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.

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%.

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.

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.

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.

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.

Ameliorating end-product inhibition to improve cadaverine production in engineered Escherichia coli and its application in the synthesis of bio-based diisocyanates

Cadaverine is an important C5 platform chemical with a wide range of industrial applications.However,the cadaverine inhibition on the fermenting strain limited its industrial efficiency of the strain.In this study,we report an engineered Escherichia coli strain with high cadaverine productivity that was generated by developing a robust host coupled with metabolic engineering to mitigate cadaverine inhibition.First,a lysine producing E.coli was treated with a combination of radiation(ultraviolet and visible spectrum)and ARTP(atmospheric and room temperature plasma)mutagenesis to obtain a robust host with high cadaverine tolerance.Three mutant targets including HokD,PhnI and PuuR are identified for improved cadaverine tolerance.Further transcriptome analysis suggested that cadaverine suppressed the synthesis of ATP and lysine precursor.Accordingly,the related genes involved in glycolysis and lysine precursor,as well as cadaverine exporter was engineered to release the cadaverine inhibition.The final engineered strain was fed-batch cultured and a titer of 58.7 g/L cadaverine was achieved with a yield of 0.396 g/g,both of which were the highest level reported to date in E.coli.The bio-based cadaverine was purified to>99.6%purity,and successfully used for the synthesis of polyurethane precursor 1,5-pentamethylene diisocyanate(PDI)through the approach of carbamate decomposition.

The influence of the NCO/OH ratio and the 1,6-hexanediol/ dimethylol propionic acid molar ratio on the properties of waterborne polyurethane dispersions based on 1,5-pentamethylene diisocyanate

1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5-pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transfonn infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffiraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU.

Preparation and Formation Mechanism of Porous Polyurea by Reaction of Toluene Diisocyanate with Water and Its Application as Adsorbent for Anionic Dye Removal

A novel and easy one-step protocol for preparation of a new porous material, polyurea （PPU）, is reported, which is accomplished through a precipitation polymerization of toluene diisocyanate （TDI） in mixed solvent of H20-acetone without need for surfactant and porogen. Effects of TDI concentration, mechanical stirring, solvent composition and TDI addition rate on PPU structure are studied. Surface morphology and pore structure of PPU are characterized by scanning electron microscopy and Hg intrusion. Chemical structure of the PPU polymer is investigated using NMR, XRD and FTIR. Mechanism of pore formation is discussed. The obtained PPU is used as adsorbent for anionic dyes adsorption investigation. Two anionic dyes, remazol brilliant blue R and acid fuchsine, are tested. The results indicate that the as-prepared PPU is of high performance in dye adsorption and recycled use. This study provided therefore a facile route to the preparation of a novel and attractive adsorbent candidate for removal of anionic dyes from wastewaters.

Zn-Co bimetallic supported ZSM-5 catalyst for phosgene-free synthesis of hexamethylene–1,6–diisocyanate by thermal decomposition of hexamethylene–1,6–dicarbamate

A set of mono-and bimetallic（Zn-Co） supported ZSM-5 catalysts was first prepared by PEG-additive method. The physicochemical properties of the catalysts were investigated by FTIR, XPS, XRD, N2adsorption-desorption measurements, SEM, EDS and NH3-TPD techniques. The physicochemical properties showed that the Zn Co2O4 spinel oxide was formed on the ZSM-5 support and provided effectual synergetic effect between Zn and Co species for the bimetallic catalyst. Furthermore, bimetallic supported ZSM-5 catalyst exhibited weak, moderate and strong acidic sites, while the monometallic supported ZSM-5 catalyst showed only weak and moderate or strong acidic sites. Their catalytic performances for thermal decomposition of hexamethylene–1,6–dicarbamate（HDC） to hexamethylene–1,6–diisocyanate（HDI） were then studied. It was found that the bimetallic supported ZSM-5 catalysts,especially Zn-2Co/ZSM-5 catalyst showed excellent catalytic performance due to the good synergetic effect between Co and Zn species, which provided a suitable contribution of acidic sites. HDC conversion of 100% with HDI selectivity of 91.2% and by-products selectivity of 1.3% could be achieved within short reaction time of 2.5 h over Zn-2Co/ZSM-5 catalyst.

