environmental policies. PLA is derived from renewable resources (e.g., corn, beet, and cassava) that has attractive properties such as clarity, high tensile strength, and approval as food contact materials. PBS is home-compostable, thermally stable, highly flexible with low glass transition temperature (Tg ), and has a high degree of crystallinity (40–60%). PBS is expensive and opaque with poor melting strength and a limited processing window [4,5]
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