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排序方式: 共有72条查询结果,搜索用时 31 毫秒
1.
Latexes with intrinsic crosslink activity 总被引:1,自引:0,他引:1
In order to develop and study ‘two pack in one pot’ systems, i.e. binder systems consisting of a blend of complementary reactive latexes, epoxy- and amino-functional latexes were prepared and characterised, with atte lion especially directed to control of the number of functional groups and control of the molecular weight. The investigation is focused on the control of the molecular weight of epoxy-functional latexes and on the incorporation of amino groups in latexes by using amino-functional methacrylic monomers. To determine the reactivity of the epoxy and amino groups and to check which factors influence the crosslink reaction a number of blends were prepared from both solution and emulsion copolymers and dried at ambient temperatures. It was found that the major factors, which affect the efficiency of crosslinking, are the Tg and the molecular weight of the copolymers and, in the case of a ‘two pack in one pot system’, the rate of the polymer-polymer reaction in relation to that of the polymer-polymer interdiffusion. 相似文献
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Environmental etch damage to automotive coatings, and scratch and mar of these coatings are an important element of customer satisfaction as well as a significant warranty repair consideration for automotive companies. The conditions that result in environmental etch are examined and a laboratory test proposed. Data from this test are compared to automotive hoods exposed in Florida. The performance of various crosslinking chemistries is discussed and the requirements for improved environmental etch are outlined. Scratch and mar performance of these systems is also reviewed. We have found that coatings respond to physical stress by elastic recovery, by plastic flow and by brittle fracture. Classifying types of damage in this way is important for understanding the chemistry needed for improved scratch and mar of coatings. 相似文献
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An aromatic rich, amine cured epoxy network (initial glass transition temperature 250 °C), was irradiated in air (pressure 0.22 MPa), at 30 and 120 °C, by gamma rays with two dose rates 2 and 20 kGy/h, for doses upto 70 MGy. The following characteristics were recorded, thickness of oxidised layer (TOL) from IR microspectrophotometry, flexural strength σR, toughness KIC and glass transition temperature Tg. σR decreases from 120 MPa to about 40 MPa in the most degraded samples. This decrease is sharply linked to TOL showing the key role of the oxidised layer in crack initiation. KIC decreases from 0.7 to 0.55 MPa m1/2. Data are too much scattered to allow a kinetic study but it appears that, in the early period of exposure, KIC decreases more rapidly at 120 °C than at 30 °C. Tg decreases from 250 to 140 °C in the most degraded samples, and the decrease is faster at 30 °C than at 120 °C. The decrease of Tg is attributed to a predominant chain scission process. The decrease of KIC can be attributed to a combination of chain scission and physical ageing or chain scission and crosslinking. A relationship between Tg and the number of chain scissions, derived from the Di Marzio's theory, is proposed. 相似文献
6.
Youngsang Kim 《Microelectronic Engineering》2008,85(3):582-586
We have characterized the electron beam lithography (EBL) properties of the new negative tone resists, ma-N2410 and ma-N2405. These negative resists reacts under low electron dose values from 10 to 140 μC/cm2, tested using 10, 20, 28 keV electron beam. There was negligible loss of pattern height, which was attributed to the combined dose of the incident electron beam and the backscattered electrons. Experimental tests were performed under various EBL writing conditions of dose value, developing time, line-width and resist thickness. Our investigation showed that these new commercially available resists have high resolution and high contrast with non-chemical amplification, useful for micro-fabrication application. 相似文献
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The characteristics of networks formed in cured ‘reworkable’ epoxy thermosets capable of controlled thermal degradation were studied. Dynamic mechanical thermal analysis, swelling measurements, and glass transition temperature measurements were used to obtain information regarding the time and temperature dependence of the crosslink densities of these materials. By applying isothermal conditions, networks containing up to 36 mol% non-degradable components could be completely degraded, i.e. progress from a network of infinite molecular weight to a finite one with zero crosslink density. Percolation theory was used to facilitate the interpretation of these results. The degradation behavior of the reworkable thermosets were well-described by gel degradation theory, i.e. the reverse of the gelation process, and the experimental results were in good agreement with calculated values obtained by replacing the extent of reaction, p, in Macosko and Miller's branching theory with the extent of degradation, 1−p. 相似文献
8.
