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1.
A Kinetic Evidence for the Nitroxyl Radicals Recycling Mechanism in the Photostabilizing Process of HALS 总被引:1,自引:0,他引:1
XiaoXuanLIU XingHongZHANG GuangGuoWU JianWenYANG ZhaoHuaZENG YongLieCHEN 《中国化学快报》2003,14(10):1085-1088
The photoinduced bulk polymerization of a reactive-hindered amine fight stabilizers(r-HALS), 4-acryloyl-2, 2, 6, 6-tetramethylpiperidinyl (ATMP), was performed at 80℃ by using a DPC technique. An unique periodic exponential attenuation-type oscillating curve was found when the polymerization was carried out in air, but this phenomenon was not found in nitrogen.It is supposed that this unique kinetic performance may be attributed to nitroxyl radicals that are produced in situ from the oxidation of ATMP. ATMP polymer with narrow polydispersity (d =1.03) can be obtained by photoinduced solution polymerization of ATMP. The signal detected in ESR may be assigned to the nitroxyl radicals in the matrix of ATMP polymer. Since this kind of recycling of nitroxyl radicals is well documented for the photostabilizing mechanism of HALS, the present results may serve as a kinetic evidence for this mechanism. 相似文献
2.
To improve the water tree resistance of PE, linear low-density polyethylene (LLDPE) was compounded with sodium acrylate (NaAA) for in situ polymerization, in which NaAA was fbrmed through the neutralization of acrylic acid (AA) with sodium hydroxide (NaOH) before adding dicumyl peroxide (DCP) to initiate the in situ graft polymerization and homo polymerization. A series of LLDPE/NaAA compounds were investigated for their water absorption ratio (WAR) measurement, water treeing, mechanical and dielectric properties. The results strongly suggest that NaAA can improve the water tree resistance of LLDPE. In addition, the LLDPE/NaAA compounds possess satisfactory mechanical properties and dielectric properties. Characterization of LLDPE/NaAA compounds by using Fourier transform infrared spectrometry (FTIR) suggests that the neutralization and polymerization reaction could be achieved effectively. Using adequate DCP content is the key factor for controlling the polymerization of NaAA with precise conversion ratio. 相似文献
3.
Xiao-chun Wang Gui-sheng Yang Qiang Zheng 《高分子科学》2007,(5):473-481
20 wt% polyamide 12(PA1212)pellets were dissolved in molten caprolactam.The caprolactam was then catalyzed at 180℃and polymerized by means of anionic ring-opening polymerization to produce in situ blends of the resultant polyamide 6(PA6)and PA1212.Mechanical blends with same ingredient were prepared through melt blending on a twin-screw extruder.Scanning electron microscopy(SEM)observation revealed that contrary to the mechanical blends with small spherulites embedded in the matrix,no phase-separation existed in the in situ blends.The results of thermal analysis by differential scanning calorimetry(DSC)showed that single melting peak and crystallization peak existed for the in situ blends,while two melting and crystallization peaks appeared for the mechanical blends.The in situ blend film and the mixed blend film,both cast from a dilute formic acid solution with a concentration of 0.5 g/L,remained similar crystallization and melting behavior as above.It is proved by solution ~(13)C-NMR analysis that transamidation took place during the in situ blending,and it is suggested that the combination of temperature increasing and the basic surrounding derived from NaOH during polymerization resulted in the occurrence of transamidation.Furthermore,it is proposed that the interchange reaction between PA1212 and PA6 also resulted from the degradative reaction during the anionic polymerization. 相似文献
4.
p-Nitrophenol imprinted nanoparticles with a size range of 150-300 nm in diameter were prepared through miniemulsion polymerization. The imprinted polymer exhibited higher adsorption capacity for p-nitrophenol than the nonimprinted polymer. The hydrolysis of paraoxon in aqueous phase can be accelerated in the presence of the p-nitrophenol imprinted nanoparticles. The hydrolysis rate of paraoxon incorporated with the imprinted nanoparticles was 2.83×10-7 mol/(L·min), which was about 3.7 times higher compared to the non-imprinted nanoparticles, 12.7 times higher to the spontaneous hydrolysis. The nanoparticles have been mixed with polyacrylonitrile solution and electrospun into nanofibers, which can also be used to accelerate the hydrolysis of paraoxon and conveniently separated from liquid phase for further processing. 相似文献
5.
