Super-Tough PLA-Based Blends with Excellent Stiffness and Greatly Improved Thermal Resistance via Interphase Engineering

Abstract

Super-tough poly(lactic acid)/polycarbonate (PLA/PC) (50/50) blends with an excellent balance of stiffness, toughness, and thermal stability were systematically designed and characterized. Poly(methyl methacrylate) (PMMA) was utilized as a novel, highly effective nonreactive interphase to promote PLA–PC phase compatibility. Partial miscibility of PMMA with both PLA and PC produced strong molecular entanglements across the PLA–PC phase boundary followed by an excellent phase adhesion. This was predicted from interfacial energy measurements and supported by dynamic mechanical thermal analysis, morphological observations, and mechanical tests. Ternary PLA/PC/PMMA blends exhibited an exceptional set of stiffness, tensile and flexural strength, tensile and flexural ductility, and thermal stability together with improved impact strength compared with neat PLA and uncompatibilized PLA/PC blends. Addition of nonreactive polybutadiene-g-styrene-co-acrylonitrile (PB-g-SAN) impact modifier to the compatibilized blend resulted in further dramatic improvements in the dispersion state of PC and PMMA phase domains followed by the development of an interconnected structure of PC, PMMA, and PB-g-SAN domains in the PLA matrix. Such a network-like morphology, with rubbery particles percolated at the interface between the dispersed structures and surrounding PLA matrix, produced a tremendous increase in impact resistance (≈700 J/m) and tensile ductility (≈200% strain) while maintaining excellent stiffness (≥2.1 GPa). The combined effects of interfacial localization of impact modifier particles, network-like morphology (extended over the entire volume of the blend), and strong phase interactions between the components (due to mutual miscibility) are described to be responsible for super-tough behavior. The role of PMMA as an efficient interphase adhesion promoter in the toughened quaternary blends is also clarified. Impact fractography revealed multiple void formations, plastic growth of microvoids, and the formation of void-fibrillar structures around as well as inside the dispersed structures as the main micromechanical deformation processes responsible for massive shear yielding and plastic deformation of blends. Blends designed in this work offer remarkable improvements in tensile and flexural ductility, impact resistance, and heat deflection temperature compared with neat PLA resin. The overall characteristics of these blend systems are comparable and/or superior to those of several commercial thermoplastic resins.

Design and Synthesis of Polystyrene-Occluded Reactive Core–Shell Particles of Natural Rubber to Balance Stiffness and Toughness in Poly(lactic acid)

“…This spatial distribution creates a network with small interparticle distances, facilitating effective overlapping of stress fields on the dispersed particles . The network-like morphology extends concentrated stress fields over the entire volume of the material, activating shear yielding mechanisms throughout the matrix . This configuration contributes to a high energy loss when stress is applied, highlighting the potential of RCS particles as efficient tougheners for PLA.…”

Wear‐ and UV‐resistant polycarbonate‐based composite films reinforced by a novel inorganic–organic hybrid filler

“…Polycarbonate (PC) serves as a thermoplastic engineering polymer and is well known for its outstanding impact strength, dimensional stability, and thermal stability. 1,2 Therefore, it finds widespread industrial applications in the fields of automotive, transportation, construction, and packaging. 3,4 Recently, PC has also been employed for the fabrication of liquid crystal materials and optical lenses, ascribed to its superior optical purity.…”

Supertoughened Polylactic Acid/Polybutylene Adipate Terephthalate Blends Compatibilized with Ethylene-Methyl Acrylate-Glycidyl Methacrylate: Morphology and Mechanical Properties by the Response Surface Methodology

“…In contrast, achieving compatibilization through the addition of a third polymeric phase requires superior miscibility and phase adhesion with each dominant phase individually, as well as the capability to create molecular entanglement at the phase boundary. Mehrabi et al 19 employed poly(methyl methacrylate) (PMMA) as an interphase modifier in a PLA/polycarbonate (PC) blend, which was capable of imparting excellent stiffness, tensile strength, and thermal stability compared to such a blend. The inclusion of an alternative copolymer, composed of reactive maleic anhydride (MA) segments and imidazolium cations, in a PLA−PBAT blend led to a notable increase (7.5 times) in ductility, while also enhancing compatibility.…”