New hyperbranched polyether containing cyclic carbonate groups as a toughening agent for epoxy resin

Hyperbranched polyglycerol containing terminal five-membered cyclic carbonate groups has been obtained by anionic polymerization of glycidol and then in the reaction of its terminal vicinal hydroxyl groups with dimethyl carbonate in the presence of potassium carbonate. The remaining OH groups of the polymer were protected in the reaction with acetic anhydride to reduce polymer hydrophilicity and increase miscibility with the epoxy resin. A strong decrease in viscosity was observed after esterification, from 73 to 3.6 Pa s. The product (HBPG 3) was used for modification of the bisphenol A based epoxy resin. The epoxide-cyclic carbonate compositions were cured using a polyamine hardener (TETA) in a one-step procedure. Thermal and mechanical properties of the cured compositions were characterized and compared with the parent epoxy resin. The optimal mechanical properties were obtained for the compositions containing HBPG 3 when phase separation takes place. The mechanical properties are discussed in terms of the morphology observed by SEM.     

Autocatalytic curing kinetics of thermosetting polymers: A new model based on temperature dependent reaction orders

Herewith we discuss a new model for thermoset polymers that follow the autocatalytic curing kinetics. This model is proposed upon investigation of the crosslinking reaction of 2,2′-Bis(4-cyanatophenyl)iso-propylidene (BACy), under isothermal conditions over a range of temperatures between 180 °C and 260 °C without catalyst. BACy undergoes crossslinking via a trimerization mechanism of the nitrile groups following an autocatalytic kinetics rather than an nth order kinetics. Comparing with other autocatalytic kinetics models, the new model takes into account that the reaction orders of the curing reactions in the polymers are temperature dependent variables rather than constants. The new model provides excellent agreement with the experimental data in a wide range of conversions and reaction temperatures.     

Evaluation of bisacrylate terminated epoxy resins as coatings

The paper describes the effect of backbone flexibility on the coating performance of vinyl ester resin. For this purpose four resins of varying flexibility were prepared. Bisacrylate terminated epoxy resin (D) was prepared by reacting 2 mol of acrylic acid with 1 mol of diglycidyl ester of hexahydrophthalic anhydride. The flexibility of the backbone was increased by chain extension of mono acryloxy derivative of diglycidyl ester of hexahydrophthalic anhydride with sebacic acid (resin G′). Partial cross-linking of resin D containing pendant hydroxyl group was also done by reacting with small amounts of isophorone diisocyanate (D₂I₁₀, D₂I₄).     

Processing of intractable polymers using reactive solvents. 6. A new reactive solvent concept based on reversible depolymerisation

The use of reactive solvents which reversibly (de)polymerise to facilitate the processing of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was explored. PPE can be dissolved at elevated temperatures in very low molecular weight thermoplastic poly(urethane) (TPU) fragments obtained via depolymerisation and these solutions can then be processed at the relatively low temperature of 250 °C. After processing and upon cooling, the TPU fragments repolymerise which induces a L-L phase separation between PPE and TPU followed by vitrification of the PPE matrix phase and at lower temperatures vitrification of the TPU dispersed phase. Since phase separation occurs during cooling, the phase separation is induced thermally as well as chemically, since the molecular weight of the ‘solvent’ increases upon lowering the temperature. The properties of the final materials, such as heat resistance, are dominated by the continuous PPE matrix. The starting molecular weight of TPU and the composition of the blend had pronounced effects on the phase separation, morphology and viscosity of the blends. Increasing the amount of TPU resulted in larger TPU particles but no effect on the T_g of the PPE-rich matrix was observed. Increasing the starting molecular weight of TPU resulted in higher phase separation temperatures and higher T_gs for the PPE-rich matrix. Possibilities for diminishing the residual TPU fractions were explored. The interference of vitrification with phase separation could be postponed and, consequently, the residual fraction of TPU in the PPE phase could be reduced either via an increase in the starting molecular weight of TPU or a decrease in cooling rate or T_g of the matrix.     