The smoldering weakness of alginate fibers can be effectively suppressed by simple blending with flame retardant viscose fibers. The char formed by flame retardant viscose fibers can prevent the heat transmission and suppress the smoldering of alginate. 相似文献
6.
Triphase polyimide nanocomposite films were fabricated using barium titanate (BaTiO3) with high dielectric constant and silver (Ag) with high conductivity as fillers. In situ method was utilized to obtain the homogeneous dispersion of nanoparticles. The in situ polymerization of polyimide precursor-poly(amic acid) was performed in the presence of BaTiO3 particles. Silver compound 1,1,1-trifluoro-2,4-pentadionato silver(I) was added into the BaTiO3 containing poly(amic acid) solution to achieve silver nanoparticles via in situ self metallization technique. The thermally induced reduction converted silver (I) to metallic silver with concomitant imidization of poly(amic acid) to polyimide. Both BaTiO3 and silver nanoparticles were uniformly dispersed in the polyimide substrate. The dependence of dielectric behavior on the BaTiO3 and Ag contents was studied. The incorporation of small amount of silver nanoparticles greatly increased dielectric constant of composite films. 相似文献
7.
The effect of silica nanoparticles on the morphology of (10/90 wt%) PDMS/PBD blends during the shear induced coalescence of droplets of the minor phase at low shear rate was investigated systematically in situ by using an optical shear technique. Two blending procedures were used: silica nanoparticles were introduced to the blends by pre-blending silica particles first in PDMS dispersed phase (procedure 1) or in PBD matrix phase (procedure 2). Bimodal or unimodal droplet size distributions were observed for the filled blends during coalescence, which depend not so much on the surface characteristics of silica but mainly on blending procedure. For pure (10/90 wt%) PDMS/PBD blend, the droplet size distribution exhibits bimodality during the early coalescence. When silica nanoparticles (hydrophobic and hydrophilic) were added to the blends with procedure l, bimodal droplet size distributions disappear and unimodal droplet size distributions can be maintained during coalescence; the shape of the different peaks is invariably Gaussian. Simultaneously, coalescence of the PDMS droplets was suppressed efficiently by the silica nanoparticles. It was proposed that with this blending procedure the nanoparticles should be mainly kinetically trapped at the interface or in the PDMS dispersed phase, which provides an efficient steric barrier against coalescence of the PDMS dispersed phase. However, bimodal droplet size distributions in the early stage of coalescence still occur when incorporating silica nanoparticles into the blends with procedure 2, and then coalescence of the PDMS droplets cannot be suppressed efficiently by the silica nanoparticles. It was proposed that with this blending protocol the nanoparticles should be mainly located in the PBD matrix phase, which leads to an inefficient steric barrier against coalescence of the PDMS dispersed phase; thus the morphology evolution in these filled blends is similar to that in pure blend and bimodal droplet size distributions can be observed during the early coalescence. These results imply that exploiting non-equilibrium processes by varying preparation protocol may provide an elegant route to regulate the temporal morphology of the filled blends during coalescence. 相似文献
8.
Surface of TiO2 nanoparticles was modified with the in situ chemical oxidative polymerization of aniline. Polyaniline modified TiO2 nanoparticles (PANI-TiO2 ) were characterized with the FT-IR, XRD, SEM and TEM techniques. Results confirmed that PANI was grafted successfully on the surface of TiO2 nanoparticles, therefore agglomeration of nanoparticles decreased dramatically. Polyvinyl chloride nanocomposites filled with 1 wt% 5 wt% of PANI-TiO2 and TiO2 nanoparticles were prepared via the solution blending method. PVC nanocomposites were analyzed with FT-IR, XRD, SEM, TG/DTA, DSC and tensile test techniques. Effect of PANI as surface modifier of nanoparticles was discussed according to the final properties of PVC nanocomposites. Results demonstrated that deposition of PANI on the surface of TiO2 nanoparticles improved the interfacial adhesion between the constituents of nanocomposites, which resulted in better dispersion of nanoparticles in the PVC matrix. Also PVC/PANI-TiO2 nanocomposites showed higher thermal resistance, tensile strength and Young’s modulus compared to those of unfilled PVC and PVC/TiO2 nanocomposites. 相似文献
9.
