Surface Modifications Produced by N2 and O2 RF Plasma Treatment on a Synthetic Vulcanized Styrene-Butadiene Rubber

A low-pressure gas RF plasma-treatment has been used to improve the adhesion of a synthetic vulcanized rubber to polyurethane adhesive as an environmentally friendly alternative surface treatment to the conventional chemical treatments. A sulfur vulcanized styrene-butadiene rubber (R2) containing a noticeable amount of zinc stearate and paraffin wax (both providing a lack of adhesion) in its formulation was used. Two different gases (oxygen and nitrogen) were used to generate the RF plasma, which was performed at 50 Watt for 1–15 min. The modifications produced on the R2 rubber surface by the RF plasma treatments were assessed by using advancing and receding contact angle measurements, ATR-IR spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Force Microscopy (SFM), and Scanning Electron Microscopy (SEM). Adhesion evaluation was obtained from T-peel tests of joints produced between plasma treated R2 rubber and a polyurethane adhesive. The plasma treatment produced a decrease in advancing and receding contact angle values on R2 rubber, irrespective to the gas used to generate the RF plasma. The treatment with RF plasma produced the partial removal of hydrocarbon moieties from the rubber surface and the generation of oxygen moieties. An increase in surface roughness was also produced. The degree of oxidation and the amount of hydrocarbon-rich layer removed from the R2 rubber surface was more important by treating with oxygen plasma. The treatment of rubber in oxygen plasma for 1 minute was enough to noticeably increase adhesion of R2 rubber to polyurethane adhesive. However, an extended treatment (15 min.) was needed when nitrogen plasma was applied to R2 rubber. The loci of failure in the joints produced between the plasma treated R2 rubber and the polyurethane adhesive was assessed by using ATR-IR spectroscopy. A mixed failure (partially adhesional and partially cohesive failure in the rubber) in the joints produced with plasma treated R2 rubber joints was always obtained.     

Adhesive properties of rubbers with promoters based on modified silica filler

The influence of new adhesion promoters on the strength of bonding between unfilled rubber materials based on synthetic isoprene rubber SKI-3 and a brass-plated metal cord was studied. The synthesized adhesion promoters are silica fillers modified with cobalt, nickel, or a combination of cobalt and nickel, and they contain on their surface a lower number of ions of metals with variable valency compared to industrial cobalt stearate. It was shown that, among the synthesized adhesion promoters, silica fillers modified with cobalt are the most promising.     

轮胎橡胶多组分分析方法的研究

轮胎橡胶物证是涉车案件中常见物证,对于相关案件的侦破具有重要的物证价值。本文根据轮胎橡胶组分体系的特点,设计了以大型仪器为主线的多组分分析方案。所选用的仪器设备及方法有:裂解气相色谱仪(Py-GC)、裂解气相色谱与质谱联用仪(Py-GCMS)、差示扫描量热仪(DSC)、热重分析仪(TGA)、原子吸收分光光度计(AAS)、化学法;实验中,测试了轮胎橡胶的胶型、配合剂定性(防老剂定性、促进剂定性、其他助剂定性)、玻璃化温度,焓值,高聚物含量、配合剂含量、炭黑含量、无机填料(盐酸不溶物、氧化锌含量、二氧化硅含量)、硫含量等十三个测试项目;并将已知配方的硫化胶理论值与测试样品结果比对分析。分析结果表明:建立的系列方法的测试结果准确、可靠,可以为轮胎橡胶的分析鉴别提供技术支持。     

胶粉/热塑性塑料共混材料的研究

以胶粉及通用塑料PP和LLDPE为原料,研究了原料种类、相容剂等对胶粉/热塑性塑料共混材料性能的影响,制得了性能较好的共混材料。通过热分析和扫描电镜对制得的共混材料进行分析表征,表明胶粉和LLDPE有较好的相容性及较强的结合力。     

Synthesis and Application of Epoxidized Natural Rubber

Abstract

North Vietnamese NR latexes were successfully epoxidized using peracetic acid at moderate temperature and pH range. The epoxide contents of pure epoxidized natural rubber (ENR) are from 5 to 70 mol%. The ENR products were characterized and determined by spectral and thermal analysis besides the chemical titration. Conditions of longlasting or excessive temperature, or high acidic pH led to side ring opened products, proved easily by IR, ¹H-NMR, and DSC analysis. The ENR were vulcanized using a semiefficient system. The epoxidation increased the adhesion between rubber and tire cord and metal. This effect becomes stronger beyond 25 mol% and tends to be limited at over 60 mol%. The ENRs were used to formulate special-purpose adhesives. The shear strength of the adhesive ranges from 32 to 45 kg/cm² for bonding rubber to nylon and rubber to metal, respectively.     

