Reactive extrusion effects on rheological and mechanical properties of poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/epoxy chain extender blends and clay nanocomposites

Abstract

Poly(lactic acid) (PLA), a biosource, biodegradable polymer, is not suitable for some important polymer processing operations, such as film blowing and blow molding, due to its low melt strength. Moreover, while it has high tensile modulus and strength in the solid state, it exhibits low ductility. The present work is an extension of our earlier effort to improve the processability and mechanical properties of PLA by blending with poly[(butylene succinate)‐co‐adipate)] (PBSA), a biodegradable polymer with lower glass transition temperature. We evaluate the influences of incorporation of an epoxy chain extender and nanoclay on the properties of the blend. Since earlier work was conducted in a batch mixer, the influence of melt processing in the twin screw extruder and the differences between products obtained in the extruder and the batch mixer are evaluated and explained. Based on earlier work, the following PLA/PBSA blend ratios of 90:10, 80:20 and 70:30 were selected. All the samples were prepared in the twin‐screw extruder at two different screw speeds (50 and 150 rpm), to evaluate the effects of residence time and shear rates. The morphology and structure of the blends were examined using field emission scanning electron microscopy. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were used to evaluate the levels of intercalation and exfoliation in the nanocomposites. The chain extension reaction was evaluated using nuclear magnetic resonance (NMR) spectroscopy and other techniques. Rheological properties (dynamic oscillatory shear and elongational viscosity measurements) and mechanical characteristics of the pure components, blends, and nanocomposites were studied and discussed in light of the composition and morphology of the blends and the nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42664.

Mechanical evaluation of polylactic acid (PLA) based composites reinforced with different calcium phosphates

“…Particularly, the PLA-2. suggests a larger influence of the restrained polymer chains on the whole relaxation spectrum that can be achieved by a more ordered internal network [41,[45][46]. Similar effect of the compounding method was found for the PLA-HA composites (results not shown here).…”

“…Taking into account the Han plot, slope variations for composites compared to the neat matrix are related to the filler-matrix interaction and to a more complex internal structure. In addition, a shift to higher frequencies of the inflection point suggests larger energy required to modify the internal structure due to higher contact area or stronger interactions[45][46]. Li et al investigated the rheological performance of PLA reinforced with silica[46].…”

Effects of the chain‐extender content on the structure and performance of poly(lactic acid)–poly(butylene succinate)–microcrystalline cellulose composites

“…It was reported in the literature that the epoxy‐based chain extender can be involved in a chain‐extension reaction with polyester carboxyl and hydroxyl groups; this changes the rheological and mechanical properties of polyester‐related blends. In this study, we aimed to improve the compatibility between various polymers by introducing commercially epoxy‐functionalized chain extenders in PLA–PBS–MCC composites prepared through reactive extrusion.…”

Influence of Nanoparticle Pretreatment on the Thermal, Rheological and Mechanical Properties of PLA-PBSA Nanocomposites Incorporating Cellulose Nanocrystals or Montmorillonite

“…TEM micrographs support this prediction and show that the PBSA droplets are surrounded by C30B layers while the SFD-MMT layers are located inside the PBSA droplets (Figure 5). Consequently, the local concentration of the chain extender in the PLA phase of C30B-CPLA-PBSA would be more than that of SFD-CNC-CPLA-PBSA and SFD-MMT-CPLA-PBSA due to the barrier effect of clay layers [36]. More details regarding the selective localization of the nanoparticles, their surface energies and wetting coefficients in the ternary systems could be found in previous publications [6,24,36,37,38].…”