Terahertz spectroscopic estimation of crystallinity of poly(phenylene sulfide)

A sustainable and low pollutive strategy for the recycling of waste hot-gas filter bags: The development of filter reinforced epoxy composites

The fast accumulation of waste hot-gas filter bags has become a growing public concern considering its difficulty in degradation, severe pollution elicited by landfill and incineration, high energy consumption during burning or complicated recycling and low margin of regenerative products. Herein, we provide a new feasible recycling strategy by directly employing the cleaned polyphenylene sulfide (PPS) /polytetrafluoroethylene (PTFE) waste filters in their fabric state as the reinforcement of epoxy composites. Merely two layers of filters could produce composites with flexural strength and modulus sufficient for many applications and the additional carbon fiber fabric (CFF) covering could further strengthen the composites (295 to 1010 % increments). The filters also showed a bonding promotion function between CFF and polymethacrylimide foam in lightweight composites. After hydrothermal treatment, the composites reinforced by the recycled filters displayed 97.2 % and 90.9 % retention rate for flexural strength and modulus, respectively. Compared to the pure epoxy, the composites could achieve a limiting oxygen index of 27.6 %, and display 24 % decline in thermal energy release and 20.0 to 31.0 % reduction in the generation rate of combustion products, indicating strengthened flame-retardancy. With shortened processes and elevated properties of composites, the approach established for recycling waste filters in this work showed far-reaching implications in carbon emission reduction, environmental pollution diminishing and commercialization potential.

Analysis of sugars and sweeteners via terahertz time-domain spectroscopy

A THz-TDS spectrometer (terahertz time-domain spectroscopy) with ASOPS technology (asynchronous optical sampling) was employed in this study, aiming to explore the potential of the technique and to develop analytical applications for the identification of some saccharides. Analytical curves with linear responses were obtained in the saccharide concentration range from 1.7 to 11.7 (w/w). The characteristic peaks used for each sugar for univariate calibrations were fructose (1.704 THz), sucrose (1.827 THz), glucose (1.435 THz), lactose (1.373 THz), saccharin (2.664 THz), and sucralose (2.219 THz). Limits of detection around 1.0% (m/m) were obtained. Gaussian peak fitting was also employed as a tool to aid in the identification of saccharide components in mixtures and it was observed that the region between 0.5 and 2.0 THz is more adequate for such analysis since scattering is less evident. It was observed that in a mixture of sucrose, glucose and lactose (5% or 10% (m/m) each) in the range of 1.31 to 1.51 THz some sub-peaks of pure lactose and glucose can be identified.

Determination of starch crystallinity with the Fourier-transform terahertz spectrometer

We measured the terahertz (THz) spectra of native, amorphous, and dried starches derived from corn and potato using the Fourier-transform (FT) system and compared these spectra to the X-ray diffraction (XRD) patterns. Both native corn and potato starches had seven absorption peaks in the terahertz regions, but five peaks were observed in the amorphous states. While spectral changes slightly occurred in corn starch even after drying, increase and decrease in the terahertz peak intensities were obtained in potato starch during drying. Similar changes in both starches during amorphization and drying were obtained in the X-ray diffraction patterns, and the correlations were found between terahertz peaks and the X-ray signals. Since the intensity of the peak at 9.0 THz was correlated with crystallinity obtained using an X-ray diffraction (r² = 0.98), our data indicate that the Fourier-transform terahertz spectrometer can be a new analytical device to measure the starch crystallinity.