醇酸涂料结皮影响因素浅析

分析了醇酸树脂合成原料及合成工艺、复合催干剂和防结皮剂对醇酸涂料结皮性的影响,为解决气干型醇酸涂料的结皮问题提供了一定的建议。     

钴催干剂代替品的研究进展(续)

<正>2.3.2"最好的代钴催干剂"——乙酰丙酮锰螯合物2.3.2.1与钴催干剂相似的催干活性和氧化机理用2,4-戊二酮(又名乙酰丙酮,分子式(CH3COCH2COCH3)和Mn制成螯合物[Mn(acac)3],acac在式中代表乙酰丙酮。这种螯合物对醇酸涂料     

稀土催干剂对改性醇酸树脂催干机理的红外光谱研究 Ⅰ、稀土环烷酸盐类之催干作用

国外对传统催干剂的组成和结构及其在油性涂料(简称“涂料”)中之催干机理,曾作过某些研究。就催干剂而言,其主要研究对象是钴干料,所采用的手段大都是红外光谱法,尤其是近年发展起来的新谓延时性红外光谱技术,更为这方面的研究工作提供了条件。国内在涂料催干机理方     

上海翔资化工有限公司

<正>推荐产品:聚糖树脂CF-2008A:用于自干型醇酸磁漆、酚醛调合漆、环氧酯色漆、底漆和木器漆,在保持原漆质量的同时降低原料成本5%~10%,VOC含量减少15%~20%。CF-3008A:用于自干溶剂型丙烯酸涂料,具有增稠、防沉、促干的效果。高效复合催干剂是一种高效、价廉且使用方便的涂料催干     

醇酸树脂涂料干燥机理的研究进展

综述了醇酸树脂的干燥机理及其研究进展，包括采用各种仪器对醇酸树脂干燥过程进行分析和测试，讨论了各种催干剂的催干机理，指出了醇酸树脂催干剂的发展趋势。     

钴催干剂代替品的研究进展

阐述了取代钴催干剂的必要性。介绍了2-乙基己酸锰和2,2'-联吡啶螯合物代钴催干剂、乙酰丙酮锰和双核锰等新型代钴催干剂,以及还原剂/铁复合的非锰基催干剂等与钴相比较的催干活性与涂膜性能;对基于硫醇-烯化学和钒催干剂结合作为高固体分醇酸涂料在低温、高湿条件下快干的催干剂体系也作了介绍。     

催干剂对水性醇酸树脂涂料性能的影响

以水性丙烯酸改性的醇酸树脂为基料配制水性木器涂料,探讨了涂料配方中催干剂的用量及催干剂的种类对水性醇酸涂料储存稳定性、干燥性能和涂膜耐水性等性能的影响。从醇酸树脂氧化成膜过程,分析催干剂对干燥性能的影响。初步解决了水性醇酸涂料催干剂在使用中应注意的问题。     

钒催干剂在醇酸树脂漆中的应用

钒催干剂用于自干型醇酸树脂漆中具有比钻催干剂更强的氧化催干效果，４％的ＤＧ－Ⅱ催化剂在醇酸漆中的用量在０．２－０．４％，油漆的各项性能均达标准要求。     

国内外化工简讯

由化工部涂料工业研究所研制成功的代钴稀土催干剂新技术,于1990年8月29日在河南省新郑县通过化工部鉴定。国务院稀土办、国家科委派人参加了会议。目前,该产品已在新郑县化工塑料厂批量生产。催干荆是气干型涂料的重要助剂。近几年,全国涂料年产最约有86万吨,需加催干剂的涂料为58万吨,占总最的67.6％。传统的催干剂是钴/铅催干剂体系,在涂料行业中使用多年,由于铅毒性大,不利于操作     