间甲钴黏合体系在轮胎骨架材料中的黏合机理研究

为验证与进一步探索黏合树脂及钴盐对轮胎与镀铜钢丝帘线的增黏作用机理,选取传统黏合树脂R80与2种新型黏合树脂HT1005和H620,通过对2种新型黏合树脂的结构分析、橡胶硫化特性、静态T抽出测试与力学性能测试,并设计了一种新的黏合层强度测试方法与黏合层表征方法,进行机理探索,得出如下结论:含有羟基的极性黏合树脂在橡胶硫化时,会由于与非极性天然橡胶的极性差异产生的热力学不相容从而产生自动相分离,向橡胶与镀铜钢丝的界面层进行迁移汇集,且极性越高迁移能力越强,产生一个介于橡胶与镀铜钢丝之间的树脂富集层.因为黏合树脂交联反应温度为140℃左右,会在天然橡胶硫化反应时发生同步交联反应,黏合树脂形成的网络模量高于橡胶硫化网络,会增强镀铜钢丝与橡胶之间的黏合层强度,并形成一个镀铜钢丝与橡胶之间的模量过渡层,进一步增强黏合层.且极性越强,树脂网络交联程度与橡胶硫化网络交联程度越接近,增黏效果越好;钴盐会活化橡胶中的S,使更多的S迁移到镀铜钢丝表面从生成更多硫化亚铜键,增强黏合.     

主成分回归-络合滴定法测定混合金属离子

提出了用络合滴定法测定混合金属离子.以汞膜电极为指示电极,银-氯化银电极为参比电极,以标准EDTA溶液滴定混合金属离子溶液.采集-系列指定电位点处滴定剂的体积,并以主成分回归法处理滴定数据.利用本文方法对铜、锌、铅、钻混合溶液进行了测定,结果满意.     

Synthetic Layered Silicate as a Carrier for Liquid Ingredients for the Rubber- and Tire Industry

We propose the use of novel materials based on synthetic calcium silicate hydrate (C S H) for the rubber- and tire industry. We found that the synthetic silicate belongs to the family of layered calcium silicate hydrates. Due to its layered structure and inert surface it easily adsorbs liquid components of rubber compounds, such as bis(triethoxysilylpropyl) tetrasulfide (TESPT) and liquid polysulfide (LP). Then, in processing, the C S H can smoothly release these components. The water, trapped in the material's gallery layers, plays the role of a catalyst in the silane coupling on silica's surface. In addition, we used this silicate as a component in promoter systems in order to improve adhesion stability between a brass-coated steel cord and rubber. The application of the calcium silicate hydrate as an inert substrate for the promoter system allowed the development of materials that have comparable adhesion strength with most commercial promoters.     

Surface stoichiometry of zinc sulfide and its effect on the adsorption behaviors of xanthate

ABSTRACT: In this paper, the surface stoichiometry, acid-base properties as well as the adsorption of xanthate at ZnS surfaces were studied by means of potentiometric titration, adsorption and solution speciation modeling. The surface proton binding site was determined by using Gran plot to evaluate the potentiometric titration data. Testing results implied that for stoichiometric surfaces of zinc sulfide, the proton and hydroxide determine the surface charge. For the nonstoichiometric surfaces, the surface charge is controlled by proton, hydroxide, zinc and sulfide ions depending on specific conditions. The xanthate adsorption decreases with increasing solution pH, which indicates an ion exchange reaction at the surfaces. Based on experimental results, the surface protonation, deprotonation, stoichiometry and xanthate adsorption mechanism were discussed.     

电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%~10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。     

Potentiometric determination of N-acetylglucosaminyl-N′-acetylmuramyl-L-alanyl-D-isoglutamine and the starting materials and intermediates for its synthesis

The conditions for the potentiometric acidimetric titration in nonaqueous solutions of N-acetylglucosaminyl-N′-acetylmuramyl-L-alanyl-D-isoglutamine (GMCP), its sodium salt, N-acetylglucosaminyl-N′-acetylmuramic acid, the γ-benzyl esters of the trifluoroacetate of D-isoglutamine, of N-tert-butoxycarbonyl-D-isoglutamine, and of N-tert-butoxycarbonyl-L-alanyl-D-isoglutamine, and also the o-nitrophenyl esters of N-tert-butoxycarbonyl-D-isoglutamine γ-benzyl ether and of N-tert-butoxycarbonyl-L-alanine have been investigated. Methods have been developed for the analysis of milligram amounts of GMDP and of the starting materials and intermediates for its synthesis by potentiometric titration with a ～0.025–0.030 N nitromethane solution of perchloric acid. The relative error of the determinations amounts to ±1.5% and the residual standard deviation to 1.3%.     