Effect of Ipomea carnea Jacq. flowers on hematological changes in toluene diisocyanate-induced inflammation in Wistar rats

AIM： To investigate the active chloroform fraction of the ethanol extract oflpomoea carnea flowers on hematological changes in toluene diisocyanate-induced inflammation in Wistar rats. METHOD： Except for the control group, all of the rats were sensitized with intranasal application of 5 μL of 10% toluene diiso- cyanate （TDI） for 7 days. One week after second sensitization, all of the rats were provoked with 5 ~tL of 5% TDI to induce airway hypersensitivity. After the last challenge, blood and bronchoalvelor lavage （BAL） fluid were collected and subjected to total and differential leucocytes count. Flash chromatography was performed on the most active chloroform fraction to isolate an individual component. RESULTS： Treatment with the ethanolic extract and its chloroform fraction at an oral dose of 200 mg·kg^ -1 showed a significant decrease in circulating neutrophil and eosinophil in blood and BAL as compared with standard dexamethasone （DEXA）. The structure of the compound obtained from chloroform fraction oflpomea carnea was elucidated as stigmast-5, 22-dien-3β-ol on the basis of spectral data analysis. CONCLUSION： The chloroform fraction was found to be more effective to suppress airway hyper reactivity symptoms, and de- creased count of both total and differential inflammatory cells.

Slightly Cross-Linked Polyrotaxanes Made by Linking α-Cyclodextrins Entrapped in Polyrotaxanes Using Hexamethylene Diisocyanate

In this study polyrotaxane （PR）-based triblock copolymers were first synthesized via the atom transfer radical polymerization （ATRP） of N-isopropylacrylamide initiated with the self-assembly of a distal 2-bromoisobutyryl end-capped Pluronie 17R4 with a varying amount of a-cyclodextrins （a-CDs） in the presence of CuCI/PMDETA at 25 ℃ in aqueous solution. The a-CDs entrapped on the copolymer chain were then linked with hexamethylene diisocyanate to give rise to novel slightly cross-linked polyrotaxanes （SCPRs） in DMF at 45 ℃. The structures of the PR-based triblock copolymers and SCPRs were characterized by 1H NMR, 13C CP/MAS, GPC and TGA analy- ses. The number-average molecular weight of the resulting SCPRs was nearly three and five times of their precursor after linking with a low polydispersity index range of 1.08--1.28. The thermo-responsive transition of both PR-based supramolecular polymers in aqueous solution was demonstrated by turbidity measurements and the self-aggregated morphologies were also evidenced by TEM observations.

Physical-Rheological Properties and Performances of Rejuvenated(Styrene-Butadiene-Styrene)Asphalt with Polymerized-MDI and Aromatic Oil

Traditional asphalt rejuvenators,like aromatic oil(AO),are known to be effective in improving the low-temperature properties and fatigue performances of aged SBS(styrene-butadiene-styrene)modified asphalt(SBSMA)binders and mixtures.However,these rejuvenators inevitably compromise their high-temperature properties and deformation resistances because they dilute asphalt binder but do not fix the damaged structures of aged SBS.In this study,a highly-active chemical called polymerized 4,4-diphenylmethane diisocyanate(PMDI)was used to assist the traditional AO asphalt rejuvenator.The physical and rheological characteristics of rejuvenated SBSMA binders and the moisture-induced damage and rut deformation performances of corresponding mixtures were comparatively evaluated.The results showed that the increasing proportion of AO compromises the hightemperature property and hardness of aged SBSMA binder,and an appropriate amount of PMDI works to compensate such losses;3%rejuvenator at mass ratio of AO:PMDI=70:30 can have a rejuvenated SBSMA binder with a high-temperature performance similar to that of fresh binder,approximately at 71.4°C;the use of AO can help reduce the viscosity of PMDI rejuvenated SBSMA binder for improving its workability;PMDI can help improve the resistance of AO rejuvenated SBSMA binder to deformation,especially at elevated temperatures,through its chemical reactions with aged SBS;moisture induction can enhance the resistance to damage of rejuvenated mixtures containing AO/PMDI or only PMDI;and the rejuvenator with a mass ratio of AO:PMDI=70:30 can lead the rejuvenated mixture to meet the application requirement,with a rut depth of only 2.973 mm,although more PMDI can result in a higher resistance of rejuvenated mixtures to high-temperature deformation.

Synthesis and Characterization of HDI/MDI-Polycarbonate Urethanes

A novel polycarbonate urethane was synthesized by the two-stage solution process of diisocyanates with polycarbonate diols(PCDL),in which PCDL,1,4-butanediol(BD) and mixture of 4,4 -methylenediphenyl diisocy-anate and hexamethylene diisocyanate(HDI) were soft segment,chain extender and rigid segment,respectively.The structures were characterized by using FTIR and 1H-NMR.The thermoanalysis and mechanical properties of products were measured by means of DSC,TG and other systems.The result shows that an import...

