CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅰ

Controlled release of TDI and hence the cure characteristics of several blocked TDI with HTPB are reported. The reactions were followed through viscosity measurements as a function of time and temperature under the catalytic influence of triethylamine. The effect of nature of substituents present on the end capping substrate, temperature, solvent, basicity of catalyst and kinetics thereon have been studied.

Determination of toluene diisocyanate in synthetic-rubber track by ion chromatography with ultraviolet detection after alkaline suppressor

In the present work, a novel analytical method was proposed for the determination of toluene diisocyanate （TDI） in syntheticrubber track by ion chromatography （IC） coupled with an ultraviolet detector setting at 212 nm. TDI can be hydrolyzed to toluene diamine （TDA） which can be separated by cation-exchange IC easily. The optimum IC separation was performed on an IonPac CS12A column （150 mm ×4.0 mm） using 20 mmol L^-1 sodium sulfate, 10 mmol L^-1 sulfuric acid and 10% acetonitrile as eluent. It was found that a higher signal response of TDA could be obtained under alkaline condition. A suppressor was used to change the acidic eluent into alkaline one. 0.8 mol L^-1 potassium hydroxide was chosen as the optimum regeneration eluent. With the added suppressor and regenerant, signal response was magnified by about 16 times and lower limit of detection （LOD, 0.13 μg L^-1） was obtained. Within-day relative standard deviation （R.S.D.） was less than 3.6%. The recoveries of TDI spiked in synthetic-rubber track samoles were 96.4-110.6%.

Kinetics of the decomposition of dimethylhexane-1,6-dicarbamate to1,6-hexamethylene diisocyanate

The kinetics of the decomposition of dimethylhexane-1,6-dicarbamate to 1,6-hexamethylene diisocyanate was studied. A consecutive reaction model was established and the reaction orders for the two steps were confirmed to be 1 and 1.3 by the integral test method and the numerical differential method, respectively. The activation energies of the two steps were （56.94 4±5.90） kJ·mol^-1 and （72.07±3.47） kJ·mol^-1 with the frequency factors exp（ 12.53±1.42） min^- 1 and （ 14.254±0.84） tool^-0.33. L^0.33·min^-1, respectively. Based on the kinetic model obtained, the progress of the reaction can be calculated under given conditions.

~1H NMR analysis of the tolylene-2,4-diisocyanate-methanol reaction

Tolylene-2,4-diisocyanate（2,4-TDI） 1 reacts with methanol through two simultaneous paths in the polyurethane reaction,which involve two different intermediates-tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-carbamatic-4-isocyanate 3,and the final product is tolylene-2,4-dicarbamate 4.The-CH_3 chemical shifts in benzene ring in compounds 1,2,3 and 4 can be easily tested and well distinguished,through which those four compounds are quantified and their kinetics are investigated.It shows that four rate constants for the tolylene-2,4-diisocyanate-methanol reaction in CCl_4 at 50℃are k_1=9.6×10^（-2）h^（-2）mol^（-2）min^（-1）, k_2=1.4×10^（-2）h^（-2）mol^（-2）min^（-1）,k_3=4.0×10^（-3）h^（-2）mol^（-2）min^（-1）,k_4=1.4×10^（-3）h^（-2）mol^（-2）min^（-1）.（k_1 is the reaction rate constant from compounds 1 to 2;k_2 is the reaction rate constant from compounds 1 to 3;k_3 is the reaction rate constant from compounds 3 to 4;k_4 is the reaction rate constant from compounds 2 to 4）.

DIBUTYLTIN DILAURATE-CATALYZED DIISOCYANATE COUPLING—GRAFTING OF POLY(ETHYLENE GLYCOL)ONTO NANO-SILICA SURFACE THROUGH A ONE-STEP PROCEDURE

Grafting polymer glycols onto nano-silica surface through one-step procedure was investigated.The major characteristic of this procedure is that all the materials and reagents(silica,PEG,TDI,DBTDL,solvent)required for grafting were added simultaneously into the reaction vessel.TDI and DBTDL were used as coupling agent and catalyst,respectively. The products were characterized by FTIR,TGA,elemental analyses and TEM,giving evidence for successful grafting of PEG.Possible mechanism of this grafting was studied and two grafting processes were proposed.The process through which the grafting proceeds depends on the reaction temperature.Effect of molecular weight of PEG on grafting was also investigated.