Time-temperature and time-irradiation intensity superposition for photopolymerization of an epoxy based resin

In this paper the photoinitiated polymerization of a commercially available epoxy based resin for stereolithography (SL5170) was studied by means of photo differential scanning calorimetry (pDSC) at different temperature and irradiation intensities. Experimental results showed that temperature and light intensity have the same qualitative effects on the reaction kinetics. Time-temperature and time-intensity superposition principle was applied to the experimental curves. In both cases, it was shown that curves shifting on the time axis determines a single master curve. Individual curves significantly diverge from the master curve for high conversions, indicating that different regimes are encountered during photocuring of commercial stereolithography cationic resin. For low conversions, the reaction is kinetically controlled, whereas it becomes mainly diffusion controlled when the glass transition temperature approaches the isothermal cure temperature. At high conversion, master curves were also built in the diffusion-controlled regime, using different shift factors. The applicability of master curves to photopolymerization of epoxy based resin for stereolithography indicates that the mechanisms involved in network formation in the kinetic controlled regime are the same regardless of temperature and irradiation intensity. Consequently, time temperature transformation (TTT) and time intensity transformation (TIT) curves were built, as the time needed to reach polymer vitrification at each temperature and irradiation intensity.     

The effect of the morphology on the hygroelastic behaviour of polyester and epoxy resins

The effect of the morphology on the hygroelastic behaviour of polyester and epoxy resins is studied. The morphology is expressed by two factors, namely, the free volume of the polymer and a two-phase formation. The first factor is varied in styrene-crosslinked polyester using different styrene/alkyd proportions, and by using different immersion temperatures. The second is investigated in polyesters by replacing styrene with bromostyrene inducing a two-phase structure, and in epoxies by changing the hardener/epoxy ratio. It is shown that the hygroelastic response is affected markedly by the morphology. In general, both the moisture content and its rate of absorption are higher when the polymer network is more open and when more free volume is available. In some cases, however, the hygroelastic parameters are dominated by a two-phase structure where present.     

Synthesis and application of a novel epoxy grafted thermosetting acrylic resin

A novel manufacturing process for high performance metallic can coating was carried out based on an epoxy‐grafted acrylic resin. Firstly, the epoxy resin was reacted with acrylic amide forming a ring opened product epoxy‐amide resin, and then the product obtained copolymerized with all other monomers, such as acrylic acid (AA), butyl acrylate (BA), hydroxypropyl acrylate (HPA), 2‐ethylhexyl acrylate (2‐EHA), methyl methacrylate (MMA), styrene (St), using free radical solvent polymerization in the presence of BPO. The resins prepared present the transparent appearance, and the target resin coating based on these resins exhibits excellent boiling resistance and chemicals resistance and can be applied as the protective coating for metallic can. The effects on the coating properties, such as amount of acrylic acid, 2‐EHA wt % between 2‐EHA and BA, amount of amino resin, amount of catalyst, and so forth, were investigated. In addition, the influences of polymerization time on the conversion ratio of monomers were also studied. Results show that under the optimal conditions, the target resin coating provides excellent physical and mechanical properties. The various properties tests for this coating have been performed in accordance with the standards of ASTM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies of the properties of a thermosetting epoxy modified with block copolymers

Poly[(n‐butyl acrylate)‐block‐poly(methyl methacrylate)‐co‐(glycidyl methacrylate)] (BMG) diblock copolymers incorporating an epoxy‐reactive functionality in one block have been synthesized and used as modifiers for the model epoxy resin E‐51 cured with 4,4′‐diaminodiphenyl methane (DDM). The properties and morphologies of the modified epoxy thermosets were investigated by dynamic mechanical analysis (DMA), impact testing and scanning electron microscopy (SEM). The results reveal that addition of the block copolymers leaves the glass transition temperatures of the blends relatively unchanged, with small decreases in the storage moduli at room temperature. The toughening effect is dependent on the chemical structures of the block copolymers and an increase in the impact strength by a factor of two was obtained by the addition of ‘relatively symmetrical’ block copolymers. Moreover, the impact test results are consistent with the morphologies of the fracture surfaces as evidenced by SEM. Copyright © 2005 Society of Chemical Industry     