Apparent dissociation constants of polycarboxylic acids in presence of polycations

The dissociation behaviour of poly(acrylic acid) and poly(ethylene-alt-maleic acid) has been investigated by both classical potentiometric titration and colloid titration as an alternative way. In the case of colloid titration, the monovalent counterions are assumed to be replaced by the oppositely charged polycation in the course of titration, so that the total concentration of anionic groups of the polycarboxylic acid is determined. As a consequence the apparent dissociation constants determined by polyelectrolyte complex formation do not depend on the degree of dissociation. In contrast to this finding, potentiometric titration is known to result in apparent dissociation constants which decrease with increasing degree of dissociation. The release of protons from the acid groups of the polycarboxylic acids is promoted by the complex formation with the strong cationic polyelectrolyte.     

A combination of synchronous fluorescence spectroscopy with chemometric treatment and internal standards in non-aqueous potentiometric titrations of fulvic acids

The acid properties of a soil fulvic acid (sfua) were characterized by potentiometric titration with tetrabutylammonium hydroxide in two non-aqueous solvents with high acid—base resolution power N,N-dimethylformamide (DMF) and acetonitrile. Synchronous fluorescence spectroscopy (SyF) was also used to monitor directly the sfua status during the potentiometric titration in DMF. The potentiometric titration curves showed no clear end-point and the analysis of the sets of spectra obtained at increasing neutralization degree, with a self-modeling curve resolution method (SIMPLISMA), revealed the existence of two components with featureless concentration profiles. Internal standards (maleic, salicylic and p-hydroxylbenzoic acids) were used to determine the amounts of acid groups with different acid strengths in the two non-aqueous solvents. It was shown that the variations observed in the SyF spectra sets of the internal standards are not correlated with those observed in the sfua data. The splitting of the sfua groups in the non-aqueous titration curves seems to be forced artificially depending on the standards used.     

全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对两个不同品位试样分别进行了11次平行测定,相对标准偏差(RSD)均小于1%。在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的加标回收实验,碳酸根的加标回收率在99.4%~100%。与传统的酸碱滴定法相比,全自动电位滴定法方便、快捷,同时方法测定结果准确、可靠、精密度高,适合大批量样品快速分析。     

Adsorption of valeric acid from aqueous solution onto activated carbons: role of surface basic sites

Adsorption of valeric acid was studied on two activated carbons of different origins, wood and bituminous coal. The effect of oxidation on the adsorption uptake was investigated. Both initial samples were oxidized with nitric acid, which caused the introduction of a significant number of oxygen-containing groups onto the carbon surface. Boehm titration, potentiometric titration, thermal analysis, and sorption of nitrogen were used for detailed surface characterization. Valeric acid adsorption from aqueous solution was measured at 333 K. The calculated isotherms showed a good fitting to the Freundlich equation. The capacity coefficients revealed a direct correlation with the number of basic groups present on the surface. The amount of valeric acid adsorbed at its low concentration is dependent on the number of basic groups, whereas at high concentration the amount adsorbed depends on the volume of micropores smaller than 10 A, where the adsorption potential is the strongest.     

Recycling ground tire rubber (GTR) scraps as high‐impact filler of in situ produced polyketone matrix

A sustainable procedure for recycling powdered rubber coming from scrap tires (ground tire rubber [GTR]) is proposed as based on the dispersion in polyketone (PK) matrix, obtained in situ by CO/ethylene copolymerization. Three types of catalysts are used operative in solvents of different polarities. The catalyst productivity and the hybrids morphology are evaluated and optimized to final composites features. The obtained products are characterized by scanning electron microscopy, atomic force microscopy, and solvent extractions in order to investigate the occurrence and the extent of interactions between PK macromolecular chains and the GTR components; and their effects on the final properties were tested by differential scanning calorimetry, thermogravimetric analysis, and rheological measurements. For comparison purpose, a composite with GTR included into the matrix through blending is prepared. The results evidenced the key role exerted by the catalyst that, when operative in apolar solvent (able to swell the rubber phase), provides composites with good interfacial adhesion and breaking up of the particles with beneficial effects on final properties particularly thermal features and processability. Copyright © 2014 John Wiley & Sons, Ltd.     

