Synthesis,cationic polymerization and curing reaction with epoxy resin of 3,9‐di(p‐methoxybenzyl)‐1,5,7,11‐tetra‐oxaspiro(5,5)undecane

A new spiro ortho carbonate, 3,9‐di(p‐methoxybenzyl)‐1,5,7,11‐tetra‐oxaspiro(5,5)undecane was prepared by the reaction of 2‐methoxybenzyl‐1,3‐propanediol with di(n‐butyl)tin oxide, following with carbon disulfide. Its cationic polymerization was carried out in dichloromethane using BF₃‐OEt₂ as catalyst. The [¹H], [¹³C]NMR and IR data as well as elementary analysis of the polymers obtained indicated that it underwent double ring‐opening polymerization. The polymerization mechanism is discussed. The curing reaction of bisphenol A type epoxy resin in the presence of the monomer and a curing agent was investigated. DSC measurements were used to follow the curing process. In the case of boron trifluoride‐o‐phenylenediamine (BF₃‐OPDA) as curing agent, two peaks were found on the DSC curves, one of which was attributed to the polymerization of the epoxy group, and the other to the copolymerization of the monomer with the isolated epoxy groups or homopolymerization. However, when BF₃‐H₂NEt was used as curing agent, only one peak was present. IR measurement of the modified epoxy resin with various weight ratios of epoxy resin/monomer was performed in the presence of BF₃‐H₂NEt as curing agent. The results demonstrate that the conversion of epoxy group increases as the content of monomer increases. The curing process and the structure of the epoxy resin network are discussed. © 2000 Society of Chemical Industry     

UV‐initiated free radical and cationic photopolymerizations of acrylate/epoxide and acrylate/vinyl ether hybrid systems with and without photosensitizer

Various properties of UV‐initiated acrylate/epoxide and acrylate/vinyl ether hybrid photopolymerizations with and without photosensitizer in the presence of free radical and cationic‐type photoinitiators have been determined by dynamic mechanical thermal analysis (DMTA), calorimetric analysis (photodifferential scanning calorimetry, photo‐DSC; and differential scanning calorimetry), and scanning electron microscopy. DMTA experiments revealed that the UV curing of hybrid systems may produce interpenetrating polymer networks. Photo‐DSC analyses indicated that the acrylates polymerized faster than the epoxide and vinyl ether in the hybrid systems; the addition of a photosensitizer, isopropylthioxanthone (ITX), increased the polymerization rate of the epoxide and vinyl ether in the hybrid systems. SEM analysis confirmed that the free radical system seemed to be significantly affected by oxygen inhibition, while the cationic and hybrid systems were not nearly inhibited by oxygen; the presence of photosensitization produced by the addition of ITX enhanced the surface curing of the hybrid systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1473–1483, 2004     

Kinetic analysis of curing behavior of diglycidyl ether of bisphenol A with imidazoles using differential scanning calorimetry techniques

The curing kinetics and mechanisms of diglycidyl ether of bisphenol A (DGEBA) using imidazole (H‐NI) and 1‐methyl imidazole (1‐MI) as curing agents are studied with differential scanning calorimetry (DSC) under isothermal (90–120°C) and dynamic conditions (50–250°C). The isothermal DSC thermograms of curing DGEBA with H‐NI and 1‐MI curing agents show two exothermic peaks. These peaks are assigned to the processes of adduct formation and etherification. These results indicate that there is no difference in the initiation mechanism of 1‐unsubstituted (H‐NI) and 1‐substituted (1‐MI) imidazoles in the curing reaction with epoxy resin. A kinetic analysis is performed using different kinetic models. The activation energies obtained from DSC scanning runs using the Ozawa and Kissinger methods are similar and in the range of 75–79 and 76–82 kJ/mol for DGEBA/H‐NI and DGEBA/1‐MI systems, respectively. These values compare well with the activation energies obtained from isothermal DSC experiments using the autocatalytic method (74–77 kJ/mol). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2634–2641, 2006     

