Synthesis of surface-active quaternary amino polyfluorosiloxanes

We report synthesis of surface-active quaternary amino polyfluorosiloxanes. Hydrosilation of silanic hydrogen containing polyfluorosiloxanes with olefinic epoxides, in the presence of a platinum–divinyltetramethyldisiloxane complex gave epoxy polyfluorosiloxanes. These, on further reaction with various amines followed by quaternization, gave quaternary amino polyfluorosiloxanes. The quaternary amino polyfluorosiloxanes reduce surface tension of water to 25 mN/m² at a 25-millimolar concentration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1700–1708, 2000     

Hydrofluoroether electrolytes for lithium-ion batteries: Reduced gas decomposition and nonflammable

The optimum combination of high energy density at the desired power sets lithium-ion battery technology apart from the other well known secondary battery chemistries. However, this is besieged by thermal instability of the electrolyte. This “Achilles heel” still remains a significant safety issue and unless this propensity is improved the promise of widespread adoption of Li-ion batteries for Transportation application may not be realized. With this in mind we launched a systematic study to evaluate fluoro solvents that are known to be nonflammable, for thermal and electrochemical performances. We investigated hydro-fluoro-ethers (HFE) (1) 2-trifluoromethyl-3-methoxyperfluoropentane {TMMP} and (2) 2-trifluoro-2-fluoro-3-difluoropropoxy-3-difluoro-4-fluoro-5-trifluoropentane {TPTP} in Sandia-built cells. Thermal properties under near abuse conditions that exist in thermal runaway environment and the electrochemical characteristics for these electrolytes were measured. In the thermal ramp (TR) measurement, EC:DEC:TPTP-1 M LiBETI (or TFSI or LiPF₆) electrolytes exhibited no ignition/fire. Similar behavior was observed for the EC:DEC:TMMP-1 M LiBETI. Further, in ARC studies the HFE electrolytes generated less gas by 50% compared to the EC:EMC-1.2 M LiPF₆ {CAR-1} electrolyte. Although in all cases the HFEs generated less gas, the onset of gas generation appears to depend on the salt. For the LiBETI and TFSI containing HFEs the onset is pushed out by ∼80 °C and for the LiPF₆ the onset is comparable to that of the CAR-1. The solution ionic conductivity of these HFE electrolytes was lower (4-5 times) than that of the CAR-1 electrolyte however, the electrochemical performance was comparable. For example, full cells in 2032 type coin cells containing LiMN_0.33Ni_0.33Co_0.33O₂ cathode and carbon anode showed around 5 mA h capacity and the computed specific capacity was ∼154 mA h for all the electrolytes. In half-cells against lithium the cathode and anode gave specific capacity on the order of 170 mA h and 340 mA h respectively. These electrolytes when tested in 18,650 cells containing the above cathode and anode also showed comparable capacity. Further, the voltage stability window was not compromised by the HFEs. ARC measurements on 18,650 full cells showed less gas generation for the HFE electrolytes compared to CAR-1 electrolyte.     

温度对PTFE膜材料力学性能的影响

对聚四氟乙烯(PTFE)膜材进行了9种温度(-20,-10,0,10,23,40,50,60,70℃)下的单轴单调和循环拉伸试验,得到了膜材力学参数的变化规律.结果表明:随着温度的增加,PTFE膜材的抗拉强度逐渐减小,而断裂延伸率和弹性模量逐渐增大;随着循环次数的增加,PTFE膜材滞回曲线趋于稳定,残余应变趋于常数.在试验研究的基础上,提出了PTFE膜材强度的温度影响系数,为PTFE膜材强度设计分项系数的取值提供了依据.     

The One‐Pot Wittig Reaction: A Facile Synthesis of α,β‐Unsaturated Esters and Nitriles by Using Nanocrystalline Magnesium Oxide

Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions.     

并用比对氟橡胶/氟硅橡胶并用胶性能的影响

将氟橡胶与氟硅橡胶/硅橡胶混炼胶并用,制备氟橡胶/氟硅橡胶并用胶,研究氟橡胶/氟硅橡胶并用比对并用胶性能的影响。结果表明:随着氟硅橡胶用量增大,并用胶的脆性温度降低,耐低温性能明显提高;当氟橡胶/氟硅橡胶并用比为8/2时,并用胶的微观结构未出现明显分层现象,物理性能较好。     

我国氟树脂的加工应用现状

介绍国产氟树脂主要品种，分析国产氟树脂在加工中存在的质量问题、原因及应用现状，提出一些尚待开发的氟树脂加工新工艺。     

氟橡胶密封件的研制

对氟橡胶、氟硅橡胶及两胶并用进行了配方、工艺试验，优选出最佳配方，氟橡胶密封件耐苯、耐油性能优异，适于作油制煤气控制阀密封件。     

水蒸汽对四丙氟橡胶性能的影响

就四丙氟橡胶ＴＰ－２／ＤＣＰ－ＴＡＩＣ体系做了耐２８０℃×４８０ｈ水蒸汽实验，结果表明，其硫化胶的性能保持率较高，体积变化在６０％～３０％。     

我国氟、硅橡胶工业发展现状及建议

介绍了氟、硅橡胶的性能和应用,对我国氟、硅橡胶工业发展现状进行了概述,提出了存在的问题及发展建议。指出:针对氟橡胶产品品种少、加工手段落后的现状应加大新产品的开发力度;加强应用产品的研究,努力形成配套供货的优势;加强技术服务和技术合作,积极开展应用配方研究。对硅橡胶应开发和建立具有经济规模的生胶及混炼胶装置,开发混炼胶系列品种和高品质品种。     

常温固化氟涂料的制备、性能及发展（下）

常温固化氟涂料具有卓越的性能，本文着重介绍了常温固化氟涂料实现的途径，性能，制备及发展概况。