Using maltodextrin (MD) of different dextrose equivalent (DE) values, 1,3-propanesultone, and maleic anhydride as raw materials, a novel binary modified maltodextrin (BMMD) was synthesized and further applied as a water-reducing agent. Its structure was characterized by Fourier transform infrared (FT-IR) and UV. The rheological behavior of the sample solution and strengths for concrete were also determined and the adsorption was tested by TOC. The influence of the process parameters to degree of substitution (DS) and the dosage on the fluidity of cement paste were investigated. The results show that the optimal conditions of sulfonation were the MD of DE 15, (sulfonated agent)/ (MD) of 1.4, the catalyst amount of 1% by mass MD, and the reaction time of 12 h; the optimal conditions of esterification were (esterified agent)/ (SMD) of 0.6, the reaction temperature of 90°C, and the reaction time of 4 h. The optimal dosages of sulfonated maltodextrin (SMD) and BMMD were 0.475% and 0.45%, respectively. In this dosage, the main dispersion capacity of BMMD attributes to two kinds of anchoring groups () and the appropriate molecular weight of MD.
Ablative thermal protection systems are considered to be one of the most promising means of protection for spacecraft re-entry, but challenges remain. Herein, efficient Ti-Si binary modified carbon fiber reinforced phenolic aerogel nanocomposites (C f /TS-PR) were originally designed based on a multi-stage construction strategy. The C f /TS-PR exhibited desirable mechanical strength , good thermal insulation with a minimum thermal conductivity of 0.0756 W/(m·K), remarkable thermal stability and outstanding ablation resistance, benefiting from the features of TiO 2 and the special structure of TiO 2 -SiO 2 coating. The linear ablation rates are as low as 0.004 and 0.003 mm/s at the heat flow of 1.0 and 1.5 MW/m 2 , respectively. The mass loss rates are as low as 0.006 and 0.009 g/s at the heat flow of 1.0 and 1.5 MW/m 2 , respectively. These results indicate that the C f /TS-PR nanocomposites can be a reliable thermal protection material for the future high-temperature service environment of ultra-high-speed vehicles and neutral rockets.
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