催干剂在水性醇酸涂料中的应用

介绍了催干剂在水性醇酸涂料中的应用。讨论了催干剂类型和用量对水性醇酸涂料性能的影响。     

Beta-Ta4AlC3 is not formed by transformation from α-Ta4AlC3

In this paper, we solve the long-unsolved problem of whether β-Ta₄AlC₃ can be transformed from α-Ta₄AlC₃. By utilizing Ta, Al, and C as initial materials with molar ratios ranging from 4.0/1.2/2.6–4.0/2.0/2.6, it is shown that the synthesis of β-Ta₄AlC₃ is largely affected by the content of Al, and it is confirmed that α-Ta₄AlC₃ is stable at 1600 °C. Furthermore, by modifying the sintering temperature of the samples (4.0/1.2/2.6, 4.0/1.4/2.6, and 4.0/2.0/2.6) from 1450 °C to 1600 °C, the reaction paths of α-Ta₄AlC₃ and β-Ta₄AlC₃ are systematically investigated. It is determined that the β-Ta₄AlC₃ phase forms through the reaction among Ta₂C, C, and Ta_0.6Al_0.4 and the reaction between Ta₂AlC and TaC. For the α-Ta₄AlC₃ phase, there are also two reaction pathways: one from the reaction among Ta₂C, C, and Ta_0.6Al_0.4, and the other from the combination among Ta₃Al₂C, Ta₂C, C, and TaC.     

Structure,magnetic, electrical transport and magnetoresistance properties of La0.67Sr0.33Mn1−xFexO3 (x=0–0.15) doped manganite coatings

We have undertaken a systematic study of the effect of Fe³⁺ doping on the crystal structure, magnetic, electrical transport and magnetoresistance properties of La_0.67Sr_0.33Mn_1−xFe_xO₃ (0≤x≤0.15) polycrystalline coatings prepared by the sol-gel and screen printing method. The X-ray powder diffraction and Reitveld refinement results indicate that the partial substitution of Mn³⁺ ions by Fe³⁺ ions does not introduce noticeable lattice distortion and structural transition. Magnetic measurements show that Fe³⁺ ions significantly lowers the Curie temperature, and the magnetization at low temperatures first increases and then decreases with further Fe³⁺ doping. The Fe³⁺ doped manganites (x>0.05) are semiconductors with high resistivity, as the consequence of low number of available hopping sites of charge carriers. The most stimulating result obtained is that the magnetoresistance property is greatly enhanced around the percolation threshold (x=0.05) of Fe³⁺ ions in this system and the percolative phase separation is responsible for the anomalous behavior.     

The study of granular agglomeration mechanism

The purpose of this study was to determine the effects of the properties of different binders on the granular agglomeration mechanism for the fabrication of pharmaceuticals. The raw materials included calcium carbonate powders with an average particle size of 32-75 μm and four different grades (4000, 6000, 8000 and 10,000) of polyethylene glycol (PEG) used as binders. The raw material was mixed with the binder in a high shear mixer. The surface structure of the granules was analyzed by low vacuum scanning electron microscope (LV-SEM) examination. Three major agglomeration mechanisms are discussed in this study: nucleation, consolidation and coalescence. The results showed that the agglomeration growth rate increased with increasing binder viscosity during the nucleation stage, but the exact opposite phenomenon occurred in the consolidation stage. Observation of the granular surfaces showed the surfaces to be full of fine powder in the nucleation stage, but PEG crystals appeared on the surface in the consolidation stage. During the coalescence stage, the granules grew quickly due to collisions and the surface structures of the granules became full of binders, as can be seen from the LV-SEM photographs.     

The oxidation resistance mechanism of SiC-B4C-xAl2O3 ceramics at 1400 ℃ in air atmosphere

The oxidation property of SiC-B₄C-xAl₂O₃ (x ranges from 0 wt% to 30 wt%) ceramics was studied in air at 1400 ℃. Results show that the porous oxide layer becomes dense and smooth with addition of Al₂O₃. When the content of Al₂O₃ is proper, the DOP (degree of polymerization) of borosilicate network can be improved with increase of Al₂O₃ content, inhibiting the migration of atoms and molecular groups. With that, the crystallization of SiO₂ and volatilization of B₂O₃ can be restrained. When the content of Al₂O₃ is excessive, the DOP of borosilicate network will be decreased, deteriorating the oxide layer morphology. It is believed that the damage of borosilicate network by excess Al₂O₃ should be responsible for this phenomenon. In this research, the SiC-B₄C ceramic with optimal oxidation resistant can be obtained when the content of Al₂O₃ is 15 wt%.     