Multifunctional formaldehyde resins as curing agent for epoxy resins

Formaldehyde resins (FR) at 1/1/2 molar ratios of monomers (Cl‐phenol/amino monomers/p‐formaldehyde) were synthesized under acid catalysis. The obtained resins were characterized using elemental analysis, FTIR and RMN spectroscopic methods, being used as crosslinking agents for epoxy resin formulations. The curing of epoxy resins with FR were investigated. The glass transition temperature (T_g) and decomposition behavior of crosslinked resins were studied by differential scanning calorimetry (DSC) and thermogravimetric (TGA) techniques. All DSC scans show two exothermic peaks, which implied the occurrence of cure reactions between epoxy ring and amine or carboxylic protons, in function of chemical structures of FR. The crosslinked products showed good thermal properties, high glass transitions, and low water absorption. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

乙烯基酯树脂固化条件及其复合材料的研究

研究了过氧化二苯甲酰(BPO)、过氧化二异丙苯(DCP)、过氧化苯甲酸叔丁酯(TBPB)3种固化剂对乙烯基酯树脂固化工艺的影响,并根据固化工艺制备出树脂浇铸体及其碳纤维复合材料。采用差示扫描量热(DSC)法研究了不同树脂固化体系的反应放热特性,采用扫描电镜(SEM)分析了浇注体的断面的表面形态。并对浇注体及复合材料进行了力学性能测试和热稳定性表征,结果表明制得的复合材料具有优良的力学性能和热稳定性。     

Preparation and characterization of printable solder resist inks based on hyperbranched polyester

Two novel solder resist inks containing hyperbranched epoxy resin (HBPE) for thermal curing and hyperbranched epoxy acrylate resin (HBPEA) for UV‐curing were introduced in this work. Different generations of HBPE and HBPEA were synthesized and their chemical structures were determined by FT‐IR. Both curing reactions were monitored under differential scanning calorimetry (DSC) and photo‐DSC. For HBPE, the curing temperature of 7th generation was only 91°C and for HBPEA, the curing duration of 7th generation was under 10 s. The thermal stabilities of cured resins were much more stable than linear resin, as the decomposition temperatures of HBPE and HBPEA were both over 400°C. The ink containing HBPE or HBPEA jetted by piezoelectric printer showed excellent accuracy and consistency of linewidth and the morphologies of cured pattern were observed through a stereo microscope. Other performances of solder masks were tested under China Printed Circuit Association (CPCA) standard (CPCA/JPCA 4306‐2011), which satisfy all requirements of printed circuit board soldering procedure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41805.     

Effects of processing conditions on the curing of a vinyl ester resin

The effects of temperature, initiator, and accelerator levels on the curing of an epoxy bisphenol‐A vinyl ester resin Derakane® 411‐45 (formulated with styrene) were investigated by gel‐time and exotherm‐peak measurements on bulk samples. It was observed that the gel time was reduced as the initiator or accelerator ratio increased. Except at higher contents of the accelerator, a small kinetic plateau was seen in the gel curve and a shift of the maximum exotherm toward high temperatures in the DSC curves. This was explained by the dual role played by the accelerator species. A regression analysis of all gel‐time data showed a dependence of 3/2 order in the accelerator and first order in the initiator concentrations. Thus, for this polymerization initiation system, the gel time can be predicted for any initiator and cobalt levels and at any temperature within the ranges studied. The effect of the initiator on the unreacted styrene and vinyl ester was also examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1146–1154, 2002; DOI 10.1002/app.10403     

Studies on Cure Kinetics of Diglycidyl Ether of 4,4′-Bisphenol/4,4′-Diaminobiphenyl Using the Advanced Isoconversional Method

The cure kinetics of a rigid-rod epoxy monomer, diglycidyl ether of 4,4′-bisphenol (DGEBP), and the curing agent with the similar rigid-rod group, 4,4′-diaminebiphenyl (DABP), was studied using an advanced isoconversional method (AICM). DGEBP/DABP curing system was carried out by means of differential scanning calorimetry (DSC). Three exothermic peaks were depicted by nonisothermal DSC studies: the first two peaks were attributed to the curing reaction, and the last peak was attributed to the decomposition of the cured epoxy resin. The LC phase transformation of the curing process was observed by PLM. Using AICM, the largest activation energy of the curing reaction of DGEBP/DABP system was obtained as 108 kJ/mol. It can also be learned that LC phase transformation of the curing process affects the reaction significantly.     