Non-phosgene synthesis of hexamethylene-1,6-diisocyanate from thermal decomposition of hexamethylene-1,6-dicarbamate over Zn–Co bimetallic supported ZSM-5 catalyst

A non-phosgene route for the synthesis of hexamethylene-1,6-diisocyanate(HDI) was developed via catalytic decomposition of hexamethylene-1,6-dicarbamate(HDC) over Zn–Co bi-metallic supported ZSM-5 catalyst.The catalyst was characterized by FTIR and XRD analyses. Three solvents dioctyl sebacate(DOS), dibutyl sebacate(DBS) and 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF_4) were investigated and compared; DOS gave better performance. The catalytic performances for thermal decomposition of HDC to HDI using DOS as solvent were then investigated, and the results showed that, under the optimized reaction conditions, i.e.,10 wt%concentration of HDC in DOS, 250 °C temperature, 60 min reaction time, 83.8% yield of HDI had been achieved over Zn–Co/ZSM-5. Decomposition of the intermediate hexamethylene-1-carbamate-6-isocyanate(HMI) over Zn–Co/ZSM-5 in DOS solvent was further studied and the results indicated that yield of HDI from HMI reached to 69.6%(98.6% HDI selectively) at 270 °C, which further increased the yield of the total HDI(HDI_(tol)) to as high as 95.0%. Recycling of catalyst showed that HDI and HMI yield slightly decreased, and by-product yield increased after the catalyst was reused for 4 times. At last possible reaction mechanism was proposed.

CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅱ

Cure characteristics of hydroxyl terminated polybutadiene (HTPB) prepolymer with avariety of blocked toluene diisocyanate (TDI) in the presence of triethylamine (TEA) andchloroacetic acid catalyst are reported. Phenol, thiophenol, p-chloropheno1, p-nitrophenol,p-cresol, resorcinol, naphthols, caprolactam and butylated-hydroxytoluene were used as blockingagents. Viscosity measurements have been carried out using a mixture of HTPB and blocked TDIin cyclohexanone in the presence of the catalysts at 50℃ and 60℃ using Haake rotational vis-cometer. Viscosity measurements have also been carried out with 50% solids such as ammonium sulphate along with HTPB and TDI adduct.

The Curing for Modified Vinyl Ester Resin by Hexamethylene Diisocyanate and Its Influence on Performances

The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found to be a reactive agent for MVER and can contribute to the toughness of MVER.Based on present experiment results,the crosslinking mechanism of MVER and HDI system is very similar to that of PU.The FTIR result shows the-NCO of HDI can react with the-OH of MVER.The microstructure of material prepared by MVER and HDI was characterized by NMR,and it was revealed that the unique microstructure leads to the good performances.The different content of HDI has an influence on the microstructure,and the microstructure gradually reduces the toughness and mechanical performances of the MVER cured with increasing concentration of reactive curing agent(HDI).This feature is consistent with a maximum in toughness as a function of the additive(HDI)content,followed by a rapid deterioration in toughness at higher concentrations.The toughness exhibits the maximum at such an HDI concentration(20wt%).Therefore,the special curing agent(HDI)and reactive mode is very important to the microstructure and mechanical properties of material.Furthermore,there should be other reactions which contribute to the curing and microstructure of the material,which needs the further research.

