The effect of plasticizer (polydimethylsiloxanol) and neat (SiO2) or modified (having amine functional groups) silica (A-SiO2) on morphology, thermal, mechanical, and rheological properties of PLA/TPS blends compatibilized by maleated PLA (MPLA) was investigated. Toughened PLA/MPLA/TPS (60/10/30) blend containing 3 wt.% of plasticizer and various contents (1, 3, or 5 wt.%) of silica were prepared in a corotating twin-screw extruder. From SEM, it is clear that plasticized PLA/MPLA/TPS blend continuous porous structure is highly related to the silica content and its functionality. The results indicate that polydimethylsiloxanol enhances ductility and the initial thermal stability of the plasticized blend. DSC and DMTA analyses show that nucleation ability and reinforcing effect of A-SiO2on plasticized blend crystallization are much better than those of SiO2. Silica practically had no effect on the thermo-oxidative degradation. However, the composites with A-SiO2had better thermal stability than those with SiO2. Moreover, silica significantly improved the elongation at break.
Potato thermoplastic starch (TPS) containing 1 wt.% of pure halloysite (HNT), glycerol-modified halloysite (G-HNT) or polyester plasticizer-modified halloysite (PP-HNT) was prepared by melt-extrusion. Halloysites were characterized by FTIR, SEM, TGA, and DSC. Interactions between TPS and halloysites were studied by FTIR, SEM, and DMTA. The Vicat softening temperature, tensile, and flexural properties were also determined. FTIR proved the interactions between halloysite and the organic compound as well as between starch, plasticizers and halloysites. Pure HNT had the best thermal stability, but PP-HNT showed better thermal stability than G-HNT. The addition of HNT and G-HNT improved the TPS’s thermal stability, as evidenced by significantly higher T5%. Modified TPS showed higher a Vicat softening point, suggesting better hot water resistance. Halloysite improved TPS stiffness due to higher storage modulus. However, TPS/PP-HNT had the lowest stiffness, and TPS/HNT the highest. Halloysite increased Tα and lowered Tβ due to its simultaneous reinforcing and plasticizing effect. TPS/HNT showed an additional β-relaxation peak, suggesting the formation of a new crystalline phase. The mechanical properties of TPS were also improved in the presence of both pure and modified halloysites.
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