可水分散多异氰酸酯技术进展

可水分散多异氰酸酯作为双组分水基胶粘剂和涂料交联剂,具有使用时不会生成甲醛等有害物质的优点。简介制备方法,着重介绍国内外技术进展以及在织物整理、木材加工等方面的用途。     

环氧树脂改性双组份水性聚氨酯的研究

用甲苯二异氰酸酯(TDI)、聚醚多元醇(N210)、1,4-丁二醇(BDO)、二羟甲基丙酸(DMPA)和环氧树脂等为主要原料制备了水性聚氨酯。研究了nNCO/nOH、二羟甲基丙酸(DM PA)的用量、环氧树脂用量及固化剂用量对水性聚氨酯乳液和胶膜性能的影响,确定了较佳配方。结果表明,环氧树脂的加入显著地提高了涂膜的拉伸强度和对基体的粘合性。     

汽车隔热板双色注射模设计

对汽车隔热板进行了工艺分析,结合客户需求和制品特点,确定了制品的分型面和注塑设备,并对成型零件、浇注系统、推出机构等进行了设计,模具运行可靠,生产的制品达到了使用要求。     

环保型透明双组分改性聚氨酯胶黏剂的研究

报道了一种无溶剂、双组分、透明环氧改性聚氨酯胶黏剂,利用红外光谱法跟踪探讨了合成机理,分析了各基团之间的化学反应及其产物随时间的变化。结果表明:改性后聚氨酯的许多性能得到改进;在最佳原料配比及适宜的实验条件下,产品黏度适中,流动性好,性能稳定,储存期长;在m(合成环氧改性聚氨酯)∶m(固化剂)=5∶3的条件下,室温表干时间约45 min,剪切强度大于19 MPa,产品为韧性,耐溶剂、耐温性优良,固化过程中不起泡,用于粘接及灌封时美观。     

Dichotomous feedback: a signal sequestration-based feedback mechanism for biocontroller design

We introduce a new design framework for implementing negative feedback regulation in synthetic biology, which we term ‘dichotomous feedback’. Our approach is different from current methods, in that it sequesters existing fluxes in the process to be controlled, and in this way takes advantage of the process’s architecture to design the control law. This signal sequestration mechanism appears in many natural biological systems and can potentially be easier to realize than ‘molecular sequestration’ and other comparison motifs that are nowadays common in biomolecular feedback control design. The loop is closed by linking the strength of signal sequestration to the process output. Our feedback regulation mechanism is motivated by two-component signalling systems, where a second response regulator could be competing with the natural response regulator thus sequestering kinase activity. Here, dichotomous feedback is established by increasing the concentration of the second response regulator as the level of the output of the natural process increases. Extensive analysis demonstrates how this type of feedback shapes the signal response, attenuates intrinsic noise while increasing robustness and reducing crosstalk.     

Two-component modified polyurethane sealant for insulating glass: Design,preparation, and application

A new two-component modified polyurethane (PU) sealant was designed and synthesized for insulating glass. This sealant was designed based on a crosslinked reaction between a p-chlorophenol-blocked PU pre-polymer (Pre-polymer 2 ) in Component A and a poly-functional hyperbranched polyamine polymer (polyamide resin 300^#) in Component B. During the synthesis of Pre-polymer 2 , Fourier transform infrared spectral analysis was used to track the process, and the optimal reaction time and temperature were 1.5 h and 80 °C, in the presence of 4, 4′-diphenylmethane diisocyanate (MDI). Different curing agents also used as deblocking agents were screened and it was found that polyamide resin 300^# was a good candidate for the curing reaction. In addition, the low-temperature curing rate was also improved by using dibutyltin dilaurate (DBTDL) and organobentonite together as a composite catalyst. Finally, the prepared two-component modified PU sealant for insulating glass was successfully used in an assembly line with good performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48219.     

外墙外保温体系中抹面胶浆的防水性能研究

探索了影响外墙外保温体系中抹面胶浆防水性能的因素,如聚合物乳液的种类和用量、憎水剂、消泡剂及施工厚度等;对抹面胶浆的配方进行优化,改善其防水性能。     

LBM investigation of a Cu-water nanofluid over various configurations of pipes in the mixed convection flow

Increasing the heat capacity of heat exchangers is a crucial need for modern devices. The thermal conductivity of the usual fluids and the Nusselt (Nu) number of flows containing such fluids are two bottlenecks in the way of increasing heat delivery in the heat exchangers. For this reason, nanofluids have been introduced. The effect of utilizing a Cu-water nanofluid as a coolant of two hot pipes in a square cavity is investigated numerically with a two-component lattice Boltzmann method. The volume fraction of nanoparticles is assumed to be constant (0.03) while the Richardson (Ri) number varies from 0.02 to 20. Results show that the effectiveness of nanoparticles is better observed in the natural convection mode. However, sedimentation is also very probable at high Ri numbers, which significantly reduces the effectiveness of the nanoparticles. Configurations which produce a natural convection stream similar to the forced convection one as well as the configurations with high spacing and hence, low heat stream interactions, are the best choices for a uniform heat rate from the pipes.     

Response dynamics of phosphorelays suggest their potential utility in cell signalling

Phosphorelays are extended two-component signalling systems found in diverse bacteria, lower eukaryotes and plants. Only few of these systems are characterized, and we still lack a full understanding of their signalling abilities. Here, we aim to achieve a global understanding of phosphorelay signalling and its dynamical properties. We develop a generic model, allowing us to systematically analyse response dynamics under different assumptions. Using this model, we find that the steady-state concentration of phosphorylated protein at the final layer of a phosphorelay is a linearly increasing, but eventually saturating function of the input. In contrast, the intermediate layers can display ultrasensitivity. We find that such ultrasensitivity is a direct result of the phosphorelay biochemistry; shuttling of a single phosphate group from the first to the last layer. The response dynamics of the phosphorelay results in tolerance of cross-talk, especially when it occurs as cross-deactivation. Further, it leads to a high signal-to-noise ratio for the final layer. We find that a relay length of four, which is most commonly observed, acts as a saturating point for these dynamic properties. These findings suggest that phosphorelays could act as a mechanism to reduce noise and effects of cross-talk on the final layer of the relay and enforce its input–response relation to be linear. In addition, our analysis suggests that middle layers of phosphorelays could embed thresholds. We discuss the consequence of these findings in relation to why cells might use phosphorelays along with enzymatic kinase cascades.     

热镀用大锭锌合金生产实践

本文介绍了热镀用锌合金的生产方法,并通过配制二元合金、控制炉温、增加搅拌等方式提高了锌合金的质量,在生产实践中产品合格率由90%提高到98%,并取得了很好的经济效益。