Feng Gao,Ke Liu,Yongjun Wang,Junming Dai,Wenxing Chen,Wangyang Lu
Direct spinning of polyamide 6 (PA 6) fibers, traditionally impeded by the presence of approximately 10% residual monomer and oligomers in the polymerized form, has been made feasible through our innovative approach. Current extraction methods predominantly employ hot water to extract monomer and oligomers. However, this approach is characterized by time-consuming procedures, high energy consumption, and substantial water usage. Therefore, in this study, a straightforward falling-film devolatilization method is proposed to synchronize the liquid-phase viscosity enhancement and oligomer removal of PA 6. PA 6 industrial yarns were successfully produced using devolatilized PA 6 (D-PA 6) obtained by this method. The viscosities of D-PA 6 samples were increased from 2.5 and 2.8 to 2.8 and 3.4, their monomer contents were reduced to 0.26%, and their dimer and residual oligomer contents were reduced to 0.54 and 2.54%, respectively, with a lower removal of dimer and trimer. The process led to a wider molecular weight distribution, consistent with that typical of PA 6 spinning. The obtained PA 6 industrial yarn exhibited a high degree of crystallinity, and its orientation, thermal properties, and mechanical properties were comparable to those of conventional yarn. Although its dyeing ability was slightly compromised, this did not hinder the practical application of the PA 6 industrial yarn. The falling-film devolatilization process enables simultaneous viscosity enhancement and devolatilization without the need for hot-water extraction (24 h) and drying (24 h), drastically shortening the production time from more than 48 h to less than 10 h, thereby greatly reducing energy consumption and wastewater discharge. This study provides technical guidance for the sustainable industrial production of PA 6 industrial yarn by direct melt-spinning, which significantly reduces energy and environmental impacts while improving production efficiency.
In order to remove VOCs in paints and coatings as more as possible, photo-curable waterborne polyurethane acrylates (WPUAs) were synthesized and an easy process to obtain low VOCs and low odor by the devolatilization technology was investigated. It was found that VOCs contents and WPUAs odors were significantly reduced by using the deionized water as the devolatilization aid chemical. With the conditions that the temperature was 75 °C, vacuum degree was 0.085 MPa, and the added deionized water content was 3 wt%, the VOCs content of WPUA was 33.6 mg/g with odor level 2 after devolatilization. Moreover, in the process of devolatilization, the increasing temperature strengthened the mass transfer process, thus the removal efficiency of VOCs was improved. Comparison with the WPUA coatings without devolatilization, the photo-cured films of deodorized WPUA coatings showed good thermal stability and excellent mechanical properties due to most of the solvents and small molecular impurities were removed. The WPUA coatings with low VOCs not only reduced environmental pollution, but also improved their coatings quality. At the same time, the devolatilization technology had the characteristics of simplicity and efficiency. Therefore, it was suitable for industrial production of organic photo-curable coatings in order to protect both environment and people's health as much as possible.
Jiacong Chen,Ming Zhao,Saleem Nawaz Khan,Yang Liu,Sheng Zhao,Weiguo Dong,Qingbin Song,Chao Wang
In recent years, biomass oxy-fuel gasification has prompted increased interest for its ability to produce a gas with low tar content and to assist in carbon reduction. It is noteworthy that the type of atmosphere is a crucial factor influencing the devolatilization process in biomass gasification and the specific mechanisms by which an oxy-fuel atmosphere influences the devolatilization process remain inadequately explored. This work aimed to investigate the effect of various reaction atmospheres on devolatilization behavior, reaction kinetics, intermediate product formation, and biochar functional groups (BFGs) evolution. In comparison to an inert atmosphere, the oxy-fuel atmosphere facilitated the release of volatiles, and enhanced energy self-sustainability within the devolatilization system. The presence of O 2 and CO 2 promoted the generation of potential anhydrosugars while suppressing the formation of phenolic compounds. The synergistic effect present in the oxy-fuel atmosphere augments the exothermic effect and promotes the release of volatile and alkane gases during the devolatilization process. Furthermore, as oxygen concentrations increased in the reaction atmosphere, the sequential response of BFGs primarily followed the order: C-O → aromatic ring → C-OH/C–H/COO– → C=O. Moreover, advanced characterization analyses revealed that the oxy-fuel environment was more effective in promoting the aromatization and pore structure of biochar than an inert atmosphere. Collectively, these findings have substantial implications for reaction modeling in biomass fixed-bed gasification under real gas atmospheres and guide future research on tar control strategies.
危险品化学品经营许可证（带存储）