Effect of Diethylene Glycol Dimethyl Ether–Diesel Blends on Tribological Characteristics of Base Oils

In this study, tribological characteristics of diethylene glycol dimethyl ether (DGM)/diethylene glycol dimethyl ether–diesel blend A (10 vol% DGM + 90 vol% diesel)/diesel were compared after being subjected to quill roller-ball friction and four-ball friction tests. The lubricity and antiwear property of blend A were worse than those of diesel, albeit considerably better than those of DGM. In addition, effects of diesel and blend A on the tribological characteristics of synthetic base oils were examined by using a four-ball friction machine and the fuzzy analytic hierarchy process: trimellitate TM128/TM320A, alkyl naphthalene AN5, and polyalphaolefin PAO6/mPAO65 exhibited good tribological characteristics, and 5 wt% blend A mixed with base oil maintained good tribological characteristics stability. Analysis results revealed that the excellent tribological characteristics of trimellitate, alkyl naphthalene, and polyalphaolefin are related to the rigid molecules of benzene rings and long-branched chains, naphthalene rings and long-branched chains, and long-branched alkanes. By the mixing of diesel or blend A, the stable lubricating oil film resisted the deterioration of the tribological characteristics.

Synthesis, characterization, and properties of thermoplastic polyimides derived from 4,4’-(hexafluoroisopropylidene)diphthalic anhydride in diethylene glycol dimethyl ether

By regulating the order of monomer addition, four kinds of copolymer polyimides (PIs) were prepared using diethylene glycol dimethyl ether (DEGDE) and N, N-dimethylacetamide (DMAc) as the solvents. The molecular weights of polyamide acids (PAAs) ranged from 3.8 × 105 to 9.2 × 105. All of the films displayed high glass transition temperatures ( Tgs) ranging from 313°C to 346°C. The polymer films show excellent thermal stabilities with 5% weight loss at temperatures of 505–524°C and char yields at 800°C were as high as 55% under nitrogen. The peel strengths of flexible copper (Cu) clads were in the range from 0.337 N cm−1 to 0.598 N cm−1. Compared to the molecular weight and peel strength of fresh PAA, those of PAAs prepared using DMAc significantly decreased after storage for 3 months at 0°C. However, when DEGDE was used as the solvent, the molecular weights of the PAAs and the thermal properties of the PIs were maintained after long storage time.