Two castor oil-based monomers, (1) norbornenyl-functionalized castor oil (NCO), which has ∼0.8 norbornene rings per fatty acid chain and (2) norbornenyl-functionalized castor oil alcohol (NCA), which has ∼1.8 norbornene rings per fatty acid chain, have been prepared. Ring-opening metathesis polymerization (ROMP) of different ratios of NCO/NCA using the 2nd generation Grubbs catalyst results in rubbery to rigid biorenewable-based plastics with crosslink densities ranging from 318 to 6028 mol/m3. Increased crosslink densities result in shorter gelation times, better incorporation of the monomers into the polymer network, and much less soluble materials in the bulk materials. The increased crosslink densities obtained by adding NCA enhance the thermal properties, including the glass transition temperature (Tg) and room temperature storage modulus, which increase from −17.1 °C to 65.4 °C and from 2.4 MPa to 831.9 MPa, respectively. The TGA results, where T10 increased from 285 °C to 385 °C, illustrate that improved thermal stabilities can be obtained for thermosets with higher crosslink densities. Young’s modulus (11-407 MPa), tensile strength (1.6-18 MPa) and toughness (0.14-1.6 MPa) are also improved dramatically with higher crosslink densities. 相似文献
9.
Crosslinkable ruthenium complex dye, Ru(2,2′-bipyridine-4,4′-bicarboxylic acid)(4,4′-bis((4-vinyl benzyloxy)methyl)-2,2′-bipyridine)(NCS)2 (denoted as Ru-S dye), was synthesized and characterized using 1H-NMR, 13C-NMR, Fourier transform infrared (FTIR) and UV/vis spectroscopies.The power conversion efficiency of dye-sentitized solar cell (DSSC) using Ru-S and liquid electrolyte containing lithium iodide (LiI) reached 7.53% under standard global AM 1.5 full sunlight, which is partly attributed to Li+ being coordinated by Ru-S as verified by ATR-FTIR spectroscopy. As Ru-S was further crosslinked with glycerol propoxylate triacrylate (GPTA), not only 89% of dye retained on TiO2 mesoporous surface after rinsed by 0.1 N NaOH aqueous solution, the power efficiency was also increased to 7.88%. As poly(methyl acrylate) was used to gel the electrolyte system, the power efficiency of DSSC with Ru-S dye was 6.96% but increased to 7.57% after crosslinking with GPTA. Notably, both DSSCs showed a good long-term stability after one month storage. 相似文献
10.
Mery L. G. Vieira Cláudio P. Pinheiro Keli A. Silva Sabrina F. Lutke Tito Roberto Sant' Anna Cadaval Guilherme Dotto 《Chemical Engineering Communications》2019,206(11):1474-1486
AbstractThe aim of this work was to coat glass beads with chitosan and cyanoguanidine-crosslinked chitosan and, afterward, to verify the potential of the coated beads as adsorbent for the FD&C Red 40 dye in fixed bed column. The coating was realized in eight experimental conditions, varying the technique (dip coating or casting) and the coating solution composition (different proportions of chitosan, cyanoguanidine, glycerol, sorbitol, sodium alginate, NaOH and CaCl2). The beads coated in the eight experimental conditions were then applied to adsorb FD&C Red 40 in a fixed bed column, from aqueous solutions at pH 3.0 and 6.0. The breakthrough curves were fitted according to Thomas and Yoon-Nelson dynamic models. The coating was dependent of the solution composition. The casting technique presented coating percentage values of 92%, while the dip coating technique presented only 43%. The breakthrough curves revealed that the use of glass beads coated with cyanoguanidine-crosslinked chitosan had good performance, attaining adsorption capacity values higher than 80?mg g?1. Thomas and Yoon-Nelson models were able to predict the breakthrough curves in all conditions. 相似文献