Visible-light-enhanced interactions of hydrogen sulfide with composites of zinc (oxy)hydroxide with graphite oxide and graphene

Composites of zinc(oxy)hydroxide-graphite oxide and of zinc(oxy)hydroxide-graphene were used as adsorbents of hydrogen sulfide under ambient conditions. The initial and exhausted samples were characterized by XRD, FTIR, potentiometric titration, EDX, thermal analysis, and nitrogen adsorption. An increase in the amount of H(2)S adsorbed/oxidized on their surfaces in comparison with that of pure Zn(OH)(2) is linked to the structure of the composite, the relative number of terminal hydroxyls, and the kind of graphene-based phase used. Although terminal groups are activated by a photochemical process, the graphite oxide component owing to the chemical bonds with the zinc(oxy)hydroxide phase and conductive properties helps in electron transfer, leading to more efficient oxygen activation via the formation of superoxide ions. Elemental sulfur, zinc sulfide, sulfite, and sulfate are formed on the surface. The formation of sulfur compounds on the surface of zinc(oxy)hydroxide during the course of the breakthrough experiments and thus Zn(OH)(2)-ZnS heterojunctions can also contribute to the increased surface activity of our materials. The results show the superiority of graphite oxide in the formation of composites owing to its active surface chemistry and the possibility of interface bond formation, leading to an increase in the number of electron-transfer reactions.     

Pyrolysis Gas Chromatography–Mass Spectrometry for the Characterization of Tire Marks for Forensic Analysis

Pyrolysis–gas chromatography–mass spectrometry was applied to the quantitative and comparative analysis of rubber samples collected from tire marks left on different types of road surfaces. Ten types of tires were used to create skid marks. It was observed that factors such as surface type, sampling method, and the place where the sample was taken revealed no influence on chemical composition of pyrolysate. Chemical analysis of the traces left on different types of substrates allowed one to distinguish between these traces, allocate samples to different rubber classes, and to assign the trace to a particular type of tire. Application of a simple, semi-quantitative method developed to describe the composition of the samples facilitated the distinction between samples. Furthermore, in most cases, tire marks showed great consistency with the rubber taken from the respective tires.     

Potentiometric determination of the total acidity and concentration of citric acid in wines

The method of potentiometric titration with a copper electrode is used for the determination of the total acidity and concentration of citric acid (CA) in identifying the adulteration of wines. The procedure is suitable for the determination of citric acid in wines in the range from 0.1 to 3.5 g/L in the presence of 30-fold amounts of tartaric, acetic, malic, succinic acids and a 10-fold amount of oxalic acid after the separation of organic carboxylic acids on an AV-17-8 anion exchanger. The procedure was developed and certified for the potentiometric determination of the mass fraction of citric acid in table wines and wine materials with an error not exceeding 20%. The criteria (mass fraction of citric acid, the percentage of citric acid in the total acidity, and the shape of the curves of potentiometric titration) were proposed for revealing the adulteration of the acid composition of wines.     

Intrinsic adhesion properties of poly(vinyl pyrrolidone) to pharmaceutical materials: humidity effect

Poly(vinyl pyrrolidone) (PVP) is widely used for bioengineering and pharmaceutical applications, and its adhesion characteristics are critical. When used as a binder in pharmaceutical granulation, it covers the resultant granules and governs their surface properties. The intrinsic adhesion forces of PVP toward common hydrophobic (magnesium stearate) and hydrophilic (lactose) pharmaceutical materials have been studied as a function of relative humidity (RH). The effect of RH on adhesion force was more significant for the PVP/hydrophilic material than the PVP/hydrophobic material. Adhesion was lowest between 20 and 40% RH, and it increased at RH above 40% and below 20%. This is likely to be due to the development of capillary and triboelectrification forces, respectively. In a nano-indentation experiment using a silicon tip at room temperature, the PVP surface underwent a glass transition at 70% RH. This result suggests that surface softening contributes to the increased PVP adhesion at RH above 70%. To adjust the adhesion properties of PVP, humidity control should be an essential part of research and development. Effect of humidity on the adhesion forces between PVP and lactose (LT) or magnesium stearate (MS).