金属对厌氧胶贮存稳定性的影响

在厌氧胶中存在的微量金属对贮存稳定性具有明显影响，可以用添加螯合剂的方法来改善胶液贮存稳定性。     

螺纹锁固厌氧胶在轨道车辆中的应用

按照国标GB／T18747．1—2002的试验要求并结合轨道车辆的行业规范,对中等强度螺纹锁固厌氧胶在各种条件下进行使用并检测。对检测结果进行对比分析,进一步证实在轨道车辆项目中使用螺纹锁固厌氧胶的必要性,规定螺纹锁固厌氧胶必须使用的部位。     

In situ FTIR spectroscopic studies of electrooxidation of ethanol on Pd electrode in alkaline media

Electrooxidation of ethanol on a polycrystalline Pd disk electrode in alkaline media was studied by in situ Fourier transform infrared (FTIR) reflection spectroscopy. The emphasis was put on the quantitative determination of intermediates and products involved in the oxidation. It has revealed that most of ethanol was incompletely oxidized to acetate. The selectivity for ethanol oxidation to CO₂ (existing as CO₃²⁻ in alkaline media) was determined as low as 2.5% in the potential region where Pd electrode exhibited considerable electrocatalytic activity (−0.60 to 0.0 V vs. SCE). Nevertheless, the ability of Pd for breaking C-C bond in ethanol is still slightly better than that of Pt under the same conditions. Besides, a very weak band of adsorbed intermediate, bridge-bonded CO (CO_B) was identified on the Pd electrode for the first time, suggesting that CO₂ and CO₃²⁻ species may also be generated through CO pathway (i.e., indirect pathway).     

In situ studies of heterogeneous catalysis: Diffractometric and spectroscopic approaches

Lessons are drawn from the work of molecular biologists who have succeeded in elucidating the mechanisms of many enzymatic processes from X-ray crystallographic analyses of data recorded on the catalyst-reactant system prior to and after catalytic reaction. The use of in situ infrared spectroscopy to clarify the processes of adsorption and catalytic reactions on uniform heterogeneous catalysts is exemplified through a series of studies of the dehydration of the four isomers of butanol over H-ZSM-5.     

Hybrid emulsifiers enhancing polymerization stabilities and properties of pressure sensitive adhesives

In this study, a series of (anionic and nonionic) emulsifiers were investigated to prepare acrylic pressure sensitive adhesives (PSA) with core‐shell structure by semicontinuous emulsion polymerization. The cloud point of different emulsifiers was characterized to explain the emulsifier effects on the emulsification ability. It was interestingly found that the hybrid emulsifiers (anionic coupling with nonionic) with optimized compositions could enhance the stability of emulsion system and improve the properties of PSA compared with the mono‐emulsifier. The stability of emulsion polymerization, the appearance of the emulsion system and the properties of PSA were studied in details by changing the proportion and the content of hybrid emulsifiers. When the ratio of sodium dodecyl sulfate (SDS: anionic emulsifier) to polyoxyethylene alkyl phenyl ether (OP‐10: nonionic emulsifier) reached 2 : 1, the content of hybrid emulsifiers reached 3 wt % and the reaction temperature was around 80°C, a better emulsion system was obtained in terms of comprehensive properties. At this condition, the synthesized PSA demonstrated the good holding power and 180° peel strength properties with fair tacky property, which was promising for industrial applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of one-component polyurethane powder adhesives by the solution polymerization technology

A new technology integrating the synthesis and granulation was adopted to prepare the one-component polyurethane powder adhesives (PPAs) by the solution polymerization. The influence of R_total, neutralization, and types of dispersion solution on the properties of PPAs was investigated. It was found that the initial melting temperature increased and storage stability decreased with increasing R_total. The neutralization reaction between the carboxylic group and amino group made the reduction of the sizing temperature and the increase of the T-peel adhesion strength. The granulation behaviors of the polyurethane (PU) prepolymer under different dispersion solutions showed that the PU prepolymer can be effectively blocked by the 20–30 wt % NaHSO₃ or n-butyl alcohol. Furthermore, the blocked polymers formed small particles with the ideal sizing temperature and peel strength. The excellent adhesive property and thermal stability of PPAs could meet the requirements of the industrial gluing in the fields of packaging, lining, and footwear. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47898.     