Synthesis and Properties of Organic-Inorganic Hybrid Porous Polymers Obtained with Click Addition Reactions of Thiol-Functionalized Random Type Silsesquioxane by and Diacrylate or Diisocyanate Compounds

Organic-inorganic hybrid network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquioxane (SQ109) and alkyl diacrylate or diisocyanate compounds. Thiol-ene reaction of SQ109 and 1,4-butanediol diacrylate (BDA) successfully yield porous polymer in toluene initiated by azobis(isobutyronitrile) (AIBN) at 60°C. Morphology of the porous polymers was composed by connected globules, and the diameter of the globules decreased with increasing in the monomer concentration of the reaction system. By contrast, the reaction with 1,6-hexanediol diacrylate or 1,5-hexadiene yielded homogeneous clear gels. Thermal analyses of SQ109-BDA porous polymers indicated that thermal degradation of ester groups of BDA in the polymer network occurred at around 300°C. The porous polymer was also obtained by the reaction using a photo-initiator (Irugacure184) at room temperature, and showed higher Young’s modulus than the corresponding porous polymer obtained with the reaction with AIBN due to the small size of the globules. Young’s modulus of SQ109-BDA porous polymer increased with increasing in the monomer concentration of the reaction systems. Thiolisocyanate addition reactions between SQ109 and hexamethylene diisocyanate (HDI) or methylenediphenyl 4,4’-diisocyanate (MDI) were investigated to obtain network polymers. The reactions in toluene yielded the corresponding homogeneous clear gels. By contrast the reactions in a mixed solvent of toluene (50 vol.%) and N,N-dimethylformamide (50 vol.%) produced porous polymers. The morphology of the porous polymers was composed by connected globules or aggregated particles. The size of globules and particles in the SQ109-HDI porous polymers was larger than those in the SQ109-MDI porous polymers. Thermal degradation of SQ109-HDI and SQ109-MDI porous polymers started at round 260°C and showed endothermic peak at around 350°C derived from degradation of thio-urethane bond.

An efficient green route for hexamethylene-1,6-diisocyanate synthesis by thermal decomposition of hexamethylene-1,6-dicarbamate over Co3O4/ZSM-5 catalyst： An indirect utilization of CO2

The utilization of CO2 as raw material for chemical synthesis has the potential for substantial economic and green benefits. Thermal decomposition of hexamethylene-1,6-dicarbamate （HDC） is a promising approach for indirect utilization of CO2 to produce hexamethylene-1,6-diisocyanate （HDI）. In this work, a green route was developed for the synthesis of HD1 by thermal decomposition of HDC over Co3O4/ZSM-5 catalyst, using chlorobenzene as low boiling point solvent. Different metal oxide supported catalysts were prepared by incipient wetness impregnation （IWI）, PEG-additive （PEG） and deposition precipitation with ammonia evaporation （DP） methods. Their catalytic performances for the thermal decomposition of HDC were tested. The catalyst screening results showed that Co3O4/ZSM-525 catalysts prepared by different methods showed different performances in the order of Co3O4/ZSM-5 25（PEG） 〉 Co3O4/ZSM-525（IWI） 〉 Co3O4/ZSM-525（DP）. The physicochemical properties of Co3O4/ZSM- 52s catalyst were characterized by XRD, FTIR, N2 adsorption-desorption measurements, NH3-TPD and XPS. The superior catalytic performance of Co3O4/ZSM-52S（PEG） catalyst was attributed to its relative surface content of Co3 ＋, surface lattice oxygen content and total acidity. Under the optimized reaction conditions： 6.5% HDC concentration in chlorobenzene, 1 wt% Co3O4/ZSM-525（PEG） catalyst, 250℃ temperature, 2.5 h time, 800 ml.min 1 nitrogen flow rate and 1.0 MPa pressure, the HDC conversion and HDI yield could reach 100% and 92.8% respectively. The Co3O4/ZSM-525（PEG） catalyst could be facilely separated from the reaction mixture, and reused without degradation in catalytic performance. Furthermore, a possible reaction mechanism was proposed based on the physicochemical properties of the Co3O4/ZSM-5 25 catalysts.

