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pps proceeding
Symposium: S13 - Polymer Blends
Oral Presentation
 
 

Control of the morphology of PLA/PBAT/PA ternary blends through the use of a PBAT-b-PLA copolymer

Fu Yang (1)*, Dolci Elena (1), Phan Trang (2), Gigmes Didier (2), Peuvrel-Disdier Edith (1), Navard Patrick (1)

(1) Centre de Mise en Forme des Matériaux, MINES ParisTech - Alpes-Maritimes - France, (2) Institut de Chimie Radicalaire, Université Aix-Marseille - Bouches-du-Rhône - France

The morphology of polymer blends is controlled by the thermodynamics of the system and thus the interfacial tension between the components. We have measured the interfacial tension between different bio-based or bio-degradable polymers using methods based on the kinetics of droplet relaxation after deformation and rheological measurements in the linear viscoelastic domain using the Palierne model. Based on these measurements, a ternary blend based on polylactic acid(PLA), poly(butylene adipate-co-terephthalate)(PBAT) and a copolyamide(PA) was chosen with the objective of forming a core-shell morphology, with PA sub-inclusions encapsulated in PBAT inclusions imbedded in the PLA matrix. However, in agreement with theory, the blend depicts a semi-encapsulated morphology where PA sub-inclusions are located at the interface between PLA and PBAT. Theory is teaching that modification of one or two out of three interfacial tensions by selective compatibilization could modify the PA sub-inclusion localisation. To this end, a PBAT-b-PLA di-block copolymer was synthesized by ring opening polymerization(ROP) of D,L-lactide using commercialized PBAT(Ecoflex FBX7011, BASF) as macroinitiator. Nuclear magnetic resonance(NMR), differential scanning calorimetry(DSC), X-ray scattering and rheometry were performed to verify the existence of PBAT and PLA blocks. Liquid chromatography under limiting conditions of desorption(LC LCD) proved that covalent bonds were effectively created between these two blocks. The compatibilization effect of PBAT-b-PLA was evidenced by measuring lower interfacial tension between PBAT and PLA in presence of PBAT-b-PLA and finer morphologies of binary blends in presence of the copolymer. Regarding to its application in ternary blends, adding this di-block copolymer in PLA/PBAT/PA ternary blends modifies interfacial tension balance in the mixture such as to successfully change the morphology from semi-encapsulation to full encapsulation of PA in PBAT phase.