Picosecond excimer fluorescence spectroscopy: applications to local motions of polymers and polymerization monitoring

The local motions of α,ω-bis-(1-pyrene)alkanes and pyrene-labelled poly(methyl methacrylate) polymers in solution were characterized by picosecond excimer fluorescence spectroscopy. The experimental results showed that 1,3-bis-(1-pyrene)propane and 1,10-bis-(1-pyrene)decane have similar local motions that bring two pyrene groups together to form excimers. Further, poly(1-pyrenylmethyl methacrylate) and a copolymer of methyl methacrylate and 1-pyrenylmethyl methacrylate in solution were found to have similar local motions that lead to excimer formation. In addition, the viscosity change during the polymerization of methyl methacrylate was monitored by measuring with picosecond fluorimetry the fluorescence lifetime of a trace amount of 1,3-bis-(1-pyrene)propane dissolved in methyl methacrylate.     

Water‐soluble/dispersible cationic pressure‐sensitive adhesives. II. Adhesives from emulsion polymerization

In our previous work, we reported that cationic water‐soluble pressure‐sensitive adhesives (PSAs) could be synthesized in ethanol or methanol. These cationic water‐soluble adhesives would not cause a stickies problem during paper recycling and can be easily removed from the papermaking system by adsorbing on wood fibers. In this study we report the synthesis and application of water‐based cationic PSAs using miniemulsion polymerization. A redox initiator system of cumene hydroperoxide/tetraethylenepentamine was used to force interfacial polymerization. The end‐use properties of the PSAs were evaluated, and the repulpability of the PSAs in paper recycling was studied. It was found that the cationic PSA from miniemulsion polymerization itself was insoluble and nondispersible in water during the paper recycling process. However, if this water‐insoluble cationic PSA from miniemulsion was formulated with a water‐soluble cationic PSA made from ethanol, the solubility or dispensability of the former PSA in water was improved. The molecular weight and degree of crosslinking of the PSA polymer have significant effects on the properties and dispersability of PSA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 347–353, 2004     

Fluorescence spectroscopy as a non invasive tool to follow in situ the polymerization in miniemulsion

Miniemulsion polymerization is a powerful technique to produce a whole variety of latexes with controlled colloidal and chemical properties, which has gained an increasing importance in the past years. For many applications, the following of the kinetics of polymerization is of crucial importance. In this study, we developed a technique based on the use of fluorescent probes that could be a very promising noninvasive method to follow the reaction in situ. It was possible to follow qualitatively the kinetics of methyl methacrylate (MMA) polymerization by measuring the photophysical properties of fluorescent probes sensitive to the modification of the viscosity of the microenvironment along the reaction course. Two fluorescent sensors have been considered: 1,1‐dicyano‐4‐(4′‐dimethylaminophenyl)‐1,3‐butadiene) and pyrene. In this article, we will show that using these two different fluorescent probes allow the detection of MMA polymerization in miniemulsion. The results will be compared with a classical NMR method. This method could be easily adapted to different monomers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel excimer fluorescence method for monitoring polymerization: 1. Polymerization of methyl methacrylate

An excimer is formed by the association of an excited molecule with another molecule in its ground state. Such an excimer is characterized by a broad structureless fluorescence which is shifted to longer wavelengths compared to the fluorescence spectrum of the isolated molecule. Intramolecular excimer fluorescence has been observed in solutions of pyrene-labelled alkanes such as 1,3-bis-(1-pyrene)propane and 1,10-bis-(1-pyrene)decane.We have measured the solvent-viscosity dependence of the intensity ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ for solutions of these pyrene-labelled alkanes in mixed solvents made of ethyl acetate and glycerol tripropionate. Here F_M and F_D are, respectively, the fluorescence intensity of the unassociated pyrene groups and that of the intramolecularly formed pyrene excimers. We have found that for each of the two pyrene-labelled alkanes, the ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ increases with the increase in solvent viscosity. Further, we have shown that by adding a trace amount of 1,3-bis-(1-pyrene)propane or 1,10-bis-(1-pyrene)decanee to a polymerizing system, we can measure the ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ to monitor in situ the polymerization reaction. polymerization;     

Vibrational spectroscopic investigation of light‐induced polymerization process of epoxy resin,polytetrahydrofuran and spirobislactone

