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Ignition delay time (IDT) measurements for ethylene (C2H4)/nitrogen dioxide (NO2)/oxygen/argon mixtures with various blending ratios of NO2/C2H4 = 0/100, 15/85 and 50/50 were performed in a shock tube. The sensitization effect of NO2 on C2H4 ignition was investigated at pressures ranging from 1.2 to 10 atm, in the temperature range 920–1780 K, and at equivalence ratios from 0.5 to 2.0. Similar to our recent studies of NO2 effects on CH4 and C2H6 ignition (Deng et al., 2016; Deng et al., 2017), the effect of NO2 addition on measured IDTs of the unsaturated hydrocarbon C2H4 also exhibits both temperature- and pressure- dependences. NO2 addition generally promotes the reactivity of ethylene and the promotion effect is more pronounced for the mixtures with high NO2 content at higher pressures (p > 4.0 atm), at lower temperatures (T 1250 K). A detailed kinetic mechanism of C2H4/NO2 was proposed by refining critical reactions through incorporating ab-initio calculations from this study and recently published rate constant data. This mechanism is capable of reproducing the new data reported in this work and literature ones as well and has thus been used to perform sensitivity and flux analyses to kinetically interpret the interaction of NO2 with C2H4.

Dimethoxymethane (DMM, CH3OCH2OCH3), the simplest member in the class of polyoxymethylene dimethyl ethers (PODE), is regarded as a promising fuel substitute for compression ignition engines. To better understand its combustion characteristics, a comprehensive experimental and kinetic modeling study on the combustion of DMM was conducted. Ignition delay times (IDTs) of DMM/O2/Ar mixtures were measured in a shock tube at pressures from 1.0 to 10 atm, for temperatures from 1050 to 1450 K, and equivalence ratios of 0.5, 1.0 and 2.0. A predominantly ab initio derived detailed kinetic model of DMM with 121 species and 646 reactions was developed based on AramcoMech2.0 with an updated sub-mechanism of methyl formate (MF, CH3OCHO). C O bond fissions occurred in CH2 O and CH3 O moieties were demonstrated to be the dominating reaction pathways in DMM high temperature chemistry rather than the competing non-radical decomposition channels. Flux and sensitivity analyses indicated that the two C O bond fissions have a comparatively promoting effect on reactivity, while the DMM = CH3OCH2O + CH3 reaction was the dominating channel at high temperatures. The proposed model was also validated against literature experimental data, including ignition delay times, jet stirred reactor species concentrations, laminar pre-mixed flame speciation, laminar burning velocities and plug-flow reactor speciation. The good performance of the proposed model for reproducing these data revealed its ability to predict DMM combustion over a wide range of conditions. Major reaction pathways of DMM could also apply to larger PODE compounds.

To understand the effect of hydrogen addition on the auto-ignition of ammonia at high temperatures, ignition delay times of stoichiometric ammonia/hydrogen blends were measured in a shock tube at temperatures from 1020 to 1945 K, pressures of 1.2 and 10 atm, and hydrogen fractions from 0% to 70%. The measured ignition delay times were compared with seven available kinetic models. Chemical kinetic analyses were performed using both the Glarborg Model and Otomo Model to interpret the interactions between ammonia and hydrogen during the high temperature auto-ignition. Experimental results show that ammonia ignites slower than hydrogen, and hydrogen addition can reduce the ignition delay time nonlinearly. The numerical analysis identifies that 5% hydrogen addition does not significantly affect the reaction flux of ammonia at 20% fuel consumption, however, it makes the fuel H-atom abstraction reaction NH3 + H NH2 + H2 proceed in the reversed way at the initial stage of ignition, therefore generate active H radical for further chain branching and promote the reactivity.

Impact of water (H2O) vitiation on auto-ignition characteristics of kerosene/air mixtures was investigated behind the reflected shock waves covering pressures of 0.45–7.5 atm and temperatures of 900–1450 K. Arrhenius-type expressions were fitted for both mixtures with and without H2O using multiple linear regression method. Temperature- and pressure-dependences of ignition delay times were experimentally observed to be in-line with conventional hydrocarbons for all the test mixtures, but stronger pressure-dependence exhibited when presence of H2O. A four-component surrogate model fuel (25.7% n-tetradecane/23.0% 2-methylundecane/42.1% n-butylcyclohexane/9.2% n-butylbenzene) was proposed based on similarity criterion of function group. A surrogate mechanism was subsequently assembled by incorporating the modified rate rule of certain reaction class. The proposed kinetic model reproduces well the experimental observations at the entire conditions. Thermal and kinetic effects of H2O on the RP-3 reactivity were distinguished by factitiously inducing a weak collision H2O* and an inert H2O**. Results reveal that the kinetic-based promotion of H2O outweighs the thermal-based inhibition on the RP-3 reactivity at high pressures due to higher collision efficiency, which facilitates the reaction H2O2 (+M) ⟺ OH + OH (+M). However, the RP-3 reactivity is inhibited only by thermodynamics without kinetics at low pressures.

A novel method was developed for grafting poly(acrylamide) (PAAM) on to the carbon fiber (CF) surface via reversible addition–fragmentation chain transfer (RAFT) polymerization to improve the interaction between carbon fibers and epoxy matrix in the composites system. The carbon fibers were first treated with nitric acid and γ-methacryloxypropyltrimethoxy silane (KH570). Then, the PAAM was grafting onto the carbon fiber surface via RAFT polymerization. The resulted carbon fibers functionalized with PAAM (CF-PAAM) were characterized by FTIR, XPS, and TGA, and the results revealed that CF-PAAM were synthesized successfully. The introduction of PAAM chains could make the fiber surface rougher and introduce a large numbers of –NH2 groups, which can improve the interfacial adhesion in the composites. The microbond test results showed that the interfacial shear strength (IFSS) of the composites reinforced by CF-PAAM has been enhanced about 107%. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Multiwalled carbon nanotubes (MWNTs) functionalized with hyperbranched aliphatic polyamide (HAP) were prepared by polycondensation using 3-(2-aminoethylamino)propanoic acid methyl ester as monomer. The effects of HAP functionalized MWNTs (MWNT-HAP) on the properties of bismaleimide (BMI) resin were investigated. Nanocomposites based on BMI resin and different content of MWNTs were prepared. The properties of nanocomposites were characterized by TGA, DMA, flexural and impact tests. Because of the magnification of functional groups and the higher interfacial interaction between MWNT-HAP and BMI resin, the improvement of the mechanical and thermal properties of MWNT-HAP/BMI nanocomposites was more remarkable than nanocomposites containing pristine MWNTs.

In this work, polyacrylonitrile (PAN)-based carbon fibers (CF) were chemically modified with poly (glycidyl methacrylate) (PGMA) via atom transfer radical polymerization (ATRP) to improve the interaction between the CF and polymer matrix. The FT-IR, TGA, and XPS were used to determine the chemical structure of the resulting products and the quantities of PGMA chains grafted from the CF surface. The experimental results confirm that the CF surface was functionalized and glycidyl methacrylate was graft-polymerized onto the CF, and the grafting content of polymer could reach 10.2%.