Polychlorinated biphenyls in the atmosphere of Taizhou,a major e-waste dismantling area in China

PM2.5, total suspended particles （TSP） and gas phase samples were collected at two sites of Talzhou, a major e-waste dismantling area in China. Concentrations, seasonal variations, congener profiles, gas-particle partitioning and size distribution of the atmospheric polychlorinated biphenyls （PCBs） were studied to assess the current state of atmospheric PCBs after the phase out of massive historical dismantling of PCBs containing e-wastes. The average ∑38PCBs concentration in the ambient air （TSP plus gas phase） near the e-waste dismantling area was （12,407 ± 9592） pg/m^3 in winter, which was substantially lower than that found one decade ago. However, the atmospheric PCBs level near the e-waste dismantling area was 54 times of the reference urban site, indicating that the impact of the historical dismantling of PCBs containing e-wastes was still significant. Tri-Penta-CBs were dominant homologues, consisting with their dominant global production. Size distribution of particle-bound PCBs showed that higher chlorinated CBs tended to partition more to the fine particles, facilitating its long range air transportation.

Occurrence and congeners specific of poiychlorinated biphenyls in agricultural soils from Southern Jiangsu, China

A total of 198 agricultural soil samples were collected from Zhangjiagang and Changshu in Southern Jiangsu for analysis of 13 polychlorinated biphenyls （PCBs） in order to assess the levels of pollution, sources, area distribution, and potential risk for the environment. All methods were rigorously tested and an adequate quality control was ensured. Only one site had no PCBs residues, and the highest total PCBs concentration in the surface soils was 32.83 ng/g. The average concentration in all the soil samples was 4.13 ng/g, signaling low-level pollution. Tetra-, penta-, and hexa-chlorinated biphenyls were dominant species in soil samples, accounting for more than 75% of ∑PCBs in the soil samples. PCB118 was the most abundant congener in all the samples. The PCB118 was about 20% of ∑PCBs. The soil organic matter content showed only a weak correlation with the levels of all PCB congeners, in which a better correlation was noted for the more volatile lighter PCB congeners than for the heavier homologues. To a certain extent, the sources and land use seemed to influence the levels of PCBs.

Levels and distributions of polychlorinated biphenyls in sewage sludge of urban wastewater treatment plants

Concentrations of polychlorinated biphenyls （PCBs） have been measured in sewage sludge samples from 8 urban wastewater treatment plants in Beijing, China. The PCB congeners were analyzed by isotope dilution high resolution gas chromatography/high resolution mass spectrometry method. The concentration of PCBs ranged from 65.6 to 157 ng/g dry weight （dw）, with a mean value of 101 ng/g dw. The dioxin-like PCB WHO-TEQs （World Health Organization-Toxic Equivalents） of the sludge were lower than 1 pg /g dw. Consequently, all the concentrations of PCBs in sludge samples were below the upper limit for land application according to the Chinese legislation law for agriculture use. The PCB homologue profiles in sludge samples were dominated by tri-CBs and tetra- CBs. Similar distributions have been found in one of the Chinese PCB commercial products. The patterns of dioxin-like and indicator congeners observed in this study were quite similar in all samples. The predominant congener for dioxin-like and indicator PCBs were PCB-118 and PCB-28, respectively, while PCB-126 had the highest TEQ value.

Biphenyl Ferulate from Glehnia littoralis

From the underground parts of Glehnia littoralis Fr. Schmidt ex Miquel (Umbelliferae), a new compound named glehnilate was obtained. Its structure was determined by analysis of its spectral data.

Impact of poly chlorinated biphenyl (Aroclor 1254) and vitamin C on antioxidant system of rat ventral prostate