The light‐induced polymerization process of bisphenol F diglycidyl ether (BFDGE), 5,5′‐dicarboxylic‐7,7′‐dioxo‐2,2′‐spirodi(benzotetrahydrofuran) (DCSBL) and polytetrahydrofuran (pTHF‐250) was studied. 4‐[(2‐Hydroxytetradecyl)oxy]phenyl‐phenyliodoniumhexafluoroantimonate, camphorquinone and ethyl 4‐dimethylaminobenzoate were used as a photoinitiator system. The polymerization process was induced by light and monitored using Fourier transform infrared spectroscopy. A novel combination‐initiation polymerization process was proposed: first, cationic copolymerization of BFDGE and pTHF‐250 was initiated by the photoinitiator system and heat was released by this polymerization; then, copolymerization of BFDGE and DCSBL was induced by that heat while pTHF‐250 served as an anionic initiator. Copyright © 2007 Society of Chemical Industry     

Nanocomposite polymer electrolytes by in situ polymerization of methyl methacrylate: For electrochemical applications

Hybrid materials, which combine properties of organic–inorganic materials, are of profound interest owing to their unexpected synergistically derived properties and are considered as innovative advanced materials promising new applications in many fields such as optics, electronics, ionics and mechanics. Inorganic fillers are added to polymers in order to increase some of the properties of the compounds. These hybrid polymeric materials are replacing the pristine polymers due to their higher strength and stiffness. In the present work, studies concerning the preparation of poly (methylmethacrylate) [PMMA] and the nanocomposites PMMA/SiO₂, PMMA/TiO₂ are reported. These nanocomposite polymers were synthesized by means of free radical polymerization of methylmethacrylate, further “sol–gel” transformation‐based hydrolysis and condensation of corresponding alkoxide was used to prepare the inorganic phase during the polymerization process of MMA. Electrolytes were synthesized based on these nanocomposite polymers and have shown superior properties as compared to conventional polymer electrolytes. The nanocomposites and the nanocomposite polymer electrolytes (NPEs) with different lithium salts were investigated through an array of techniques including FTIR and calorimetry along with the electrochemical and rheological techniques. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

In situ polymerization of aniline on acrylamide grafted cotton

In this article, polyaniline (PANI)/cotton composite were prepared by in situ polymerization on the grafted cotton. First, acrylamide was grafted onto cotton cellulose using a radical graft polymerization process and some influencing factors were studied. Then polyaniline/cotton conductive composite fabrics were prepared by chemical in situ polymerization on the grafted cotton. The influences of the concentration of ammonium persulfate, aniline, hydrochloric acid, and the reaction time to the conductivity and K/S of composite fabric were studied. By contrasting, graft brought on an improvement of about one order of magnitude to the conductivity of composite fabric. The strength, TG, FTIR‐ATR, and SEM of prepared fabric were measured. The thermal stability and tear strength of composite fabric reduced, whereas PANI exhibited a rough but uniform, coherent PANI coating on surface of cotton fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Excimer fluorescence as a probe of miscibility in styrene copolymer blends

The miscibility of styrene-alt-maleic anhydride (SMA) and a series of styrene-acrylonitrile (SAN) copolymers in blends with either PMMA or PVC were examined by fluorescence and FTIR spectroscopic techniques. In the case of the alternating copolymer intra-molecular excimer formation is precluded and changes in the excimer/monomer fluorescence intensity (I_E/I_M) reflect changes in the amount of inter-chain excimer formation. The value of I_E/I_M in blends, therefore, provides a sensitive measure of phase separation (miscibility). In the case of the acrylonitrile copolymers the I_E/I_M of the blend had to be corrected to account for intra-molecular excimers formed between adjacent chromophores in the SAN. These results compared favourably with observed frequency shifts in the phenyl C—H out-of-plane bend (～700 cm^?1).     

Effects of in situ esterification on the performance of carboxyl functionalized rubber‐modified epoxy film adhesives

Epoxy‐based film adhesive formulations were developed with 10 wt % solid carboxyl functional rubber. Due to the high rubber content and resulting viscosity restrictions, the rubber could not be prereacted with the epoxy before hot‐melt filming. Therefore, an esterification catalyst was used to perform this reaction in situ before the epoxy curing reactions. The performance of this adhesive system is compared to that of one without the esterification catalyst. A significant difference in the flow characteristics was observed with incorporation of the esterification catalyst, but only small variations in mechanical performance were found. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 728–734, 2000     

Cellulose nanocrystals (CNCs) reinforced acrylic pressure- sensitive adhesives (PSAs) prepared via miniemulsion polymerization