A novel amphiphilic copolymer,dipropenoxystyrene anthracene and acrylic acid copolymer(BASA-AA) was designed and synthesized based on divinyl anthracene. The polymer self-assembled rapidly in water to create polymer nanoparticles(BASA-AA NPs)with a uniform size of 45 nm,no dye leakage,and great brightness(Φ= 36%). Because of the enormous number of carboxyl groups on the surface of the particles,it can disperse extremely well in water,and can be used for the rapid detection of copper ion and cysteine(Cys)in pure water, with the limit of detection of 45 nmol/L. The fluorescent intensity of the nanoparticles will be greatly reduced after the introduction of copper ion,realizing the detection of copper ion with high selectivity and sensitivity. A composite probe made of BASA-AA NPs and copper ion can detect Cys in the range of 0.1-10 µμmol/L,with the detection limit of 84 nmol/L,due to the high binding capacity of the sulfhydryl group and copper ion. The method is simple and rapid in material synthesis and preparation,and shows high selectivity and sensitivity in pure water. © 2023, Youke Publishing Co.,Ltd. All rights reserved. 相似文献
10.
柴佩君薛俊萍朱瑞瑞王玉朦杨刚强毕毅宋志花 《分析试验室》2023,(1):125-132
Ginsenosides possess pharmacological activities such as anti-aging,cardiovascular protection,and improving immunity. However,the detection and analysis of ginsenosides commonly suffer from the problem of low sensitivity owing to the complex matrix and low content of ginsenosides. Chromatographic technology was often used to detect ginsenosides owing to the advantages of high accuracy,high sensitivity,good reproducibility and low sample consumption,etc. In this review,the application of chromatographic analysis technologies in ginsenosides detection was summarized. First of all,accuracy of test results for the ginsenosides can be effectively improved by using high performance liquid chromatography(HPLC)combined with various detectors. Secondly,the combination of HPLC with mass spectrometry can be utilized for qualitative and quantitative analysis of ginsenosides, as well as other fields, such as metabonomics, pharmacokinetics, intestinal microorganisms and quality control. Moreover,the application of gas chromatography in analysis of ginsenosides was reviewed. Briefly,with the continuous development of chromatographic technology,the degree of accuracy for ginsenosides detection was effectively improved,which is beneficial to realize the effective analysis of ginsenosides. © 2023, Youke Publishing Co., Ltd. All rights reserved. 相似文献
11.
An improved method for preparing melamine cyanurate (MCA)based flame retardant polyamide 6 (FRPA6)materials has been proposed.This processing method,i.e.,improved in situ polymerization,was used to synthesize flame retardant PA6.In situ formed MCA nanoparticles were supposed to be linked to PA6 chains in the ε-caprolactam hydrolytic polymerization system to obtain startype polymers for the first time.Through TEM photographs,it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm,are nanoscaled,highly uniformly dispersed in the PA6 matrix.Synthesized flame retardant PA6 have good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix. 相似文献
12.
Preparation of flame retardant polyamide 6 composite with melamine cyanurate nanoparticles in situ formed in extrusion process 总被引:1,自引:0,他引:1
This paper is focused on in situ preparation of melamine cyanurate (MCA) nanoparticles from reaction of melamine (MEL) and cyanuric acid (CA) and their flame retardant polyamide 6 (PA6) composite in the extrusion process through a novel reactive processing method. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were utilized to characterize the in situ formed MCA nanoparticles and their blends with PA6. Introduction of pentaerythritol (LTP) and water-bound plasticizer dioctyl phthalate (DPT) into the extrusion reaction system greatly inhibits the evaporation of water required for melamine and cyanuric acid reaction at high temperature (higher than 180 °C), laying a foundation for successful in situ preparation of MCA through reactive processing. XRD and FT-IR measurements indicate that under the effect of pentaerythritol, dioctyl phthalate and water, melamine really reacts with cyanuric acid to in situ form MCA in extrusion process. The reaction degree is close to 100%. A very important finding through SEM is that the in situ formed MCA particles, which were found to have aspect ratio of about 7.5, radial size in the range of 70-300 nm (mostly 70-90 nm) and crystallite size of less than 22 nm, are uniformly dispersed in the matrix PA6 at nanoscale. The in situ formed MCA nanoparticles greatly improve the flame retardancy and the mechanical properties of flame-retarded PA6 materials, and the introduced plasticizer dioctyl phthalate also ameliorates the related impact property. The obtained flame-retarded PA6 materials have good comprehensive performance with flame retardancy UL-94 V-0 rating at 1.6 and 3.2 mm thickness, tensile strength 48.0 MPa, elongation at break 106.3% and Izod notched impact strength 8.92 kJ/m2. Compared with flame-retarded PA6 material with in situ formed MCA, the one prepared through conventional blending of PA6 with commercial MCA product has improved tensile strength but deteriorated impact strength and flame retardancy. 相似文献
13.