Aim: To evaluate the effect of polychlorinated biphenyls (PCB) and vitamin C on ventral prostatic antioxidant system in adult male rats. Methods: A group of 20 adult male rats were administered ip Aroclor 1254 in corn oil at a dose of 2 mg·kg-1·day-1 for 30 days. Ten control rats were administered only the vehicle. After 30 days the treated rats were divided at random into 2 sub-groups of 10 animals each. One sub-group received vitamin C at a dose of 500 mg·kg-1·day-1 for 10 days. The other group was maintained as Aroclor 1254 control. Twenty-four hours after the last treatment the rats were killed by decapitation. Ventral prostatic homogenate was prepared and used for the estimation of enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) and hydrogen peroxide (H2O2), lipid peroxidation (LPO) and prostatic acid phosphatase. The serum levels of total T3, total T4, TSH, testosterone and estradiol were also assayed. Results: The body weight and ventral prostatic weight were reduced in PCB treated rats. The activities of SOD, CAT, GST and acid phosphatase were decreased while the levels of H2O2 and lipid peroxidation were increased in the ventral prostate of PCB treated rats. Administration of vitamin C restored these parameters. Serum levels of thyroid hormones, estradiol and testosterone were decreased in PCB treated animals. Administration of vitamin C restored the thyroid hormone levels. Conclusion: PCB induces oxidative stress and decreases the antioxidant enzymes in the ventral prostate of adult male rats; the effects could be reversed by the administration of vitamin C.

Synthesis and biological evaluation of nitric oxide-releasing sixalkoxyl biphenyl derivatives as anticancer agents

A series of novel nitric oxide-donating sixalkoxyl biphenyl derivatives （14a-1） were synthesized by coupling furoxan with alkoxyl biphenyl skeleton using amino acids as the spacers, and their cytotoxicity against HepG2 cells in vitro were evaluated by MTT method. It was found that 14c, 14d, 14f, 14i, 14j and 14k showed more potent cytotoxic activities than control 5-fluorouracil. NO release assay of target compounds indicated that the maximum amount of NO released by most active compounds 14c and 14j was about 6 × 10^-2 μmol/L, whereas 14a and 14h with very weak activity only released NO of 1 × 10^-2 μmol/L.

Synthesis,Characterization and Fluorescence Properties of Europium,Terbium Complexes with Biphenyl-4-Carboxylic Acid and o-Phenanthroline

Two series of solid complexes of europium and terbium with biphenyl 4-carboxylic acid and phen were synthesized and characterized in this report. Their elemental analysis, molar conductivities and TG-DTA studies indicate that the complexes have the composition of Eu(phen)L3·1/2H2O, Eu0.5RE0.5(phen) L3·1/2H2O; Tb (phen) L3·H2O and Tb0.5 RE0.5(Phen)L3·1/2H2O. (RE = Y3+, La3+ and Gd3+; L = biphenyl 4-carboxylic acid; phen = o-Phenanthroline). The studies of their IR, UV 1H NMR and molar conductivities demonstrate that biphenyl 4-carboylic acid is bounded with RE (III ) ion. Rare earth ions coordinate with two nitrogen atoms of phen molecules directly in these rare earth complexes. The fluorescence spectra and fluorescence lifetimes of the rare earth complexes show that the fluorescent intensity and lifetime of a series of europium complexes are longer than those of the series of terbium complexes as having the some ligands. There are better fluorescent intensity and lifetime of hetero-nuclear rare earth complexes than homo-nuclear rare earth complexes for europium complexes. The fluorescence emission intensity of Eu3 + is raised by inert fluorescent rare earth ions (Y3+ , Gd3+ and La3+ ), but in Tb3+ hetero-nuclear rare earth complexes the intensity of Tb3+ ions are quenched by the inert fluorescent rare earth ions.

A QSRR Study on the Chromatographic Retention Indices of Hydroxylated Polychlorinated Biphenyls

Hydroxylated Polychlorinated Biphenyls （HO-PCBs） are the metabolite of polychlorinated biphenyls and have drawn much attention because they have hazard on human health and ecosystems. Molecular connectivity index calculation has been performed for 19 HO-PCB compounds. A number of statistically based parameters have been extracted. Linear relationship between chromatographic retention index （RI） and the molecular connectivity index of 15 compounds in the training set has been established by multiple linear regression method. The other 4 HO-PCBs are used as the external test set. The result shows that the parameters can be well used to express the quantitative structure-retention relationship （QSRR） of HO-PCBs. Good stability and predictive ability have been demonstrated by leave-one-out cross-validation and the external test set.