Curing mechanism of alkaline phenolic resin with organic ester

To study the curing mechanism of alkaline phenolic resin with organic ester, three esters were chosen to react with three systems - alkaline phenolic resin, potassium hydroxide aqueous solution containing phenol, and potassium hydroxide aqueous solution. The variations of pH, heat release and gel pH during the reactions were monitored and measured. Infrared spectroscopy （IR） and thermal gravity analysis （TG） techniques were used to characterize the curing reaction. It was found that organic ester is only partial y hydrolyzed and resin can be cured through organic ester hydrolysis process as wel as the reaction with redundant organic ester. The sequential curing mechanism of alkaline phenolic resin cured by organic ester was identified as fol ows： a portion of organic ester is firstly hydrolyzed owing to the effect of the strong alkaline; the gel is then formed after the pH decreases to about 10.8-10.88, meanwhile, the redundant organic ester （i.e. non-hydrolysis ester） starts the curing reaction with the resin. It has also been found that the curing rate depends on the hydrolysis velocity of organic ester. The faster the hydrolysis speed of the ester, the faster the curing rate of the resin.

Curing mechanism of TDE-85/MeTHPA epoxy resin modified by polyurethane

Diglycidyl 4,5-epoxy tetrahydro phthalate/methyl tetrahydrophthalic anhydride （TDE-85/MeTHPA） epoxy resin modified by polyurethane （PU） was prepared with 1,4-butanediol （1,4-BDO）, trimethylol propane （TMP） and polyurethane prepolymer synthesized by polypropylene glycol and toluene diisocynate. Chemical reaction and curing mechanism of this system were discussed by incorporating the results of infra spectrum analysis. The results indicate that the epoxy polymeric network I is obtained by the curing reaction between TDE-85 and MeTHPA, while the PU polymeric network II is obtained by the chain-extended and crosslinking reaction between 1,4-BDO, TMP and polyurethane prepolymer（PUP）. The graft chemical bonds are formed between polymer networks I and II that therefore increase the degree of blend and compatibility between epoxy polymer and PU.

Curing mechanism of furan resin modified with different agents and their thermal strength

The curing mechanism of furfuryl alcohol and urea-formaldehyde furan resins was investigated using infrared spectroscopy(IR) technique.The curing productions of urea-formaldehyde furan resins modified with different agents(i.e.sorbitol,polyester polyol,phenol and acetone) and the productions of incomplete curing were characterized by differential thermal analysis(DTA) and thermal gravity analysis(TG).The results indicate that except for polyester polyol,the other modifiers have little effect on the thermal strength of urea-formaldehyde furan resin.Furthermore,the thermal strength can be improved at a temperature of higher than 550℃.

Curing reaction and mechanism of phenol-formaldehyde novolac resins for foundry

In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMTA were studied by differential scanning calorimetry(DSC). Based on the data calculated by the Kissinger equation and the Crane equation, a thermocuring dynamic model was established, from which the process conditions, activation energy, reaction kinetics equation and a f irst-order reaction of the curing reactions were derived.

THE MECHANISM OF CURE REACTION OF 4,4'-DIAMINODIPHENYL METHANE WITH TETRAGLYCIDYL 4,4'-DIAMINODIPHENYL METHANE EPOXY

The cure reaction of tetraglycidyl 4,4'-diaminodiphenyl methane (TGDDM) epoxy resin with 4,4'-diaminodiphenyl methane (DDM) has been studied by using DSC. Instead of one exothermic peak, two exothermic peaks, indicative of a complex reaction mechanism, are shown in the DSC curve of TGDDM-DDM mixtures in nonisothermal cure experiments when the content of DDM is lower than stoichiometric ratio. The result of the kinetic analysis of the cure reaction shows that the activation energy of the lower temperature exotherm peak is about 56 kJ/mol and that of the higher temperature exotherm peak is about 136 kJ/mol. The lower temperature cure reaction peak can be attributed to the primary amine-epoxide and secondary amine-epoxide reactions, and the higher temperature cure reaction peak can be attributed to the epoxide-hydroxy reaction under catalysis of tertiary amine in the TGDDM epoxy resin. Because the network density of the cured epoxy resin is determined by these two reactions, the content of DDM has little effect on the glass transition temperature of cured epoxy resin.

Study on influence factors of cement-stabilized soil compressive strength

The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.

