Synthesis of a new diglycidylic Meldrum acid derivative and study of the curing with lanthanide triflates as initiators

A new epoxy resin derived from Meldrum acid (DGMA) was synthesized by a two steps synthetic procedure and structurally characterized by the usual spectroscopic techniques and elemental analysis. Ytterbium and lanthanum triflates were tested as cationic initiators to cure this resin and its mixtures with diglycidylether of bisphenol A (DGEBA) in several proportions. By FTIR‐ATR spectroscopy the evolution of the groups, which participate in the curing was followed. The evolution of the curing and the T_g of the materials were studied by differential scanning calorimetry and the kinetic parameters were calculated applying isoconversional procedures. Ytterbium triflate led to a quicker curing than lanthanum. The thermal stability of the materials obtained was evaluated by thermogravimetry and the higher thermal degradability of the materials containing DGMA was confirmed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3088–3097, 2008     

New poly(ether‐ester) thermosets obtained by cationic curing of DGEBA and 7,7‐dimethyl‐6,8‐dioxaspiro[3.5] nonane‐5,9‐dione with several Lewis acids as initiators

Scandium, ytterbium, and lanthanum triflates and boron trifluoride monoethylamine were used as cationic initiators to cure a mixture 2:1 (mol/mol) of diglycidylether of bisphenol A (DGEBA) and 7,7‐dimethyl‐6,8‐dioxaspiro[3.5]nonane‐5,9‐dione (MCB). The evolution of the epoxy and lactone during curing and the linear ester groups in the final materials were evaluated by Fourier Transform Infrared in the attenuated‐total‐reflection mode. The kinetic parameters of the curing process were calculated from DSC analysis applying isoconversional procedures. The shrinkage on curing and the thermal degradability of the materials on varying the initiator used were evaluated. The expandable character of MCB was confirmed. The materials obtained were more degradable than conventional epoxy resins due to the tertiary ester groups incorporated in the network by copolymerization. © 2008 Wiley Periodicals, Inc J Polym Sci Part A: Polym Chem 46: 1229–1239, 2008     

Reduction of the shrinkage of thermosets by the cationic curing of mixtures of diglycidyl ether of bisphenol A and 6,6‐dimethyl‐(4,8‐dioxaspiro[2.5]octane‐5,7‐dione)

Ytterbium and lanthanum triflates were used as initiators to cure mixtures of diglycidyl ether of bisphenol A and 6,6‐dimethyl‐(4,8‐dioxaspiro[2.5]octane‐5,7‐dione) in several proportions. The evolution of the epoxy and 6,6‐dimethyl‐(4,8‐dioxaspiro[2.5]octane‐5,7‐dione) bands during curing and the linear ester groups in the final materials were evaluated with Fourier transform infrared in the attenuated‐total‐reflection mode. The use of a conventional cationic initiator, boron trifluoride monoethylamine, was also studied to test the advantages of lanthanide triflates. The shrinkage after curing and the thermal degradability of the materials with variations in the comonomer ratio and the initiator were evaluated and related to the chemical structure of the final network. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6869–6879, 2006     

New powder coatings with low curing temperature and enhanced mechanical properties obtained from DGEBA epoxy resins and Meldrum acid using erbium triflate as curing agent

New low curing temperature powder coatings obtained by copolymerization of epoxy resins with Meldrum acid (MA) initiated by erbium (III) trifluoromethanesulfonate have been formulated. Their mechanical and thermomechanical properties have been studied and compared with a commonly used industrial system (o-tolylbiguanide/epoxy resin) and with an already formulated epoxy powder coating homopolymerized by erbium trifluoromethanesulfonate. Systems containing low proportions of MA and initiated by erbium trifluoromethanesulfonate lead to a great reduction of curing conditions (temperature/time). Moreover, the new formulated systems present very good mechanical properties, adhesion, and impact resistance. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2316–2327, 2007     

Curing and Glass Transition of Epoxy Resins from Ester-Carboxylic Acid Derivatives of Mono- and Disaccharides,and Alcoholysis Lignin

