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In this work, the synergistic effect of Nano‐ZnO and intumescent flame retardant (IFR) on polypropylene/ethylene‐propylene‐diene monomer (PP/EPDM) composites was researched using an elongational flow field. The results were then compared to shear flow field. The flame retardant mechanism was characterized using thermogravimetric‐Fourier transform infrared spectroscopy (TG‐FTIR). Furthermore, the flame retardant properties and morphologies of the composites using different flow fields were characterized using cone calorimeter (CC), limited oxygen index (LOI), vertical combustion test (VCT), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicated that the mixture of 1 wt% Nano‐ZnO and 29 wt% IFR which based on the elongational flow field (VZ1) catalyzed the esterification and charring effect more efficiently than that based on the shear flow field (TZ1). The TGA indicated that VZ1 exhibited higher decomposition temperature, and resulted in more char residues than those for TZ1. Furthermore, VZ1 resulted in longer delay for the ignition, and the ignition time was 105 s longer than that for TZ1, which was the longest of all samples. The fire performance index (FPI) was the highest, while the fire growth index (FGI) was the second lowest of all the samples, and resulted in the smallest fire. The digital photos showed that the char layer of VZ1 was more compact than that of TZ1. With the proposed flame retardant exhibited better dispersion and unique "bee‐comb" microstructure in the matrix through elongational flow field, and showed better retarding characteristics than that using shear flow field. POLYM. COMPOS., 40:2819–2833, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The flammable and the mechanical effects of silica (SiO2) on the halogen-free, flame-retarded ethylene–octene copolymer (POE)/polypropylene (PP) composites were investigated. Through the thermal stability analysis and the combustion test, it was found that the SiO2 had a synergistic effect on the intumescent flame retardant (IFR), especially when the SiO2 content was 3 wt%. According to the results of mechanical properties, the tensile strength of composites increased with the rising SiO2 content and most of the impact strength is retained. The fracture morphology showed the state of SiO2/IFR particles in the POE/PP blends, which reflected that with the increasing SiO2 content and the decreasing IFR content, the aggregates became less compact and the size of aggregates became smaller. [ABSTRACT FROM PUBLISHER]

This work aimed to study, for the first time, the melt blending of poly(lactic acid) (PLA) and ethylene acrylic acid (EAA) copolymer by a novel vane extruder to toughen PLA. The phase morphologies, mechanical, and rheological properties of the PLA/EAA blends of three weight ratios (90/10, 80/20, and 70/30) were investigated. The results showed that the addition of EAA improves the toughness of PLA at the expense of the tensile strength to a certain degree and leads the transition from brittle fracture of PLA into ductile fracture. The 80/20 (w/w) PLA/EAA blend presents the maximum elongation at break (13.93%) and impact strength (3.18 kJ/m2), which is 2.2 and 1.2 times as large as those of PLA, respectively. The 90/10 and 80/20 PLA/EAA blends exhibit droplet-matrix morphologies with number average radii of 0.30-0.73 μm, whereas the 70/30 PLA/EAA blend presents an elongated co-continuous structure with large radius (2.61 μm) of EAA phase and there exists PLA droplets in EAA phase. These three blends with different phase morphologies display different characteristic linear viscoelastic properties in the low frequency region, which were investigated in terms of their complex viscosity, storage modulus, loss tangent, and Cole-Cole plots. Specially, the 80/20 PLA/EAA blend presents two circular arcs on its Cole-Cole plot. So, the longest relaxation time of the 80/20 blend was obtained from its complex viscosity imaginary part plot, and the interfacial tension between PLA and EAA, which is 4.4 mN/m, was calculated using the Palierne model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40146. [ABSTRACT FROM AUTHOR]