In this study, poly (n-butyl acrylate-co-2-ethyl hexyl acrylate) (P(nBA-co-2EHA)) pressure sensitive adhesives (PSAs) were successfully synthesized in the presence of cellulose nanocrystals (CNCs) via in-situ miniemulsion polymerization. First, the CNCs were prepared via acid hydrolysis of cellulose microcrystals (CMCs) at various temperatures, 42–54 °C, and characterized using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) apparatus. The results showed that hydrolysis of MCCs at 45 °C resulted in CNCs with a well-defined aspect ratio, average length of 206 nm and thickness of 3.9 nm, and the highest crystallinity. Adding further CNC to the copolymer adhesive enhanced the mean particle size of the composite latex and decreased the glass-rubber transition temperature (T_g) of the copolymer matrix. Molecular weights and viscoelastic properties of the resultant PSAs were determined using gel permeation chromatography (GPC) and dynamic mechanical thermal analysis (DMTA), respectively. Adhesion performance of the neat and reinforced PSAs containing 1–5 wt% CNCs was evaluated at room temperature. The results showed that the incorporation of CNCs up to 4 wt% in the copolymer adhesive increased the shear resistance by 518%, peel strength by 176% and probe tack by 13%, while further addition, 5 wt%, lowered the adhesion performance due to a lack of surface wettability.     

聚合工艺对丙烯酸酯乳液胶粘剂性能的影响

主要研究了聚合工艺对丙烯酸酯乳液胶粘剂性能的影响 通过对乳液胶粘剂的各种性能测试,发现3种聚合方法中,种子乳液聚合法制备的乳液胶粘剂的综合性能较为理想 采用种子乳液聚合法,最佳聚合工艺为:单体的滴加时间4h、聚合温度50℃、搅拌速率80 r/min     

Influence of thread geometry on the performance of retaining anaerobic adhesives

The main aim of this work is to study the influence of the geometry of screws on torsion tests when they are retained with adhesives. The geometry of different types of screw threads has been studied, measuring theoretical and real length values to determine the stress undergone by the thread when tightened and/or retained by anaerobic adhesives. Three kinds of joints are subjected to a torsion test to determine their loosening torque. According to their torque, joint loosening load as well as generated stress can be calculated. When tightened, the real contact area is observed to be lower than the theoretical area, and real stresses are therefore higher than the theoretical ones. The same can be observed when only adhesive is applied; the real bonded area is lower than the theoretical, while higher real stresses than theoretical are observed. When adhesive and tightening are combined, the stress due to the influence of the adhesive is calculated, since the strength ratio attributable to either friction or adhesion remains unknown. These can only be determined through the measurement of real thread dimensions.     

Investigations into the cumene hydroperoxide-based cure chemistry of anaerobic adhesives

Anaerobic adhesives polymerise rapidly, by a free radical mechanisms, when confined between two closely fitting metal surfaces to form tough solvent and heat resistant material. Anaerobic adhesives are typically based on methacrylate monomers and are predominantly used for the sealing and retaining of metallic objects. Transition metal ions on the substrate surface play a key role in the cure chemistry, catalytically decomposing hydroperoxides, such as cumene hydroperoxide, present in the adhesive to generate free radicals capable of initiating polymerisation. This study investigates the ability of lower and higher oxidation states of copper and iron to decompose cumene hydroperoxide, and also investigates the influence of saccharin, maleic acid and adhesive accelerators on this process.     

Benzodioxoles as alternative coinitiators for radical polymerization in a model‐dental adhesive resin

This study evaluated the effectiveness of benzodioxole derivatives as coinitiators of radical polymerization in a model‐dental adhesive resin. To compose the adhesive resin, a monomer mixture based on 50 wt % of Bis‐GMA, 25 wt % of TEGDMA, and 25 wt % of HEMA was used. Camphorquinone (CQ) 1 mol % was used as a photoinitiator to initiate polymerization. 1,3‐Benzodioxole (BDO) and piperonyl alcohol (PA) were used as coinitiators at 0.25, 0.5, 1, 2, 4, 8, and 16 mol % level. In addition, tertiary amine, ethyl 4‐dimethylamino benzoate (EDAB) was used as coinitiator in the control group. Some physical, chemical, and mechanical properties of the polymer formed in the experimental adhesives were evaluated using the kinetics of polymerization, sorption and solubility, flexural strength, and elastic modulus tests. The results indicated that BDO and PA were effective coinitiators in the photoinitiator system based on CQ. Comparisons between the benzodioxoles derivative coinitiators and EDAB showed similar performance in the kinetics of polymerization and flexural strength. For water sorption and solubility evaluation, BDO and PA demonstrated significantly more sorption of water and less solubility than the EDAB control group. The findings suggest that BDO and PA were feasible alternatives to conventional amine as coinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013