Effects of mixing protocols on impact modified poly(lactic acid) layered silicate nanocomposites

Abstract

Poly(lactic acid)/2 wt % organomodified montmorillonite (PLA/OMMT) was toughened by an ethylene-methyl acrylateglycidyl methacrylate (E-MA-GMA) rubber. The ternary nanocomposites were prepared by melt compounding in a twin screw extruder using four different addition protocols of the components of the nanocomposite and varying the rubber content in the range of 5-20 wt %. It was found that both clay dispersion and morphology were influenced by the blending method as detected by X-ray diffraction (XRD) and observed by TEM and scanning electron microscopy (SEM). The XRD results, which were also confirmed by TEM observations, demonstrated that the OMMT dispersed better in PLA than in E-MA-GMA. All formulations exhibited intercalated/partially exfoliated structure with the best clay dispersion achieved when the clay was first mixed with PLA before the rubber was added. According to SEM, the blends were immiscible and exhibited fine dispersion of the rubber in the PLA with differences in the mean particle sizes that depended on the addition order. Balanced stiffness-toughness was observed at 10 wt % rubber content in the compounds without significant sacrifice of the strength. High impact toughness was attained when PLA was first mixed with the clay before the rubber was added, and the highest tensile toughness was obtained when PLA was first compounded with the rubber, and then clay was incorporated into the mixture. Thermal characterization by DSC confirmed the immiscibility of the blends, but in general, the thermal parameters and the degree of crystallinity of the PLA were not affected by the preparation procedure. Both the clay and the rubber decreased the crystallization temperature of the PLA by acting as nucleating agents.

Flame-retardant behavior of bi-group molecule derived from phosphaphenanthrene and triazine groups on polylactic acid

“…However, PLA is an extremely flammable material with dripping during combustion, which restrains its application in electrical fields. Therefore, the research on flame‐retardant PLA is necessary …”

Poly(lactic acid)–layered silicate nanocomposites: The effects of modifier and compatibilizer on the morphology and mechanical properties

“…Also, in the same nanocomposite, 1% decrease in tensile modulus was accompanied by a 40% decrease in tensile strength. 24 Those nanocomposites were prepared with a single OMMT type (C30B) and at a single OMMT content (2 wt %) with varying ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) copolymer content. Higher tensile strength and modulus were obtained with the composites containing OMMT, but the elongation at break of these nanocomposites was lower compared to the elongation at break of the nanocomposites containing NPCC.…”

“…Most recently, in our previous study, rubber-toughened PLA nanocomposites prepared by melt blending were investigated focusing on blending order of the components. 24 Those nanocomposites were prepared with a single OMMT type (C30B) and at a single OMMT content (2 wt %) with varying ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) copolymer content. Intercalated/exfoliated structures were obtained for rubber contents of 10 wt % and higher.…”

Single and hybrid organoclay‐filled PLA nanocomposites: Mechanical properties, viscoelastic behavior and fracture toughening mechanism

“…PLA is well known for its excessive brittleness. The improvement of the toughness of PLA without loss of other properties, such as elastic modulus or thermal stability, has been the aim of several studies 10,17,28,29 . Flexural and impact tests were performed on EPLA and PLA nanocomposites aiming to evaluate the influence of OMt's type and content on the mechanical performance of PLA nanocomposites.…”

“…PLA has processing characteristics, such as extrusion and injection molding, comparable to conventional thermoplastics, 2 and optical, thermal and mechanical properties similar to polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS) 4 ; nevertheless, it presents high brittleness, a rather low heat deflection temperature and high gas permeability, limiting its use for packaging purposes 2,5 . Many of PLA's limitations, especially mechanical ones such as excessive brittleness, low toughness and low impact resistance, have been minimized by the addition of plasticizers or flexible polymers, 6–8 organic compounds, such as ionic liquids, 9 and nanofillers, as calcium carbonate, 10 silica, 11,12 zinc oxide, 13 graphene, 14 and organoclays 12,15–17 …”