Crown ethers as new curing agents for epoxy resins

Different crown ethers (4‐aminobenzo‐15‐crown‐5 (4‐aminobenzo‐15‐C5), 1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane (diaza‐18‐crown‐6), tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (H₄DOTA) and tetraazacyclododecane‐1,4,7,10‐tetraacetamide (H₂ODDA)) were used as curing agent for bisphenol A diglycidyl ether (BADGE, n = 0). The maximum enthalpy change for all systems except that formed by the epoxy resin with H₄DOTA corresponds to a stoichiometric ratio, since from this value the reaction enthalpies decrease when the proportion of epoxy increases. Heteropolymerization reaction occurs in all the crown ethers. Etherification reactions occur at temperatures much lower (30 °C less) than for the porphyrin systems studied in which a second signal appears at 300 °C. The etherification is evidenced by a slight shoulder in the thermograms for H₄DOTA and H₂ODDA. The systems BADGE (n = 0)/4‐aminobenzo‐15‐C5 and BADGE (n = 0)/diaza‐18‐crown‐6 improve the thermal stability of the epoxy resin by 30 °C approximately while the improvement for BADGE (n = 0)/H₄DOTA and BADGE (n = 0)/H₂ODDA is about 60 °C. © 2017 Society of Chemical Industry     

Changes of solubility parameters during evaporation of solvents as a factor influencing the self-stratification of epoxy/acrylic systems

Behaviour of solutions of binary mixture of epoxy/acrylic resins during solvent evaporation was examined. Properties of various liquid compositions at different stages of solvent evaporation were characterised by their solubility parameters and surface tension. Both parameters were calculated from the weight fractions of particular components determined by gas chromatography (GC). Phase separation during solvent evaporation and self-stratification were observed and characterized using optical microscopy and FTIR methods. The results of investigations indicate the possibility of using these methods in order to foresee behaviour of binary compositions.     

Silane functionalization of perfluoroether oligomers for reaction management and morphology control of two‐phase epoxy networks

Mixtures of an epoxy resin, hardener, and acid functionalized perfluoroether oligomers will readily undergo phase separation during curing. However, the conditions to bring about the growth of nuclei into microscopic particles have hitherto been found only for systems cured with anhydrides. In the present study perfluoroether oligomers were functionalized by established procedures to introduce both carboxylic acid groups and alkoxysilane groups in sites within the chain extended segments. The presence of alkoxysilane groups together with the prereaction step with an excess epoxy resin, prior to the addition of the aromatic amine hardener, induced phase separation by a nucleation‐and‐growth mechanism. The dual functionality in the perfluoroether oligomer was even more beneficial when the alkoxysilane groups were hydrolyzed prior to the addition of the amine hardener. Under such circumstances the precipitation of the perfluoroether oligomer occurred quantitatively, as indicated by the complete absence of any plasticization effects in the epoxy matrix. From electron microscopy examinations, thermal analysis, and measurements of mechanical properties it was possible to deduce a plausible mechanism for the formation of the typical core‐shell aggregates within the precipitated particles for these systems, which could also be applied to other systems, such as those using carboxylic‐acid‐terminated butadiene acrylonitrile oligomers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1036–1049, 2005     

环氧树脂固化剂的改性研究

以异佛尔酮二胺和1,6-己二胺为原料,加入适量自制的催化剂,在190℃反应2.5 h,即制成新型环氧树脂固化剂(简称YFJA)。将其按不同比例添加到传统固化剂二氨基二苯甲烷(简称DDM)和甲基四氢苯酐(简称Me-THPA)中,通过对固化物的冲击强度、拉伸强度和力学损耗等性能的检测分析,发现当自制固化剂添加量为固化剂总量的50%时,体系的力学性能达到最佳效果,冲击强度最高可提高346.5%,拉伸强度可提高73.0%。     

Mechanical properties and morphology of epoxidized soyabean‐oil‐modified epoxy resin

