A novel polyether polyol was successfully synthesized from cyclohexene oxide (CO), propylene oxide (PO), and poly(propylene glycol) 400 through ring-opening polymerization, catalyzed by double metal cyanide catalyst for the first time. Then, the obtained cyclohexane-based polyether polyol (CPOL) further reacted with 4,4 0-diphenylmethane diisocyanate to form reactive polyurethane adhesive (RPUA). The thermal properties and mechanical strength of the RPUA were characterized by differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, and lap shear strength test. It was found that with the introduction of cyclohexane units, the glass transition temperature (T g) and thermal stability of the RPUA increased about 122.3% and 3.32%, respectively. Besides, the lap shear strength of the RPUA prepared with the synthesized CPOL was 130.67% higher than the counterpart derived from conventional polyether polyol 2000. Furthermore, compared with RPUA-PPG, RPUA-CPOL also exhibited excellent lap shear strength on polycarbonate substrate even when the adhesion joints were immersed into hot water or alkaline solvent. All the above results suggest that the cyclohexane units in polyether polyol have great improvements in the thermal stability and lap shear strength of RPUA.
Advanced technology node demands new capabilities in pre-cleaning substrates of epitaxy films. In particular, cleaning carbon and native oxide on Si and SiGe surfaces are required. In this paper, we present an approach to cleaning both carbon and Si/SiGe native oxide using Previum chamber with two distinct chemistries. FTIR and SEM are used to characterize the conversion and sublimation steps of cleaning native oxide, and carbon film etch rate by hydrogen radicals is presented. The carbon cleaning and oxide cleaning capabilities are integrated in Previum chamber and significantly improved cleaning results are supported by SIMS.
Biodiesel is a renewable, biodegradable, and nontoxic fuel. At present, biodiesel is primarily produced in batch reactors in which the required energy is provided by heating accompanied by mechanical mixing. Alternatively, ultrasonic processing is an effective way to attain required mixing while providing the necessary activation energy. Biodiesel was synthesized by waste cooking oil using ultrasonication and alkali-acid catalysis method. Its structure was characterized by gas chromatograph, and the effects of various factors on transesterification rate were studied. The results show that a biodiesel yield in excess of 91% can be achieved in 30 min, at the 30Hz amplitude level, methanol/oil weight ratio of 1.3, 2% of alkaline, reaction temperature of 40-50 °C..
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