Recent Advances in Flame Retardant Bio-Based Benzoxazine Resins

Benzoxazines have attracted wide attention from academics all over the world because of their unique properties.However,most of the production and preparation of benzoxazine resins depends on petroleum resources now,especially bisphenol A-based benzoxazine.Therefore,owing to the environmental impacts,the development of bio-based benzoxazines is gaining more and more interest to substitute petroleum-based benzoxazines.Similar to petroleum-based benzoxazines,most of bio-based benzoxazines suffer from flammability.Thus,it is necessary to endow bio-based benzoxazines with outstanding flame retardancy.The purpose of this review is to summarize the latest advance in flame retardant bio-based benzoxazines.First,three methods of the synthesis of bio-based benzoxazines are introduced briefly.Furthermore,the curing mechanism of benzoxazine and the effect of branched chains on the curing behavior are also discussed and summarized.Subsequently,this review focuses on fully bio-based benzoxazines,partly bio-based benzoxazines,and bio-based benzoxazine composite materials in terms of flame retardancy as well as thermal stability and some other special properties.Finally,we give a brief comment on the challenges and prospects of the future development of flame retardant bio-based benzoxazines.

Buildings and civil engineering works-Sealants-Determination of changes in cohesion and appearance of elastic weatherproofing sealants after exposure of statically cured specimens to artificial weathering and mechanical cycling

Foreword ISO(the International Organization for Standardization)is a worldwide federation of national standards bodies(ISO member bodies).The work of preparing International Standards is normally carried out through ISO technical committees.Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee.

Phthalonitrile Resins Derived from Vanillin: Synthesis, Curing Behavior, and Thermal Properties

Vanillin was used as sustainable source for phthalonitrile monomer synthesis, and allyl/propargyl ether moieties were introduced to improve the processability at the minimal cost of thermal properties. The synthesis route was optimized to minimize side-reactions and simplify post-processing, and the monomers were obtained in high purity and good yields. The curing behavior, mechanism, and processability of the monomers were studied, and the thermal properties of cured polymers were evaluated. Of the two monomers, the allyl ether-containing one exhibited a wide processing window of 185 °C, and was mainly cured into phthalocyanine and linear aliphatic structures through self-catalytic curing process. Also, the glass transition temperature was higher than 500 °C. In contrast, the propargyl ether-containing monomer could only be partially cured, and heat resistance was found to be compromised. Compared with traditional petroleum-based phthalonitrile resins, the biobased monomers could be cured without the addition of catalysts, and improvement in processability was achieved at no cost of thermal performances.

Robust UV/moisture dual curable PDMS-microcapsule-silica functional material for self-healing,antifouling,and antibacterial applications

Polydimethylsiloxane containing methacryloyloxy and methoxy silane groups(MAPDMS)-microcapsule-SiO_(2)(MPMS)functional materials were prepared by constructing micro-nano hierarchical structures on the surface of MAPDMS matrix.Herein,MAPDMS@1,1-stilbene-modified hydrolyzed polyglycidyl methacrylate/graphene oxide/dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride(MAPDMS@PGMA_(m)/GO/QC18)self-healing microcapsules with compact multi-shell structure were synthesized and combined with nano-SiO_(2)to construct the hierarchical structures.Furthermore,ultraviolet(UV)/moisture dual curing mode was introduced into deep curing reaction and efficient self-healing reaction of the MPMS.The results show that the introduction of UV/moisture dual curing mode and micro-nano hierarchical structure gives MPMS functional materials excellent mechanical properties,antifouling properties,self-healing properties,antibacterial properties.The shear strength and tensile strength of MPMS increase from 3.32 and 4.26 MPa of MAPDMS to 3.81 and 5.06 MPa,respectively.Its static contact angle increases from 115.9°of MAPDMS to 156.5°,its slide angle decreases from 68.5°of MAPDMS to 7.8°,respectively.The antifouling performance of MPMS against seawater,soy sauce,juice,coffee,protein,other contaminants is effectively improved compared with MAPDMS matrix.At the same time,the tensile strength and elongation at break of MPMS after healing reach 98.22%and 96.57%of those in original state,respectively.In addition,the antibacterial rates of MPMS against Escherichia coli and Staphylococcus aureus reach 99.85%and 100%,respectively.The MPMS prepared in this paper is expected to be widely used in marine antifouling,pipeline network,anti-icing,microfluidics,wearable devices,medical devices,electrochemical biosensors,other fields.