Study On Properties Of Biodegradable PBS And PLA Modified By Reactive Processing Via Vane Extruder

Biocompatible and biodegradable polymers have attracted significant attention from ecological and biomedical perspectives over the past decades because of the currently growing concerns about environmental protection and energy security. Poly(butylene succinate)(PBS) and poly(lactic acid)(PLA) are interesting biomaterial. However, compared with other conventional thermoplastic polymers, the mechanical and thermal properties of PBS and PLA are often not sufficient, which limits its industrial applications. In addation, compared with the traditional screw processing equipment, the unique advantages of vane plasticizing conveying equipment are small in size, and low energy consumption and the wide adapatability for materials processing. Therefore, this study successfully prepared a series of biodegradable PBS and PLA materials which with excellent perfornmance via vane extruder by adjusting the process parameters. The main contents and results of this paper are as follows:The effect of processing temperature, speed of vane and the effect of varied TDI-TMP prepolymer on the efficiency of the reaction between PBS and TDI-TMP prepolymer were investigated. The results indicated that the optimum reaction temperature is 120 oC and the best vane speed is 27 rad/min. What’s more, TDI-TMP prepolymer could crosslink PBS with high efficiency. The gel fraction of the crosslinked PBS increased with the content of TDI-TMP prepolymer, and the melt flow index of PBS decreased. Differential scanning calorimetry and dynamic mechanical analysis revealed that the crystallization temperature and glass transition temperature increased with the content of the TDI-TMP prepolymer, while the melting points and degree of relative crystallinity decreased. The crosslinked PBS also showed improved tensile properties, impact properties, thermal stability, and dynamic mechanical properties.The mechanical, thermal and dynamic mechanical properties of PBS crosslinked by HDIT were also investigated. And we compared the properties of PBS crosslinked by HDIT and TDITMP. The results indicated that HDIT is a batter crosslinker for PBS in our study system. Compared with that of pure PBS(32.3 MPa), the tensile strength at break of crosslinked PBS enhanced by 92.9 %, when 1.5 wt% HDIT were added to the PBS. Simultaneously, the elongation at break of the crosslinked PBS increased with the HDIT content. The crossliniked PBS exhibited elongation at break of 751.5 %, respectively, when 1.5 wt% HDIT were added to the PBS. These values were approximately 6.01 times that of pure PBS(125.2 %). However, the thermal stability of PBS crosslinked by TDI-TMP is batter than the thermal stability of PBS crosslinked by HDIT.The crosslinked PBS by HDIT was used as a toughener for PLA using a vane extruder. The phase morphology, as well as thermal and mechanical properties were studied to identify the effect of crosslinked PBS content and different gel content of crosslinked PBS on the properties of PLA/PBS blends. The notched impact strengths of the PLA/crosslinked PBS blends increased by 3.8 times compared to pure PLA, when 10.0 wt % PBS crosslinked by 1.5 wt% HDIT were added.The elastomer EBA-GMA containing epoxy groups was used as a toughener for PLA using a vane extruder. The phase morphology, rheological behavior, as well as thermal and mechanical properties were studied to identify the effect of EBA-GMA weight fraction on the properties of PLA/EBA-GMA blends. TGA revealed that the incorporation of EBA-GMA improves the thermal stability of PLA. With increasing EBA-GMA content, the crystallization temperature shifted to higher temperature, however, the degree of crystallinity of PLA increased due to the influence of processing method. Graft copolymer, resulting from the reaction between the epoxy functional groups of the EBA-GMA and the carboxyl and hydroxyl of PLA, increased the mechanical properties and the complex viscosity of PLA/EBA-GMA blends at low frequencies. The influence of annealing or not was also investigated by SEM, DSC, and mechanical test. Because of the annealing process, the cold crystallization peak disappeared and the degree of crystallinity of PLA increased, and the impact-fractured surfaces began to become fuzzy, as well as more fibrils could be clearly observed at low EBA-GMA content. The brittle fracture of the blends transformed into ductile fracture at low EBA-GMA content, too.PLA/PUEP dynamically vulcanized system was introduced using a vane extruder and studied in detail. The torque, FTIR spectrum, and gel content demonstrated that PUEP was vulcanized and that the isocyanate(-NCO) group in PUEP was successfully reacted with the-OH groups at both sides of the PLA. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized blends. The notched impact strengths of the dynamically vulcanized PLA/PUEP blends increased to 57.1 k J/m2, when 30.0 wt % PUEP were added. In addition, compared to the PLA/TPU blends, PLA/PUEP blends have a batter two-phase interface morphology and superior mechanical properties.