Novel Compatibilized Nylon-Based Ternary Blends with Polypropylene and Poly(lactic acid): Fractionated Crystallization Phenomena and Mechanical Performance.

This paper presents an investigation into the behavior and performance of blends of Nylon 6 (PA6), polypropylene (PP), and poly(lactic acid) (PLA), compatibilized with maleic anhydride-grafted PP (PP-g-MA). The mechanical performance of ternary PA6/PP/PLA blends was superior to that of binary PA6/PP blends because of the addition of PLA. Through blending with PLA, the tensile and flexural strength and modulus were enhanced, maintaining performance similar to that of neat PA6. Tensile performance was further enhanced through reactive compatibilization of the blends with PP-g-MA due to the improved homogeneity of the materials. Impact behavior of the blends was found to be highly dependent on morphology, and the toughening behavior was observed at certain blending ratios. In PA6/PP blends, fractionated crystallization behavior was investigated through differential scanning calorimetry, in which both PA6 and PP droplets were crystallized at supercooled states. This effect was highly influenced by the presence of the compatibilizing agent and its effect on the morphology of the dispersed phase. As the droplet size of the dispersed phase was decreased to submicron levels, the efficiency of heterogeneous nucleation was limited. Crystallization of PLA in the blend was poor, but PP-g-MA was found to have an impact on its rate of crystallization.

Novel compatibilized nylon-based ternary blends with polypropylene and poly(lactic acid): morphology evolution and rheological behaviour.

In this paper, the interaction between nylon 6 (PA6), polypropylene (PP) and poly(lactic acid) (PLA) is reported. To improve the compatibility between these immiscible polymers, a reactive compatibilization approach was used through extrusion with maleic anhydride grafted polypropylene (PP-g-MA). To further improve the compatibility of the phases, PLA was selected as a semi-polar polymer and a low molecular weight was used to assure a good droplet dispersion. All the blends were twin-screw extruded in the melt at different compositions. The morphologies of binary and ternary blends were investigated using microscopic techniques by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The PP-g-MA grafting process was observed to have a dramatic effect on the compatibility of both the binary and ternary blends and while a drastic reduction of the PP dispersed phases particle size was observed, the affinity between PLA and PP was also highlighted. The surface tension of the homopolymers and the interfacial tension of the pairs of polymers were measured to characterize the interaction at their interfaces. The interaction of PA6/PLA appeared preferable to PLA/PP, explaining the thinner dispersion obtained for PLA phase. The morphologies observed were compared to the predictions of spreading coefficient and minimum free energy models. While both models predicted the encapsulation of PP by the PLA phase, disagreeing with the morphological results, the rheological measurement gave an explanation for this phase separation. Using rheology measurements, the interaction between the phases was further investigated and the viscosity ratios were measured for the different pairs of polymers, stressing the high interaction between PA6 and PLA with and without compatibilizer. The droplet size of the dispersed phases appeared to substantially influence the chain relaxations in the melt.

Preparation and crystallization behavior of poly(ethylene 2,5-furandicarboxylate)/cellulose composites by twin screw extrusion.

Poly(ethylene 2,5-furandicarboxylate) (PEF), an emerging biobased polyester, was compounded with cellulose via twin-screw extrusion. Different extrusion parameters such as mixing time, screw speed and temperature were employed. Composite thin films containing 1, 2 and 4% cellulose w/w were prepared and compared with neat PEF films. The morphology of PEF/cellulose composites was examined by scanning electron microscopy (SEM) and the molecular weight after extrusion was controlled by means of size exclusion chromatography (SEC). The influence of the cellulose on both isothermal and non-isothermal crystallizations of PEF was investigated by differential scanning calorimetry (DSC). Crystallization is faster in presence of cellulose and the nucleating effect increases with the cellulose concentration.

Glass transition dynamics and cooperativity length of poly(ethylene 2,5-furandicarboxylate) compared to poly(ethylene terephthalate).

The glass transition of poly(ethylene 2,5-furandicarboxylate) (PEF), an emergent bio-based polyester, was investigated in comparison to one of its chemical analogues: poly(ethylene terephthalate) (PET). These investigations were conducted at different crystallinities by means of stochastic modulated differential scanning calorimetry (stochastic TMDSC) and dynamic mechanical analysis (DMA). Amorphous PEF presents a higher ΔCp at the glass transition and a broader relaxation spectrum attributed to a higher free volume. The higher Tg of PEF is then purely related to segmental mobility and specific interactions in PEF. The length of cooperative rearranging regions (CRR) was similar for both materials. Additionally, the variations of the effective activation energy E of PEF and PET at glass transitions were determined by isoconversional kinetic analysis. The rate of decrease in E was similar for the two amorphous polyesters. Upon crystallization, the glass transition of PEF is broadened but its temperature range is not increased as with PET. The creation of the rigid amorphous fraction (RAF) with crystallinity is lower in PEF than in PET. The difference in free volume also explains the lower coupling between the crystalline phase and the amorphous phase in PEF.