No abstract

In this study, luminescence electrospun (ES) nanofibers based on ternary blends of poly(9,9-dioctylfluoreny-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/poly(methyl methacrylate) (PMMA) were prepared from chloroform solutions using a single capillary spinneret. Effects of PFO/ MEH-PPV ratio on the morphology and photophysical properties were studied while the PMMA weight percentage was fixed at 90 wt %. The morphologies of the prepared ES fibers were characterized by FE-SEM and fluorescence microscopy. The obtained fibers had diameters around a few hundred nm and pore sizes in the range of 30-35 nm. The emission colors of the PFO/MEH-PPV/PMMA blend ES fibers changed from blue, white, yellowish-green, greenish-yellow, orange, to yellow, as the MEH-PPV composition increased. In contrast, the emission colors of the corresponding spin-coated films were blue, orange, pink-red, red, and deep-red. Based on the values of solubility parameters, the PFO and MEH-PPV are miscible to each other and trapped in the PMMA matrix. Hence, energy transfer between these two polymers is possible. The smaller aggregated domains in the ES fiber compared to those of spin-coated films possibly reduce the efficiency of energy transfer, leading to different emission colors. Also, the prepared ES fibers had higher photoluminescence efficiencies than those of the spin-coated films. Pure white light-emitting fibers prepared from the PFO/MEH-PPV/ PMMA blend ratio of 9.5/0.5/90 had the Commission Internationale de L'Eclairage (CIE) coordinate of (0.33, 0.31). Our results showed that different color light-emitting ES fibers were produced through optimizing the composition of semiconducting polymer in the transparent polymer matrix. This type of ES fibers could have potential applications as new light sources or sensory materials for smart textiles.

No abstract

The surfaces of jute fibers (Corchorus capsularis L.) were processed to have different dumbbell-shaped spacing (5 mm, 10 mm, 15 mm, and 20 mm), and the physical properties of the modified surfaces of the jute fibers were evaluated in this study. The dumbbell-shaped jute fiber (DJF)-reinforced friction materials were prepared through compression mold. The friction and wear performance of the DJF were tested using a friction material tester at constant speed. The results showed that the dumbbell-shaped spacing has less influence on the friction coefficients of friction materials. The friction coefficients of DJF have bigger fluctuation compared with that of straight fiber during the temperature-increasing procedure. The wear rate of DJF with dumbbell-shaped spacing of 15 mm was the lowest, except for that when the temperatures were about 200-250 C. Morphologies of wear surfaces of DJF were observed using scanning electron microscopy and the friction characteristics were analyzed. The results showed that reinforced with DJFs in the friction materials can reduce the specific wear rate and the variation in friction coefficient compared with that of straight jute fibers.

No abstract

Zeolitic imidazolate framework-8 (ZIF-8) was synthesized at room temperature, and then added with expandable graphite (EG) to polyurethane elastomer (PUE) to study their flame retardancy and smoke suppression of PUE. The results showed that when the total flame retardant was 3 wt % and the ratio of ZIF-8 and EG was 1:3, it had the best effect on the flame retardancy and smoke suppression of PUE. Compared with pure PUE, the peak heat release rate, the total heat release, and the maximum smoke density values of Z1E3 decreased by 83.4, 42.6, and 22.4%, respectively. Moreover, the limited oxygen index value of Z1E3 increased to 30.2% and its UL-94 vertical burning test reached V-1 rating. This was because ZIF-8 synergized with EG to make the intumescent char layer compact, resulting in improved flame retardancy and smoke suppression of PUE. The specific mechanism of flame retardancy and smoke suppression is also discussed in this article.

No abstract

No abstract