Bottle-recycled polyethylene terephthalate (R-PET) fibers were fabricated by the melt spinning method. Based on characteristics of R-PET chips, this study involved a primary exploration of the spinning parameters, including spinning temperature, spinning speed and spinneret plate. The properties of R-PET and original PET (O-PET) fibers were compared using scanning electron microscopy (SEM), tensile testing, sonic orientation, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Apparent morphological observation displays an irregular cross-sectional shape and a scattered diameter distribution for R-PET fibers. Compared with O-PET fibers, R-PET fibers demonstrate a greater breaking strength and smaller elongation at break, resulting from the lower crystallinity and higher degree of orientation. Furthermore, the R-PET fibers have the same chemical structure as that of O-PET fibers demonstrated by FTIR spectroscopy, but TGA results show that thermal stability of R-PET fibers is significantly inferior to that of O-PET fibers, as a result of too many impurities and oligomers during the recycling process.

A novel double-nozzle air-jet electrospinning apparatus was developed to fabricate nanofibers on a large scale. The distribution of the electric field at different nozzle distances was simulated to analyze the jet path, productivity, and deposition area of nanofiber webs and the nanofiber morphology. Our experiments showed that the bubbles usually ruptured intermittently on the top surface of the two nozzles and the jets traveled in a straight path with a high initial velocity. A continuous and even thickness of the nanofiber webs were obtained when the nozzle distances was less than 55 mm. At nozzle distances of 55 mm, the received fibers were thin with the lowest standard deviation. Experimental parameters involving the applied voltage, collecting distance, and air flow rate were also investigated to analyze the nanofiber morphology at a nozzle distance of 55 mm. The results show that the nanofibers presented a finer and thinner diameter at an applied voltage of 36 kV, a collecting distance of 18 cm, and an air flow rate of 800 mL/min. The nanofiber production of this setup increased to nearly 70 times that with a single-needle electrospinning setup. On the basis of the principle of this air-jet electrospinning setup, various arrangements of multinozzle electrospinning setups could be designed for higher throughput of nanofibers.

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For homogeneous mixing of a polymer melt and micro/nano-inorganic particles, the researchers in our group developed a three-dimensional dynamic mixer with comprehensive effects of dispersion and distribution. To evaluate the distributive mixing effect, the expressions of diversion number and mixing degree were deduced according to the structure parameters of the mixer. To further investigate the diversion state of the melt and its velocity field in the mixer, this process was simulated with computational fluid dynamics (CFDs) software. In a pilot study, the working curves of the mixer were plotted according to the actual running state. Among other things, the pressure drop before and after mixing is discussed. This is helpful for formulating an extensional flow field and relevant to the dispersive mixing effect. Through laboratory and industrialized scale experiments it was determined with either very high or very low additions of inorganic particles, that the mixer can provide uniform and ultrafine dispersions.