Kinetic study of radical polymerization. II. Solid‐state bulk polymerization of sodium methacrylate by differential scanning calorimetry

The solid‐state radical polymerization of sodium methacrylate was investigated. It was initiated by azobisisobutyronitrile, which was used as a radical initiator. Differential scanning calorimetry (DSC) was used to observe the endothermic and exothermic transitions during the polymerization reaction. Structural studies were performed with the DSC thermograms and Fourier transform infrared and ultraviolet–visible spectra, and all of the results confirmed the progress of the reaction. The obtained data revealed that the polymerization reaction proceeded completely with a 100% conversion. ΔH of this reaction was calculated with various amounts of the initiator, and the peak temperatures were determined at different heating rates. The activation energy (19.7 kcal mol^?1) was also obtained by the Kissinger method for this type of solid polymerization reaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1648–1654, 2003     

The effect of an anhydride curing agent,an accelerant,and non‐ionic surfactants on the electrical resistivity of graphene/epoxy composites

This study investigated different contents of an anhydride curing agent, an accelerant, and non‐ionic surfactants on the electrical resistivity of cured graphene/epoxy composites. The anhydride curing agent was hexahydrophthalic anhydride (HHPA), the accelerant was 2‐ethyl‐4‐methyl‐1H‐imidazole‐1‐propanenitrile (EMIP), and the non‐ionic surfactants were Triton X surfactants with different numbers of polyethylene oxide (PEO) groups (m) that influence the electrical resistivity of cured graphene/epoxy composites. During the curing process, differential scanning calorimetry (DSC) was used to determine the effects of the extent of the crosslinking for different contents of the curing agent and how different enthalpy (ΔH) on the electrical resistivity of the cured graphene/epoxy composites was then generated. The cured graphene/epoxy composite—which consisted of a 1 : 0.85 weight ratio of epoxy resin and anhydride, a 0.5 wt % accelerant, and a 13 wt % graphene powder—had a low electrical resistivity of 11.68 Ω·cm and a thermal conductivity of 1.7 W/m·K. In addition, the cured composites contained a 1.0 wt % polyethylene glycol p‐isooctylphenyl ether (X‐100) surfactant, which effectively decreased their electrical resistivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41975     

Frontal polymerization of a cyanate ester

Thermal frontal polymerization is an exothermic process that uses a propagating wave to polymerize monomers via an external heat source, such as a soldering iron, to initiate front propagation. Herein, for the first time, the curing of a cyanate ester via thermal frontal polymerization is described with two different external heat sources. However, issues of bubbling due to vaporization of the amine catalyst generally resulted in incomplete frontal polymerization when a soldering iron was used as the external heat source. To counter this issue, dual‐strip polymerization systems were used, wherein the heat from the exothermic polymerization of a free‐radical system was used to initiate the frontal polymerization of a cyanate ester system with an amine catalyst. As a result, complete frontal polymerization occurred. Additionally, the effect of the width of the acrylate strip and its impact on the front temperature, initial velocity, and steady‐state velocity of the adjacent cyanate ester system were studied. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Role of acrylic acid in the synthesis of core‐shell fluorine‐containing polyacrylate latex with spherical and plum blossom‐like morphology

The core‐shell fluorine‐containing polyacrylate latex was successfully synthesized by two‐stage semicontinuous emulsion copolymerization of methyl methacrylate (MMA), butylacrylate (BA), acrylic acid (AA), and dodecafluoroheptyl methacrylate (DFMA). The fluorine‐containing polyacrylate latex was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC). The effects of AA content on monomer conversion, polymerization stability, particle size, corsslinking degree, carboxyl groups distributions (latex surface, aqueous phase or buried in latex), as well as mechanical properties and water absorption rate of latex film were investigated. The obtained fluorine‐containing polyacrylate latex exhibited core‐shell structure with a particle size of 120–150 nm. The introduction of AA was beneficial for the increase of monomer conversion and the polymerization stability, and had little effects on the mechanical property of latex film. However, the hydrophilicity of AA made the water resistance of latex film get bad. With the increase of AA content, the carboxyl groups preferred to distribute on aqueous phase, and the possibility of homogeneous nucleation increased and more oligomers particles were formed. Moreover, the oligomers would distribute to the latex and continued to grow up, making the latex morphology changed from spherical to plum blossom‐like. The core‐shell latex had two T_g corresponding to the rubber polyacrylate core and hard fluorine‐containing polyacrylate shell, and the latex film possessed excellent thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42527.     

