Both polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are biodegradable polymers. They
are thermoplastics which can be processed using most conventional polymer processing methods. PLA is high in
strength and modulus (63 MPa and 3.4 GPa, respectively) but brittle (strain at break 3.8%) while PBAT is flexible
and tough (strain at break∼710%). In view of their complementary properties, blending PLA with PBAT becomes
a natural choice to improve PLA properties without compromising its biodegradability. In this study, PLA and
PBAT were melt blended using a twin screw extruder. Melt elasticity and viscosity of the blends increased with
the concentration of PBAT. Crystallization of the PLA component, phase morphology of the blend, mechanical
properties, and toughening mechanism were investigated. The blend comprised an immiscible, two-phase system
with the PBAT evenly dispersed in the form of∼300 nm domains within the PLA matrix. The PBAT component
accelerated the crystallization rate of PLA but had little effect on its final degree of crystallinity. With the increase
in PBAT content (5-20 wt %), the blend showed decreased tensile strength and modulus; however, elongation
and toughness were dramatically increased. With the addition of PBAT, the failure mode changed from brittle
fracture of the neat PLA to ductile fracture of the blend as demonstrated by tensile test and scanning electron
microcopy (SEM) micrographs. Debonding between the PLA and PBAT domains induced large plastic deformation
in PLA matrix ligaments.
Both polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are biodegradable polymers. They
are thermoplastics which can be processed using most conventional polymer processing methods. PLA is high in
strength and modulus (63 MPa and 3.4 GPa, respectively) but brittle (strain at break 3.8%) while PBAT is flexible
and tough (strain at break∼710%). In view of their complementary properties, blending PLA with PBAT becomes
a natural choice to improve PLA properties without compromising its biodegradability. In this study, PLA and
PBAT were melt blended using a twin screw extruder. Melt elasticity and viscosity of the blends increased with
the concentration of PBAT. Crystallization of the PLA component, phase morphology of the blend, mechanical
properties, and toughening mechanism were investigated. The blend comprised an immiscible, two-phase system
with the PBAT evenly dispersed in the form of∼300 nm domains within the PLA matrix. The PBAT component
accelerated the crystallization rate of PLA but had little effect on its final degree of crystallinity. With the increase
in PBAT content (5-20 wt %), the blend showed decreased tensile strength and modulus; however, elongation
and toughness were dramatically increased. With the addition of PBAT, the failure mode changed from brittle
fracture of the neat PLA to ductile fracture of the blend as demonstrated by tensile test and scanning electron
microcopy (SEM) micrographs. Debonding between the PLA and PBAT domains induced large plastic deformation
in PLA matrix ligaments.
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