A novel strategy to synthesize hybrid metal–polymer nanocomposites has been achieved based on in situ free radical suspension and bulk polymerization techniques. An organometallic precursor complex is dissolved in a liquid monomer phase prior to polymerization, where upon the precursor molecules are immobilized inside the polymer matrix during its formation. In a separate step, metal nanoparticles are then formed by H2-assisted reduction of the precursor in the polymer product in supercritical carbon dioxide (scCO2). The synthesized nanocomposites were characterized by GPC, TGA, SEM and TEM. It is shown that the metal nanoparticles are uniformly distributed inside the polymer matrix and the inclusion of the metal precursor has no significant influence on the polymerization process. The current work represents a simple and universal way to prepare a variety of metal–polymer nanocomposite functional materials. 相似文献
14.
以聚乙烯醇(PVA)为原料, 植酸(PA)和氨基-聚倍半硅氧烷(NH2-POSS, NP)为交联剂, 通过冻融循环法制得PVA/PA/NP复合水凝胶, 再以其为模板, 通过吡咯的原位聚合制得PVA/PA/NP-PPy复合导电水凝胶, 克服了聚吡咯材料易脆、 疏水的特性, 进一步改善了水凝胶的导电性和灵敏性. 循环拉伸实验结果表明该水凝胶具有良好的自回复能力, 电导率高达7.53 S/m, 从I-V曲线可知其作为柔性可穿戴应变传感器的最高检测电流可达 9.029 mA, 灵敏度因子可达6.796, I-T曲线表明该传感器可以准确地通过电流信号变化来监测人体的各种微小运动. 相似文献
15.
Melamine cyanurate-microencapsulated red phosphorus flame retardant unreinforced and glass fiber reinforced polyamide 66 总被引:1,自引:0,他引:1
A novel microencapsulated red phosphorus (RP) was prepared through the molecular self-assembly of melamine cyanurate (MCA). Compared with the conventional encapsulated RP, MCA-encapsulated RP (MERP) shows simpler and more environment-friendly preparation process higher thermal stability and lower moisture absorption. With MERP filled in unreinforced polyamide 66 (PA66) and glass fiber (GF) reinforced PA66, flame retardant materials with satisfactory flame retardancy and mechanical performance can be obtained. The influence of the MCA/RP ratio on the flame retardancy as well as the condensed phase of MERP flame retardant PA66 was investigated to reveal the nitrogen-phosphorus (N-P) synergistic flame retarding effects between MCA and RP. 相似文献
16.
研究了十二烷基硫酸钠对原位晶化制备小晶粒NaY的影响,并以包含小晶粒NaY的原位晶化产物为母体,通过铵交换和稀土离子交换制备出了REUSY催化剂.采用X射线衍射(XRD)、扫描电镜(SEM)、X射线荧光(XRF)及N2物理吸附-脱附等手段对样品进行了表征,采用微反活性评价装置和小型固定流化床(ACE)评价了所制备催化剂在重油催化裂化反应中的催化性能.结果表明:在原位晶化合成NaY的体系中,添加高岭土微球质量5%的十二烷基硫酸钠,可以将分子筛的平均晶粒尺寸由540 nm减小到250 nm.相比于常规的原位晶化型流化催化裂化(FCC)催化剂,以包含小晶粒NaY的原位晶化产物为母体所制备出的催化剂,在反应原料的转化率、裂化产物的选择性以及抗积碳性能等方面均有明显的提高或改善. 相似文献
17.