Epoxy‐Based Azopolymers with Enhanced Photoresponsive Properties Obtained by Cationic Homopolymerization

Azopolymers are highly versatile materials due to their unique photoresponsive properties. In this contribution, a novel azo‐modified epoxy network is synthesized by cationic homopolymerization with boron trifluoride monoethylamine (BF₃.MEA) complex as initiator. The effect of the addition of a fixed content of amino‐functionalized azo chromophore, Disperse Orange 3, into the polymer matrix is studied in detail. First of all, the thermal curing cycle is optimized by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) measurements. Then, the resulting bulk azo‐modified epoxy networks are characterized by means of thermogravimetric analysis (TGA), FTIR, DSC, UV–vis spectroscopy, and rheological measurements. Finally, the optical response of thin films of these materials is determined. The results evidence that azo‐modified epoxy networks obtained by cationic polymerization with optimized curing cycle display high T _g values, high maximum photoinduced birefringence, fast writing speed, and exceptionally high remnant anisotropy. Therefore, this material is a promising candidate to be used for optical storage applications.     

DSC analysis of epoxy molding compound with plasma polymer–coated silica fillers

Silica fillers were modified by plasma‐polymerization coating of 1,3‐diaminopropane, allylamine, pyrrole, 1,2‐epoxy‐5‐hexene, allylmercaptan, and allylalcohol using RF plasma (13.56 MHz). Modified fillers were then mixed with biphenyl epoxy resin, phenol novolac (curing agent), and optionally triphenylphosphine (catalyst) to prepare samples for DSC analyses. Some samples were also prepared from uncoated silica fillers and monomers used in plasma polymerization coating, instead of plasma polymer–coated silica fillers. Plasma polymer–coated silica fillers were characterized by FTIR, XPS, and water contact angle measurements. In DSC analyses, all samples with plasma polymer–coated silica fillers showed a large peak and an additional one or two small exothermic peaks when catalyst was added, compared to only one large peak with as‐received silica fillers. The large peak could be from epoxy–phenol novolac reaction in the presence of catalyst, whereas small reaction peaks were attributed to the chemical reaction between epoxy resin and functional moieties in the plasma polymer coating, such as amine, OH, and/or SH groups, as evidenced by FTIR and XPS analysis and contact angle measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2508–2516, 2003     

In situ FT‐IR and DSC investigation on the cure reaction of the dicyanate/diepoxide/diamine system

Cure reactions of a liquid aromatic dicyanate ester (1,1′‐bis(4‐cyanatophenyl)ethane, BEDCy) with a liquid bisphenol A epoxide (2,2‐bis(4‐glycidyloxyphenyl)propane, BADGE) and 4,4′‐diaminodiphenyl sulfone (DDS) were studied through correlation of the in situ FT‐IR spectroscopy and DSC in dynamic scanning mode. Before this system was examined, cure reactions of precursory systems of BADGE/DDS, BEDCy/BADGE and BEDCy/DDS were investigated separately. Cure reaction paths for each system are proposed. Some reactions in the precursory systems, such as polycyclotrimerization of dicyanate to form sym‐triazine and formation of alkyl isocyanurate, were not observed in the combined curing system BEDCy/BADGE/DDS. Four principal reaction paths are proposed for this curing system: (1) formation of oxazoline from the reaction between the epoxide and cyanate group; (2) reaction of epoxide with primary amine to form a hydroxyl group; (3) reaction of epoxide with the hydroxyl group to form an ether linkage; and (4) rearrangement of oxazoline to form oxazolidinone. Two distinct, but somewhat overlapping, exothermic peaks were observed on the DSC thermogram. The lower temperature peak on the DSC thermogram was primarily contributed by the first reaction path, whereas the higher temperature peak can mainly be attributed to the reaction paths 2, 3 and 4. © 2001 Society of Chemical Industry     

Comparative study of silicon‐containing cycloaliphatic epoxides between different chemical structures and curing mechanisms for potential light‐emitting diode encapsulation applications

