Long-term weathering behavior of UV-curable clearcoats: Depth profiling of photooxidation,UVA, and HALS distributions

The long-term weathering performance of two UV-curable clearcoat systems was studied using in-plane microtomy in combination with infrared spectroscopy, UV spectroscopy, and ESR spectroscopy. Oxygen transport characteristics were also studied using the half-time method. The photooxidation versus depth profile was highly dependant on the presence of hindered amine light stabilizers (HALS) for both coating systems. Ultraviolet light absorbers (UVA) had little effect on the photooxidation profile. A photooxidation gradient was formed in both clearcoats due to a reduction in oxygen solubility when compared to standard thermoset clearcoats. This gradient was only seen in formulations not containing HALS. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Isobutane/2-butene alkylation on MCM-22 catalyst. Influence of zeolite structure and acidity on activity and selectivity

The catalytic behavior of the novel MCM-22 zeolite for the continuous alkylation of isobutane with 2-butene has been investigated at a temperature of 50°C, 2.5 MPa total pressure, and a variety of olefin space velocities. At high olefin conversions the MCM-22 zeolite showed a very high initial cracking activity attributable to strong Brønsted acid sites, as well as to the existence of strong diffusional restrictions of the TMP's (formed inside the zeolite) to exit through the channels. At short times on stream (TOS), TMP's account for ca. 40% of the C₈ fraction. The olefin conversion and the cracking activity rapidly decline with TOS, while the alkylate product became richer in dimethylhexenes, indicating a predominance of 2-butene dimerization and a loss of hydrogen transfer activity as the catalyst aged. Moreover, MCM-22 gives less TMP's than large-pore zeolites (USY, beta, mordenite), but more than the mediumpore ZSM-5 at similar 2-butene conversion. The latter catalyst was much more selective for olefin dimerization than for isobutane alkylation, presumably because formation of the bulkier TMP's was strongly impeded in its smaller pores.     

Surface properties of ZSM-5 modified by phosphorus

Phosphorus modification of ZSM-5 leads to extra framework P⁵⁺ and probably incorporation of +3 valence state of P in the framework. The resulting system has increased Brønsted acidity. Theoretical calculations also favour the postulate that phosphorus in +3 valence state can be incorporated into the lattice.     

Host Plant Volatiles Synergize Response to Sex Pheromone in Codling Moth, Cydia pomonella

Plant volatile compounds synergize attraction of codling moth males Cydia pomonella to sex pheromone (E,E)-8,10-dodecadien-1-ol (codlemone). Several apple volatiles, known to elicit a strong antennal response, were tested in a wind tunnel. Two-component blends of 1 pg/min codlemone and 100 pg/min of either racemic linalool, (E)-beta-farnesene, or (Z)-3-hexen-1-ol attracted significantly more males to the source than codlemone alone (60, 58, 56, and 37%, respectively). In comparison, a blend of codlemone and a known pheromone synergist, dodecanol, attracted 56% of the males tested. Blends of pheromone and plant volatiles in a 1:100 ratio attracted more males than 1:1 or 1:10,000 blends. Adding two or four of the most active plant compounds to codlemone did not enhance attraction over blends of codlemone plus single-plant compounds. Of the test compounds, only farnesol was attractive by itself; at a release rate of 10,000 pg/min, 16% of the males arrived at the source. However, attraction to a 1:10,000 blend of codlemone and farnesol (42%) was not significantly different from attraction to codlemone alone (37%). In contrast, a codlemone mimic, (E)-10-dodecadien-1-ol, which attracted 2% males by itself, had a strong antagonistic effect when blended in a 1:10,000 ratio with codlemone.     

