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      Tailoring Heat-Seal Properties of Biodegradable Polymers through Melt Blending

      1 , , 1 , *

      International Polymer Processing

      Carl Hanser Verlag

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          In this study, we address heat-seal properties of poly (lactic acid) (PLA), blended with Poly (butylene adipate-co-terephthalate) (PBAT). The objective is to correlate blends crystalline structure and morphology to corresponding heat-seal of blends films. The SEM micrographs show a two-phase elongated morphology where stretched ellipsoids developed through elongational flow during the cast film process. To distinguish the effect of crystallization, we also prepared amorphous and crystalline PBAT films and then compared them to blends with PLA. Heat-sealed areas were created by putting film surfaces in intimate contact for 1 s at the pressure of 0.5 N/mm 2 or Pa and in the temperature range of 70 to 140 °C. Thermal analysis shows that the crystalline structure of PBAT has a significant effect on shifting its heat-seal initiation temperature (T si) up to 20 °C. Regarding the blends, incorporation of PBAT as a dispersed phase lowers T si of blend samples. Here, gradual decrease in PBAT crystallinity caused by the hindering effect of PLA rigid molecules correlates with the shift in heat-seal initiation temperature. As mentioned above, elongated disperse morphology with higher aspect ratio of the dispersed phase compared to spherical dispersed domain, is formed through film cast process. This enhances the adhesion process by providing higher contact area. The blends also show higher toughness and better puncture resistance, which is an asset for flexible packaging applications and would enhance the mechanical performance of the seal layer.

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          Most cited references 56

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          Study of biodegradable polylactide/poly(butylene adipate-co-terephthalate) blends.

          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 approximately 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 approximately 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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            A literature review of poly(lactic acid)

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              A theory crack healing in polymers


                Author and article information

                International Polymer Processing
                Carl Hanser Verlag
                17 November 2017
                : 32
                : 5
                : 606-613
                1 Chemical Engineering Department, Polytechnique Montreal, Montreal, QC, Canada
                Author notes
                [* ] Correspondence address, Mail address: Abdellah Ajji, Chemical Engineering Department, Polytechnique Montreal, Campus de l'Université de Montréal, 2900, Boul. Édouard-Montpetit, 2500, Chemin de Polytechnique, Montréal, Québec, Canada H3T 1J4, E-mail: abdellah.ajji@
                © 2017, Carl Hanser Verlag, Munich
                Page count
                References: 60, Pages: 8
                Self URI (journal page):
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