The aim of this paper is to systematically investigate the curing behavior of three novel di‐ and trifunctional silicon‐containing cycloaliphatic epoxy resins by both anhydride and cationic ring‐opening polymerization methods as well as the viscoelasticity, thermal stability, water absorption and optical properties of the cured products. Differential scanning calorimetry curves show that, relative to anhydride curing, cationic polymerization can decrease the curing temperature to below 120 °C, and the reaction exothermic peaks become very narrow and sharp, exhibiting rapid curing characteristics at moderately low temperature. In addition, the differences between the anhydride and cationic curing methods bring about interesting variations in physical properties for the cured products which are well related to their chemical structures, polymerization mechanism, crosslinking density, segmental flexibility and inter‐segmental distance. The excellent transparency, rapid cationic curing rate, good thermal stability and high glass transition temperature of over 275 °C make this series of epoxy resins promising candidates for light‐emitting diode encapsulation applications. © 2012 Society of Chemical Industry     

超支化聚酰胺酯增韧增强环氧树脂的性能研究

以四氢甲基苯酐(MeTHPA)为固化剂,超支化聚酰胺酯(HBP)为增韧剂,制备了HBP/MeTHPA/环氧树脂(EP)固化体系。采用红外光谱(FT-IR)对HBP/MeTHPA/EP复合体系的固化机理进行了研究,并讨论了不同含量的HBP对固化体系热力学性能的影响。实验结果表明,HBP的加入会促进体系的固化反应;当w(HBP)=10%时力学性能最佳,冲击强度和拉伸强度分别增加了142.71%和34.44%,而玻璃化转变温度(Tg)有所下降,储能模量在玻璃态时均明显提高。     

Conductive epoxy/amine system containing polyaniline doped with dodecylbenzenesulfonic acid

We developed a conductive epoxy/amine system containing polyaniline doped with dodecylbenzenesulfonic acid (PAni.DBSA). The curing behaviors of diglycidyl ether of bisphenol A with triethylenetetramine (TETA), PAni.DBSA, and both amine compounds at different concentrations were investigated by differential scanning calorimetry (DSC). Epoxy/TETA systems containing PAni.DBSA presented two distinct exothermic peaks at 90°C due to the cure by TETA as a hardener and at 236°C related to PAni.DBSA as the curing agent. The presence of PAni.DBSA in the systems constituted by epoxy/hardener in stoichiometric proportions resulted in a decrease in the glass‐transition temperature of the epoxy matrix, as indicated by DSC and dielectric analyses. Electrical conductivity was determined in the epoxy/amine networks, with the TETA concentration kept constant and also in stoichiometric proportions of mixed hardener (TETA + PAni.DBSA) to epoxy resin. The last condition resulted in a higher electrical conductivity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:4059–4065, 2006     

Photopolymerization kinetics of an epoxy‐based resin for stereolithography

Curing reactions of photoactivated epoxy resins are assuming an increasing relevance in many industrial applications, such as coatings, printing, and adhesives. Besides these processes, stereolithography (SL) makes use of photoactivated resins in a laser‐induced polymerization for 3D building. The kinetic behavior of photocuring is a key point for full comprehension of the cure conditions occurring in the small zone irradiated by the laser beam during the building process. Furthermore, the kinetic analysis is very important to determine the cure time needed for part building in a stereolithographic equipment. The mechanisms involved in a cationic photopolymerization are complex compared with radical photopolymerization. In this paper the photoinitiated polymerization of a commercially available epoxy‐based resin for stereolithography (SL5170) was studied by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Substantial information about the SL5170 chemical composition and curing mechanism was determined through FTIR analysis. The polymerization rate and the maximum degree of reaction were determined directly from experimental DSC curves. Kinetic characterization of epoxy photopolymerization was carried out as a function of the temperature and irradiation intensity and experimental results were compared with an original mathematical model. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3484–3491, 2004     

氨基硅烷活化绢云母改性环氧树脂的固化反应动力学研究

采用氨基硅烷偶联剂(KH550)活化绢云母,在甲基四氢邻苯二甲酸酐(MeTHPA)作用下制备活化绢云母改性环氧树脂.设定不同的升温速率,分别对活化绢云母/环氧树脂/MeTHPA体系进行DSC测定,并采用Kissinger法和Ozawa法处理数据,研究了其固化反应动力学.结果表明,添加活化绢云母前后环氧树脂/MeTHPA...