https://popups.uliege.be/esaform21/index.php?id=747 Publications of Auteurs Khalid Lamnawar fr 0 https://popups.uliege.be/esaform21/index.php?id=1024 The present work deals with the 3D printing of multimaterials based on PLA/PMMA multilayers directly obtained from pellets. This polymer pair was chosen for their miscibility at the melt state and synergistic properties (i.e., to improve and weather tune the temperature resistance, transparency and thermomechanical properties of their PLA-based materials). Thus, 3D-printed parts with repeating PMMA/PLA/PMMA layers in the Z building direction were successfully prepared in different numbers but maintaining the same composition. The main objective was to better understand the interface/interphase properties developed during this innovative processing. First, further physicochemical and dynamic thermomechanical characterizations were performed. Second, the effects of multi-extrusion 3D printing processing parameters on the thermal stability of PLA, PMMA and their printed specimens were analyzed by GPC. Then, the structuralrheological and mechanical properties of the multilayered systems were investigated in comparison to their equivalent blend. The effects of flow kinematics during extrusion as well as printing chamber temperature (PCT) and infill density (ID) were specifically studied and rationalized. The triggered interfaces were characterized by SEM and subjected to flexural and short-beam three-point bending experiments that proved their dramatic influence on the final mechanical properties. The ultimate aim of this study is to enable successful control of the interfaces/interphases obtained in these 3D-printed PLA/PMMA systems in comparison to other forming processes. Mon, 22 Mar 2021 11:57:27 +0100 Fri, 02 Apr 2021 16:54:56 +0200 https://popups.uliege.be/esaform21/index.php?id=1024 https://popups.uliege.be/esaform21/index.php?id=748 Polylactic acid (PLA) can be a good alternative to petroleum-based polymers thanks to its organic origin and its biodegradability. This study introduces some promising routes for enhancing the processability of PLA, which presents several challenges due mainly to the poor shear and elongation properties of this biopolymer. To our knowledge, this is the first paper dedicated to an investigation of foaming and/or blown extrusion of PLA that focuses on structural, rheological and thermomechanical properties. Two main routes were selected: (i) the modification of its structural, rheological and thermomechanical properties and (ii) blending the PLA with another ductile, thermoplastic biopolymer such as poly (butylene adipate-co-terephthalate) (PBAT) or polyamide (PA11). Various formulations of PLA with multifunctionalized epoxy, nucleating agents and plasticizer were prepared and characterized on the basis of their linear viscoelasticity and extensional properties. The balance of chain extension and branching was also investigated using solution viscosimetry, steric exclusion chromatography (SEC) and rheology (shear and elongation rheology). On one hand, a batch foaming process assisted by supercritical CO2 was carried out. The influence of the foaming parameters, the extent of chain modification and the contribution of crystallization to cell morphology were all evaluated. Based on these parameters, structures ranging from micro to macro-cellular-cell were obtained. On the other hand, the stability maps of blown extrusion for neat and modified PLA were established at different die temperatures. We succeeded in greatly enhancing the blown extrusion windows of PLA, achieving high blow-up ratio (BUR) and take-up ratio (TUR) values. We were able to demonstrate that faster kinetics of crystallization can also be reached for chain-extended and branched PLA formulated with adequate amounts of nucleating agents and plasticizers. Through this work, blown films with intriguing thermomechanical and mechanical properties were produced using an optimal formulation for PLA.  Sun, 21 Mar 2021 12:34:49 +0100 Fri, 02 Apr 2021 17:58:40 +0200 https://popups.uliege.be/esaform21/index.php?id=748 https://popups.uliege.be/esaform21/index.php?id=737 This paper deals with polyisobutylene (PIB) migration through post-consumer agricultural waste multilayer films based on four linear low-density polyethylene (LLDPE) matrices. Connections between shear, elongational rheology and tack surface properties were revealed for both model and recycled blends. The effects of aging time and temperature were investigated and rationalized, depending on the short- and long-chain branching in LLDPE matrices as well their polyethylene (PE) crystallization. Linear and nonlinear viscoelastic properties were influenced by even small amounts of PIB. This migration also influenced slippage in the steady-flow regime. Transient uniaxial extensional properties were shown to be very sensitive to the presence of PIB, which seems to hold back the PE strain hardening properties. Therefore, the axial force and the surface friction coefficient were determined and discussed in correlation with bulk rheological findings. These results help unveil new insights about the physical mechanisms governing PIB migration with or without fillers inhibiting this migration in recycled films. Sun, 21 Mar 2021 11:43:39 +0100 Mon, 12 Apr 2021 10:54:25 +0200 https://popups.uliege.be/esaform21/index.php?id=737