Synthesis of α-Si3N4 whiskers or equiaxed particles from amorphous Si3N4 powders

Silicon nitride (Si₃N₄) particles with different morphologies have been used in many fields. In this work, α-Si₃N₄ whiskers and granular particles with high-phase purity were successfully tailored by the controllable crystallisation process of amorphous Si₃N₄ powders under different N₂ pressure. Impressively, α-Si₃N₄ whiskers were prepared by simply heat treating amorphous Si₃N₄ powders at 1550 °C for 2 h under the low N₂ pressure of 0.2 MPa, whereas equiaxed α-Si₃N₄ particles with uniform size of ~280 nm were obtained under an elevated N₂ pressure of 2.0 MPa. With the evaluated N₂ pressures and temperatures, large scale α-Si₃N₄ whiskers or equiaxed α-Si₃N₄ particles could be produced. The growth mechanisms of the α-Si₃N₄ particles with distinct morphologies were rationally proposed, and these consist of two main growth processes. First, amorphous Si₃N₄ powders decomposed into Si(g) and N₂(g) under high-temperature treatment. Subsequently, N₂(g) dominated the recombination of the evaporated chemical with the Si₃N₄ molecule. The initial N₂ concentration, which plays a key role in tailoring the shape and size of products, was controlled by the N₂ pressure.     

无卤阻燃剂二乙基次磷酸铝的热降解和阻燃机理

通过不同分析方法研究了二乙基次磷酸铝（AlPi）受热后的变化过程。结果证实,随温度升高AlPi会通过自身挥发将阻燃性含磷物质释放到气相中;此外还存在一种热降解机理,分解后含磷物质留在固相中,降低了气相阻燃能力;进一步分析发现,在与火焰温度接近条件下,挥发到气相中的二乙基次磷酸铝会充分裂解成磷原子,进而形成含磷自由基淬灭剂起气相阻燃作用。     

Microstructure and ablation mechanism of C/C-ZrC-SiC composites in a plasma flame

Ablation behavior of C/C-ZrC-SiC composites was investigated using a plasma flame. The composites exhibited excellent ablation performance. After ablation for 180 s, three kinds of ablation behavior appeared from the border to the center on the surface, which were closely related to the temperature and denudation force. Additionally, the ablation behavior in the cross-sectional direction of the composites was mainly controlled by the temperature. During the ablation, ZrC and SiC were oxidized into ZrO₂ and SiO₂, respectively, resulting in the formation of a ZrO₂-SiO₂ binary eutectic system. The ablation mechanism was also discussed, which could provide strong illustration of the evolution processes of the eutectic system at different temperatures.     

Heterovalent ions incorporated pyrochlore Sm2Zr2O7 ceramic for enhanced NO2 sensing

The present work demonstrated the heterovalent ions incorporated pyrochlore Sm₂Zr₂O₇ ceramic with high NO₂ sensitivity through molecular insights into the bond of [BO₆] unit and the sensing mechanism. An effective B-site strategy was developed to prepare a series of defective Sm2Zr1.95X0.05O7+δ (SZX, X= Mn²⁺, Ga³⁺, Sn⁴⁺, Nb⁵⁺, W⁶⁺) ceramics to create oxygen vacancies or interstitial oxygen induced which enhances the NO₂ sensing performances. The structural analyses carried out by XRD, SEM, XPS, Raman and the NO₂ adsorption on a cold surface of the sensor clarified the potential sensing mechanism. The electrochemical results clearly indicate that NO₂ sensing properties are closely related to the valence of doped cations. The sensor of Sm2Zr2O7 with Nb⁵⁺ arranged at B sites indicates high sensitivity, quick response/recovery speed, excellent selectivity and stability compared with others, exhibiting great application prospects for the automotive equipment.