The Influence of Aziridine on the Aging of Composite Solid Rocket Propellant

Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the influence of the aziridine bonding agents family on the propellant aging. Aging of the prepared propellant samples was conducted as follows: 1. Four samples, one free of bonding agents, and three containing aziridine based bonding agents MAPO,HX-752, MAT4 were aged at 65°C. 2. Another four samples based on HX-752, MAT4 with different curing agents were aged at 65°C. The measured mechanical properties of the free bonding agent propellant samples were very far from the specifications and this illustrates the importance of the bonding agents in both the preparation and the aging phases.The prepared bonding agent 'MAT4' gave remarkable improvements of the mechanical properties comparing with HX-752 and MAPO. The aziridine bonding agents family inhibited the rate of decomposition of the propellant during the aging periods and supported the propellant matrix against decomposition at the elevate temperatures. Using of HMDI as curing agent gave slight better mechanical properties to the IPDI.

Synthesis and properties of UV curable polyurethane acrylates based on two different hydroxyethyl acrylates

Two kinds of UV curable polyurethane acrylate oligomers （PUPA and PUCA） were synthesized via the addition reaction between isophorone diisocyanate （IPDI） and polyethylene glycol monoacrylate （PEA6） or polycaprolactone modified hydroxyethyl acrylate （PCLA2）. The structures of PUPA and PUCA were characterized by Fourier transform infrared spectroscopy （FT-IR）, IH nuclear magnetic resonance （^H NMR）, gel permeation chromatography （GPC） and differential scanning calorimeter （DSC）, and the thermal stability and dynamic mechanical thermal properties of their cured films were measured by thermogravimetric analysis （TGA） and dynamic mechanical analysis （DMA）, respectively. The viscosity of the oligomers and mechanical properties of the cured films were also studied. The results show that both oligomers have narrow molecular weight distribution. The viscosity of PUPA is 2.310 Pa.s at 25 ℃, while that of PUCA is： up to 3.980 Pa-s. The UV cured PUPA and PUCA films have homogeneous phase structure, and the PUCA film shows higher glass transition temperature and storage modulus. Furthermore, the PUCA film possesses better mechanical properties than PUPA, while the latter shows better alkali resistance.

Surface Modification of Commercial Aromatic Polyamide Reverse Osmosis Membranes by Crosslinking Treatments

Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.

Valorization of Kraft Lignin as Thickener in Castor Oil for Lubricant Applications

It is known that large amounts of residual lignin are generated in the pulp and paper industry.A new alternative for Kraft lignin valorization,which consists of first a chemical modification using a diisocyanate and then the efficient dispersion in castor oil to achieve stable gel-like systems,is proposed in this work.Rheological properties and microstructure of these materials were determined by means of small amplitude oscillatory shear tests and viscous flow measurements and atomic force microscopy observations,respectively.Moreover,both standardized penetration tests and tribological assays,usually performed in the lubricant industry,were carried out to evaluate the performance characteristics as lubricating greases.Linear viscoelasticity functions are affected by the lignin/diisocyanate ratio and thickener concentration.The thermorheological response evidenced a softening temperature of around 105°C.The microstructure of these gel-like dispersions is composed of interconnected thin fibers,homogeneously distributed in castor oil.Moreover,the NCO-functionalized lignin gel-like dispersions studied show lower friction coefficients than traditional lubricating greases.

Influences of Diamines on the Morphologies and the Chemical, Thermal, and Mechanical Properties of Polyurethane-Imide Elastomers

Polyurethane-imide elastomers (PUIEs) are formed from isocyanate, polyol, acid anhydride, and diamine by liquid polymerization. Unfortunately, many of the diamines have rarely been applied to the formation of PUIEs. Hence, investigating the effect of diamines on PUIEs remains a challenge in polymer chemistry. Herein, PUIEs prepared from 4,4'-diphenylmethane diisocyanate (MDI), polytetramethylene glycol (Mw: 1000), pyromellitic dianhydride, and aromatic diamines (such as p-phenylene diamine, 4,4'-oxydianiline, and 1,3-bis(4-aminophenoxy)benzene), and aliphatic diamines (such as 1,2-ethylene diamine, 1,6-hexamethylene diamine, and 1,12-dodecamethylene diamine) were synthesized by liquid polymerization. The morphologies and the chemical, thermal, and mechanical properties of the various PUIEs were investigated. The obtained elastomeric sheets were characterized in terms of the following tests and methods: solubility and swelling tests, X-ray diffraction and differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis, tensile tests, nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy, contact angle microscopy, and scanning electron