Epoxidized soyabean oil (ESO) has been used to toughen epoxy resin cured with an ambient temperature hardener. The ESO was prepolymerized before blending with epoxy resin to obtain modified networks having various concentrations of ESO. The modified networks were also made by blending the ESO with epoxy resin by a one‐stage process. All the modified networks were characterized for their thermal, flexural and impact properties, and compared to the parent epoxy network. The optimum properties were obtained at 20 parts per hundred grams of resin (phr) of ESO. The impact behaviour is explained in terms of morphology observed by scanning electron microscopy. © 2001 Society of Chemical Industry     

Effects of Tween 80 concentration as a surfactant additive on morphology and permeability of flat sheet polyethersulfone (PES) membranes

In this study, effects of Tween 80 (polyoxyethylene sorbitan monooleate) as a variable hydrophilic surfactant additive on morphology and permeability of flat sheet polyethersulfone (PES) membranes prepared from PES/polyethylene glycol (PEG)/n-methyl-2-pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath were investigated. Cross-sectional morphology of the prepared membranes was studied by scanning electron microscopy (SEM). Permeation performance of the prepared membranes was evaluated in terms of pure water permeability (L_P), water content, porosity, hydraulic permeability and thickness of the prepared membranes. It was found out that little addition of Tween 80 to the casting solution increases water content and porosity of the membrane support layer and enhances pure water permeability through the membranes.     

Reactive core/shell type hyperbranched blockcopolyethers as new liquid rubbers for epoxy toughening

Novel reactive core/shell-type hyperbranched blockcopolyethers were tailored as new class of liquid rubbers useful as flexibilizers and toughening agents of anhydride-cured epoxy resins. Anionic ring-opening polymerization of glycidol onto a six-arm star poly(propylene oxide-block-ethylene oxide) afforded hyperbranched polyether cores as macroinitiators for propylene oxide graft copolymerization. The hydroxy end groups of the resulting polyether-polyols have been modified in order to prepare stearate, hydroxy benzoate and epoxy derivatives. The modification afforded reactivity and polarity design which has been the key to improved blend performance with epoxy resins. In comparison to conventional hyperbranched epoxy-terminated polyesters, the influence of molecular architectures on thermal, mechanical and morphological properties of hexahydrophthalic acid anhydride-cured bisphenol-A diglycidylether was examined. As a function of polarity and reactivity design, it was possible to control phase separation and to vary mechanical properties from highly flexible to stiff and tough.     

Cure kinetics and morphology of blends of epoxy resin with poly (ether ether ketone) containing pendant tertiary butyl groups

The cure kinetics and morphology of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin modified with a poly (ether ether ketone) based on tertiary butyl hydroquinone (PEEK-T) cured with diamino diphenyl sulphone (DDS) were investigated using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamic mechanical thermal analysis (DMTA). The results obtained from DSC were applied to autocatalytic and diffusion controlled kinetic models. The reaction mechanism broadly showed autocatalytic behaviour regardless of the presence of PEEK-T. At higher PEEK-T concentration, more diffusion controlled mechanism was observed. The rate of curing reaction decreased with increase in thermoplastic content and also with the lowering of curing temperature. The activation energies of the blends are higher than that of the neat resin. The blends showed a phase separated morphology. The dispersed phase showed a homogeneous particle size distribution. The T_g of the neat resin decreased with the decrease in cure temperature. Two T_g's corresponding to the epoxy rich and thermoplastic rich phases were observed in the dynamic mechanical spectrum. The storage modulus of 10 and 20 phr PEEK-T blends are found to be greater than the neat resin.     

