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The pool fires that occur behind obstructions in a ventilated environment are very different from other wind-blown pool fires. The pool fire formed by fuel leakage in an engine nacelle is a typical example of a pool fire influenced by cross winds and baffles. Mastering the combustion characteristics of this type of fire is of great significance for fire prevention and control. In this study, the burning rate, flame length, and flame tilt angle of heptane pool fires behind a baffle under different cross wind velocities (ranging from 0 to 5 m/s) were experimentally investigated. Square pool fires with dimension of 8 cm and 12 cm with baffle height from 4 to 12 cm and different distances between fire and baffle (0, 20, 30 cm) were tested in a wind tunnel. The experimental results show that the burning rate increases with the increase in cross wind velocity for each baffle height. As wind velocity exceeds 2 m/s, the burning rate first decreases and then increases with the increase in baffle height. The flame length initially increases and then decreases with increasing wind velocity. The upper flame tilt angle is mainly affected by the cross wind, while the bottom flame tilt angle is influenced by the combined effects of cross wind velocity, baffle height, and distance between baffle and flame. The empirical correlations under different distances between baffle and flame, with wind velocity and baffle height accounted for, are then proposed for the dimensionless heat release rate and the flame length of heptane pool fires. [ABSTRACT FROM AUTHOR]

In this study, the in-situ compatibilization reaction between recycled acrylonitrile–butadiene–styrene copolymer (rABS) and functional styrene–ethylene–butylene–styrene block maleic anhydride (SEBS-g-MAH) was confirmed, which contributed to the toughening phenomenon of rABS, especially the notched impact strength. As mechanical test that manifested, the rABS/SEBS-g-MAH blends are stronger and more ductile than the rABS/SEBS blends. Prominently, the former has great advantage over the latter in terms of improving the impact performance. Scanning electron microscope (SEM) images showed that the compatible segments that were generated by reaction not only improve the interface adhesion of rABS/SEBS-g-MAH blends but also promote the evolution of co-continuous structures, which can be evidently observed after etching. Furthermore, the SEM micrographs of tensile fracture surfaces indicated that the formation of the co-continuous phase and the improvement of interface adhesion are the most profound reasons for the excellent tensile properties of the rABS/SEBS-g-MAH blends. The impact fracture surface revealed that two-phase interface affects crack propagation and shear yielding absorbs more impact energy than simple interface debonding does at higher deformation rates. Meanwhile, rheological analysis demonstrated that the complex viscosity of the rABS/SEBS-g-MAH (80/20 wt%) blend with a co-continuous structure exhibits a maximum positive deviation at low frequencies from the theoretical value calculated using the rule of logarithmic sum, which indicated a connection between co-continuous structure and complex viscosity. In addition, the storage modulus vs. loss modulus curves of the blends revealed that the viscoelastic behavior of rABS/SEBS-g-MAH blends is very similar to that of rABS. [ABSTRACT FROM AUTHOR]

As is an excellent bio-based polymer material, poly(lactic acid) (PLA)'s brittle nature greatly restricts its extensive applications. Herein, poly(butylene succinate) (PBS) was introduced to toughening PLA by melt blending using a self-made triple screw extruder through in situ reactive with ethylene-methyl acrylate-glycidyl methacrylate (EGMA). The effect of EGMA concentrations on the mechanical properties, morphology, interfacial compatibility of PLA/PBS blends were studied. Fourier transform infrared (FT-IR) results demonstrated that the epoxy group of EGMA reacts with the hydroxyl groups of PLA and PBS, which proved the occurrence of interfacial reactions among the tri-component. The significantly improved compatibility between PLA and PBS after EGMA incorporation was made evident by scanning electron microscope (SEM) characterization results. Meanwhile, the contact angle test predicted that the EGMA was selectively localized at the interface between PLA and PBS, and the result was verified by morphological analysis of cryofracture and etched samples. The EGMA improves the compatibility of PLA/PBS blends, and consequently leads to a significantly increased toughness with the elongation at break occurring 83 times more when 10 wt % EGMA was introduced than neat PLA, while impact strength also enhanced by twentyfold. Ultimately, the toughening mechanism of PLA based polymers was established based on the above analysis, exploring a new way for the extensive application for degradable material. [ABSTRACT FROM AUTHOR]

In this study, biodegradable poly(butylene succinate)/poly(lactic acid) (PBS/PLA) in-situ submicrofibrillar composites with various PLA content were successfully produced by a triple-screw extruder followed by a hot stretching−cold drawing−compression molding process. This study aimed to investigate the effects of dispersed PLA submicro-fibrils on the thermal, mechanical and rheological properties of PBS/PLA composites. Morphological observations demonstrated that the PLA phases are fibrillated to submicro-fibrils in the PBS/PLA composites, and all the PLA submicro-fibrils produced seem to have a uniform diameter of about 200nm. As rheological measurements revealed, at low frequencies, the storage modulus (G') of PBS/PLA composites has been increased by more than four orders of magnitude with the inclusion of high concentrations (15 wt % and 20 wt %) of PLA submicro-fibrils, which indicates a significant improvement in the elastic responses of PBS melt. Dynamic Mechanical Analysis (DMA) results showed that the glass transition temperature (Tg) of PBS phase slightly shifted to the higher temperature after the inclusion of PLA. DSC experiments proved that fiber morphology of PLA has obvious heterogeneous nucleation effect on the crystallization of PBS. The tensile properties of the PBS/PLA in-situ submicrofibrillar composites are also improved compared to neat PBS. [ABSTRACT FROM AUTHOR]