A study on the effect of four thermoplastic elastomers on the properties of double-base propellants.

To improve the low-temperature mechanical properties of double-base propellants, glycidyl azide polymer-energetic thermoplastic elastomer (GAP-ETPE), polyether block copolyimide-thermoplastic elastomer (PEBA-TPE), 1,2-polybutadiene thermoplastic elastomer (PB-TPE), and ethylene oxide-tetrahydrofuran copolyester-thermoplastic elastomer (PET-TPE) were used to modify them. The effects of these four thermoplastic elastomers (TPEs) on the energy properties of double-base propellants were studied via theoretical calculations. The mechanical properties of double-base propellants at high, low, and room temperature were compared, and their thermal properties were analyzed. It was found that GAP-ETPE had a significant effect on improving the low-temperature mechanical properties of double-base propellants, with the maximum tensile strength and maximum elongation at a low temperature for the double-base propellant reaching 43.30 MPa and 6.24%, respectively.

Novel waterborne polyurethanes containing long-chain alkanes: their synthesis and application to water repellency.

In the fabric finishing field, the water repellents have received increasing interest in recent years and the development of a fluorine-free water repellent has become an attractive prospect. In this study, glyceryl monostearate-modified waterborne polyurethanes (GWPUs) with a branched structure act as water repellents, and were prepared from toluene diisocyanate, trimethylolpropane, hydroxypropyl polydimethylsiloxane, N-methyldiethanolamine, and glyceryl monostearate (GMS). The water repellency and other properties of GWPUs with different GMS content, such as water resistance, hydrophobicity, and air permeability, were studied. The results show that the GMS content for optimum water repellency was 20 wt%, which achieved the highest score (100 points) in a water repellency evaluation. As for the water repellent ability with a GMS content of 20 wt%, the water absorption of a piece of film was reduced to 7.80%, while the water contact angle of terylene coated by the water repellent rose to 148.0°.

Study on Epoxy Resin Toughened by Epoxidized Hydroxy-Terminated Polybutadiene.

Epoxy resin (EP) was toughened by epoxidized hydroxy-terminated polybutadiene (EHTPB), with the corresponding modified epoxy resin being prepared. In this paper, the microstructure of EHTPB-modified epoxy resin was characterized, while the influence of different contents of EHTPB on curing kinetics, mechanical properties, morphology, thermal properties, dynamic thermomechanical (DMA) properties and crosslink density of the modified epoxy resin were also discussed. The results showed that the EHTPB-modified epoxy resin was successfully prepared and cured completely. The activation energy (Ea) of the modified epoxy resin decreased after the addition of EHTPB. With an increase in the EHTPB content, the tensile strength (σm) of the modified epoxy resin decreased and the breaking elongation (εb) increased gradually. The initial decomposition temperature (T5%) and glass transition temperature (Tg) of the modified epoxy resin decreased with an increase in the EHTPB content. The modified epoxy resin had a rough fractured surface and the interface was blurred, presenting a ductile fracture.

[Determination of melamine in cosmetics by hydrophilic interaction chromatography-tandem mass spectrometry].

A method for the determination of melamine in cosmetics was developed by hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS). The sample was extracted in turn by aqueous solution of trichloroacetic acid and hexane, and then cleaned-up by the mixed-mode cation exchange (MCX) solid-phase extraction (SPE) cartridge. A ZIC-HILIC column was used for the separation by gradient elution, and an electrospray ion trap mass spectrometer was used in the positive ion mode. The linear range of melamine was from 0.02 mg/L to 0.5 mg/L with a correlation coefficient of 0. 998 5. The limit of detection (LOD, S/N > or =3) and limit of quantification (LOQ, S/N >10) were 5.0 microg/kg and 20.0 microg/kg, respectively. The average recoveries and the relative standard deviations ranged from 84.7% to 93.4% and from 4.5% to 8.4%, respectively, in spiked samples at the concentrations from 0.01 mg/kg to 0.1 mg/kg. The method is suitable for the determination of melamine in cosmetics.

Upstream-downstream cooperation approach in Guanting Reservoir watershed.

A case study is introduced and discussed concerning water dispute of misuse and pollution between up- and down-stream parts. The relations between water usage and local industrial structures are analyzed. Results show it is important to change industrial structures of the target region along with controlling water pollution by technical and engineering methods. Three manners of upstream-downstream cooperation are presented and discussed based on the actual conditions of Guangting Reservoir watershed. Two typical scenarios are supposed and studied along with the local plan on water resources development. The best solution for this cooperation presents a good way to help the upstream developing in a new pattern of eco-economy.