Tailoring HASE rheology through polymer design: Effects of hydrophobe size, acid content, and molecular weight

Hydrophobically modified alkali-soluble emulsion (HASE) polymers are an important class of rheology modifiers for waterborne coatings applications. They are typically prepared as terpolymers by emulsion polymerization of ethyl acrylate (EA), methacrylic acid (MAA), and an associative macromonomer. The viscosity development and shear responses of HASE solutions depend on a number of factors. This article presents rheological data reflecting the impacts of three key variables: hydrophobe size, acid content, and molecular weight, on model HASE thickening and rheological performance. The relative contributions of hydrophobic association, chain expansion, and polymer chain length are discussed. In steady shear flow, all thickener solutions approached some constant low-shear viscosity at small deformation rates. At the same molar composition, larger hydrophobe size resulted in higher viscosity development and greater shear thinning behavior. The amount of acid monomer in HASE polymers can influence the balance between hydrophobic attraction and electrostatic repulsion forces. It was found that a minimum of 15 wt% MAA was required to effect dissolution and thickening of the model HASE polymers. Increasing the MAA level yielded higher zero-shear viscosity and storage modulus G’ with maximal values being obtained at 40% MAA. The molecular weight of the model thickeners was controlled by the amount of chain transfer agent (CTA) added during polymerization. When the CTA level was below 0.1 wt% based on total monomers, the polymer solutions displayed shear-thinning behavior. A small increase in CTA concentration beyond 0.1% resulted in a dramatic change to Newtonian flow, and the solution viscosity was nearly two orders of magnitude lower. The model thickeners were also tested in a vinyl acrylic architectural paint formulation. The effects of each individual factor on paint thickener efficiency, high-shear, and low-shear properties are discussed and compared with solution rheology for predictive relationships. Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 11–12, 2003, in Philadelphia, PA.     

基于嵌入式的CAN-Ethernet网关的设计

提出基于"现场总线 以太网 MODBUS/TCP"方案的网络结构、协议转换的设计思路及网络模型,应用OPC技术解决I/O硬件设备以及软件之间的互操作性问题.在此基础上介绍嵌入式网卡硬件平台的设计及软件开发方法.     

固体硫在超临界/近临界酸性流体中的溶解度(Ⅰ)实验研究

建立了1套静态法测定难挥发物质(固体或液体)在超临界/近临界流体中溶解度的实验装置,并测定了固体硫在近临界硫化氢、超临界CO_2、CH_4及富硫化氢酸性气体混合物中的溶解度数据,取得了较好的结果.     

粘土橡胶纳米复合材料研究进展

简要概述了粘土的有机改性机理、橡胶/粘土纳米复合材料的制备方法、结构与表征和橡胶/粘土纳米复合材料的研究进展.     

PMMA‐modified divinylester/styrene resins: Phase diagrams and morphologies

Binary and ternary experimental cloud‐point curves (CPCs) for systems formulated with a low molar mass synthesized divinylester (DVE) resin, styrene (St), and poly(methyl methacrylate) (PMMA) were determined. The CPCs results were analyzed with the Flory–Huggins (F‐H) thermodynamic model taking into account the polydispersity of the DVE and PMMA components, to calculate the different binary interaction parameters and their temperature dependences. The St‐DVE system is miscible in all the composition range and down to the crystallization temperature of the St; therefore, the interaction parameter expression reported for a higher molar mass DVE was adapted. The interaction parameters obtained were used to calculate the phase diagrams of the St‐PMMA and the DVE‐PMMA binary systems and that of the St‐DVE‐PMMA ternary system at three different temperatures. Quasiternary phase diagrams show liquid–liquid partial miscibility of the St‐PMMA and DVE‐PMMA pairs. At room temperature, the St‐DVE‐PMMA system is miscible at all compositions. Final morphologies of PMMA‐modified cured St‐DVE materials were generated by polymerization‐induced phase separation (PIPS) mechanism from initial homogeneous mixtures. SEM and TEM micrographs were obtained to analyze the generated final morphologies, which showed a direct correlation with the initial miscibility of the system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4539–4549, 2006     

催化剂组成对酸-碱交替沉淀法制备铜基甲醇合成催化剂的影响

采用酸-碱交替沉淀法制备了一种新型的低压甲醇合成催化剂。研究了催化剂组成的影响。当Al和Zr含量固定,随着Cu/Zn摩尔比的增加,催化剂活性先升高后下降,当Cu/Zn摩尔比为1时,活性最高。XRD结果表明,Cu/Zn摩尔比为1时制备的催化剂CuO与ZnO组分间相互均匀分散程度最大。Zr较明显地提高催化剂的活性和耐热性,Mn对催化剂的耐热性提高有一定的作用,La和Ce对提高催化剂活性的作用不大。