长余辉纳米材料具有独特的发光性质, 能在激发光关闭后持续发光. 通过收集激发光关闭后的长余辉发光信号可以有效消除背景信号的干扰. 此外, 长余辉材料在成像时无需原位激发, 可以减少生物体系的组织自发荧光和光散射干扰, 提高生物成像和检测的灵敏度. 由于这种独特的光学特性, 长余辉纳米材料在生物传感/生物成像以及疾病治疗等领域被广泛应用. 近年来, 为满足疾病相关生物标志物的体外检测及体内生物成像的应用要求, 控制合成发光性能优异、 生物相容性好的长余辉纳米材料成为研究热点. 相似文献
18.
通过两步聚合法合成具有温度敏感性能的核-壳型聚(苯乙烯-N-异丙基丙烯酰胺)/N-异丙基丙烯酰胺共聚3-(甲基丙烯酰氧)丙基三甲氧基硅烷(P(St-NIPAM)/P(NIPAM-co-MPTMS))复合微凝胶材料.以经3-巯丙基-三甲氧基硅烷(MPS)表面修饰的复合微凝胶为载体,乙醇为还原剂,在温和条件下控制性还原制备纳米银微粒.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外(FT-IR)光谱仪、X-射线光电子能谱(XPS)、X射线衍射(XRD)仪、热分析(TGA)和紫外-可见(UV-Vis)分光光度计等手段对P(St-NIPAM)/P(NIPAM-co-MPTMS)-(SH)Ag复合微凝胶的结构、组成和性质进行表征.同时,以硼氢化钠还原对硝基苯酚为模型反应,对该复合材料催化还原性能进行了评价.结果表明,载体含有巯基的有机-无机杂化网络结构的限域作用使原位合成的纳米银微粒的分散性较好.载体微凝胶壳层链节中无机组分MPTMS的引入在一定程度上降低了复合凝胶温敏性,但复合凝胶仍表现出催化还原反应的温敏性调控和良好的催化活性.以上实验结果与温敏性PNIPAM链节被无机网络分隔而有利于反应传质及壳层巯基对原位纳米银形成尺寸和空间分布的有效控制有关.本研究对功能性金属纳米催化复合材料的研究具有积极借鉴意义. 相似文献
19.
A CuY zeolite prepared by liquid phase ion exchange was characterized by X-ray photoelectron spectroscopy, pyridine in situ Fourier transform infrared (in situ FTIR) spectroscopy, and ammonia temperature programmed desorption. The effect of cyclohexene on the adsorption of thiophene over the prepared CuY zeolite was explored by in situ FTIR. In particular, the role of the zeolite's Br?nsted acidity was investigated in the adsorption process. The results show that the percentage of Cu+ on the surface of the CuY zeolite can reach 77%. The surface acidity of the CuY zeolite mainly comprises medium and strong Br?nsted acidity and Lewis acidity. According to the adsorption results, cyclohexene negatively influences thiophene adsorption on the Br?nsted or Lewis acid sites in CuY by competitive adsorption. Although polymerization of thiophene and cyclohexene can occur easily on the HY or REY zeolites, the presence of Br?nsted acids in the CuY zeolite was not sufficient to polymerize either thiophene or cyclohexene. This difference may be caused by an anti-synergistic effect between the Cu ions of the CuY zeolite and neighboring Br?nsted acid sites, the result of which inhibits the polymerization of adsorbed thiophene and cyclohexene. 相似文献
20.
样品中各元素原位、微区、高分辨率的空间分布特征具有现实而重要的研究意义. 在生物样品中,元素原位空间分布特征可以作为生理过程的指示指标,揭示代谢途径,并可反映周围环境特征对生物体的影响方式. 在地质样品中,元素原位空间分布特征可以作为矿产评估依据,也可作为研究环境地球化学变化过程的重要指标. 目前常用的几种微区元素原位分布特征测试技术包括:微区XRF技术(μXRF)、同步辐射技术(SR)、能谱电子显微镜联用技术(EM-EDS)、电子探针技术(EP)、激光剥蚀联用电感耦合等离子体质谱技术(LA-ICP-MS)、激光诱导击穿等离子发射光谱技术(LIBS)等. 根据其测试原理,这些技术在是否无损、是否定量检测、适合样品类型和大小、前处理方式复杂程度、检出限高低、分辨率大小等方面存在差异. 介绍和总结了当前主流的微区原位元素分布检测技术,分析比较了各种技术的优缺点及其适用的样品类型和应用范围,对标准样品的选择、数据校准处理及可视化成图等方案进行初步探讨,为相关的科研分析工作提供技术参考. 相似文献