新型环氧树脂增韧剂的合成与研究

以聚醚和酸酐反应，再与环氧树脂反应，合成了一种新型的以环氧基封端的内增韧活性增韧剂，讨论了该增韧剂的固化特性和最佳掺合比例，在100份环氧树脂中加入10份这种增韧剂，环氧树脂固化物综合力学性能较好，剪切强度为23．6MPa，压缩强度达70．2Mpa。     

Multiarm star poly(glycidol)-block-poly(styrene) as modifier of anionically cured diglycidylether of bisphenol A thermosetting coatings

Well-defined multiarm star copolymer poly(glycidol)-b-poly(styrene) (PGOH-b-PS) with an average number of PS arms per molecule of 85 has been prepared. The core first approach has been selected as the methodology using atom transfer radical polymerization (ATRP) of styrene to grow the arms from an activated hyperbranched poly(glycidol) as core. This activated hyperbranched macroinitiator was prepared by esterification of hyperbranched poly(glycidol) (PGOH) with 2-bromoisobutyryl bromide.PGOH-b-PS was used to modify diglycidylether of bisphenol A coatings cured by anionic ring-opening mechanism using 1-methyl imidazole as the initiator. The kinetics of the curing process, studied by dynamic scanning calorimetry (DSC), was not much affected when PGOH-b-PS was added to the formulation. By rheometry the effect of this new polymer topology on the complex viscosity (η^*) of the reactive mixture was analyzed. The phase-separation of the modified coatings was proved by dynamic thermomechanical analysis (DMTA) and electronic microscopy (SEM and TEM) showing nano- or microphase separation as a function of the modifier content. The addition of this star polymer led to increase in the rigidity in terms of Young's modulus and in the microhardness in comparison to neat DGEBA.     

Heavy crude oil asphaltenes as a nanofiller for epoxy resin

Asphaltenes are harmful components of heavy crude oils and require rational utilization after oil refining or deasphalting. Asphaltenes are macromolecules containing various functional groups that self-assemble to nanoscale aggregates and can be used as nanofillers for polymers. In this research, mixtures of asphaltenes with the diglycidyl ether of bisphenol A were considered. The solubility of asphaltenes in this epoxy resin, the rheological properties of the mixtures, and the effect of asphaltenes on the curing with 4,4′-diaminodiphenyl sulfone were studied. In addition, the glass transition temperature, strength, and adhesion characteristics of the asphaltene-filled cured composites were evaluated. The dual role of asphaltenes in polymer modification was demonstrated: the asphaltenes simultaneously plasticize and reinforce the polymer matrix, and the transition from predominant plasticization to strengthening occurs with an asphaltene content at 20 wt%. The dual reinforcement/plasticization effect occurs because epoxy composites contain both nanosized and microsized particles of asphaltenes due to the partial dissolution of asphaltenes in the epoxy resin and the decrease in their solubility during high-temperature curing.     

Synthesis of isocyanurate-based imidazole carboxylate as thermal latent curing accelerator for thermosetting epoxy resins

A novel thermal latent curing accelerator, 1-(2-cyanoethyl)-2-methylimidazole/tris (2-carboxyethyl) isocyanurate adduct (2MICN-T), was successfully synthesized through an acid–base neutralization of tris(2-carboxyethyl)isocyanurate (TCEIC) and 1-(2-cyanoethyl)-2-methylimidazole (2MICN). It was further added into diglycidylether of bisphenol A based epoxy resin/methylhexahydrophthalic anhydride mixture to form one-component curing systems. With the addition of 2 wt% of 2MICN-T, the one-component system could be steadily stored for more than 1 month at room temperature, while the shelf life of 2MICN curing system was only 2 days. Nonisothermal differential scanning calorimeter also demonstrated the excellent thermal latency of 2MICN-T in low-temperature region and rapid initiation of the curing reaction when raising temperature. Compared to the cured resins with original 2MICN as accelerator, the resulted thermosets exhibited enhanced glassy storage modulus, glass transition temperature, and thermal stability when 2 wt% of 2MICN-T was applied. It was attributed to the chemical incorporation of the isocyanurate moieties with multi carboxyl groups and nitrogen-contained heterocyclic ring, effectively increasing the crosslinking density, chain rigidity, and heat resistance of the cured resin. Thus, it is suggested that 2MICN-T can play both roles as latent curing accelerator and modifier for one-component epoxy compounds, and is particularly recommended for application in electronic packaging fields.