Mono- and disaccharides (SAC) such as glucose (Glc), fructose (Frc) and sucrose (Suc), and also alcoholysis lignin (AL) were dissolved in ethylene glycol and each of the obtained mixtures was reacted with succinic anhydride to form a mixture of ester-carboxylic acid derivatives such as SAC-polyacid, SACPA, and AL-polyacid, ALPA. Ethylene glycol-polyacid (EGPA) was also prepared from ethylene glycol. Each of the obtained mixtures of ester carboxylic acid derivatives was reacted with ethylene glycol diglycidyl ether in the presence of a catalytic amount of dimethylbenzylamine to form ester-epoxy resins. The molar ratios of epoxy groups to carboxylic acid groups ([EPOXY]/[ACID] ratios, mol mol⁻¹) was maintained at 1.0. The contents of SACPA and ALPA in the mixtures of SACPA/EGPA, and ALPA/EGPA, respectively, were also varied from 0 to 100 %. The curing reaction of SucPA and ALPA was studied by differential scanning calorimetry (DSC). Activation energy of the curing reaction for the SucPA system was 80.5 kJ/mol. Thermal properties of epoxy resins were studied by DSC. Glass transition temperatures (T_g) decreased with increasing numbers of repeating units in ester chains between cross-linking points, suggesting that ester chain lengths between cross-linking points mainly affect the mobility of ester chains in epoxy resin networks.     

A study of the degradation of ester-modified epoxy resins obtained by cationic copolymerization of DGEBA with γ-lactones initiated by rare earth triflates

The thermal degradation of new thermosetting materials prepared by cationic copolymerization of mixtures with different proportions of diglycidylether of bisphenol A (DGEBA) with γ-valerolactone (γ-VL) or α-methyl-γ-butyrolactone (γ-MBL) initiated by scandium, ytterbium or lanthanum triflate and a complex of boron trifluoride was investigated. To study the thermal degradation thermogravimetry (TGA) was used. The materials are more degradable than conventional epoxy resins due to the presence of ester groups in the polymer chain, which are broken at the beginning of degradation. The degradability increased with the proportion of linear ester groups and the Lewis acidity of the initiator used in the polymerization and when the proportion of lactone in the initial mixture increased. The kinetic parameters of the degradation were calculated from TGA data by applying isoconversional procedures.     

Crosslinking of mixtures of DGEBA with 1,6-dioxaspiro[4.4]nonan-2,7-dione initiated by tertiary amines, Part II: Thermo-mechanical properties and reworkability

The copolymerization of a DGEBA epoxy resin and a bislactone was studied using different anionic initiators. In the previous work, the kinetics of the process was studied and the differences were observed which could affect the thermal and mechanical properties of the materials. In the present work, the thermo-mechanical properties of these materials have been investigated. An important influence of the final curing temperature on the thermal properties of the materials was detected. The addition of bislactone improved the thermal degradation of the materials due to the introduction of ester groups into the network, which in turn allowed partial or complete recovery and reworkability of the coated material via hydrolysis of the thermoset. In addition, the materials exhibited superior flexibility and toughness, in comparison to the pure DGEBA material.     

The degradation of new thermally degradable thermosets obtained by cationic curing of mixtures of DGEBA and 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione)

The thermal degradation of thermosetting materials prepared by cationic copolymerization of mixtures of different proportions of diglycidylether of bisphenol A (DGEBA) with 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione) (MCP) initiated by ytterbium or lanthanum triflate or using a conventional initiator, BF₃·MEA was investigated. To study the thermal degradation, several techniques were used such as thermogravimetry (TGA), infrared spectroscopy (FTIR) and calorimetry (DSC) and the volatiles evolved during degradation were identified by mass spectrometry. The materials prepared possess the characteristics of thermally degradable thermosets, due to the presence of ester groups in the polymer chain, which are broken at the beginning of degradation. The degradability increased when lanthanide triflates were used in the curing, especially the ytterbium salt and when the proportion of MCP in the material increased.     

Study on the chemical modification of epoxy/anhydride thermosets using a hydroxyl terminated hyperbranched polymer

Mixtures of diglycidylether of bisphenol A (DGEBA) resin and commercially available hyperbranched polyester (HBP) Boltorn H30 were cured by anhydride to covalently bond the hydroxyl end groups in HBP with the epoxy resin. The curing mixtures were investigated by Differential Scanning Calorimetry (DSC) to study the curing evolution and to evaluate the kinetic parameters. DSC studies suggested that HBP could increase the curing rate of epoxy/anhydride systems at low conversions, but it produced a decelerative effect in the last stages of the curing. The influence of the HBP content and the proportion of anhydride on the curing conversions were discussed in detail. The addition of a tertiary amine was proved to decrease the curing temperatures. By Fourier Transform Infrared Spectroscopy (FTIR) the reaction of hydroxyl groups during the whole process was confirmed. By the determination of the conversion at the gelation, we could prove that it increased on increasing the proportion of HBP in the reactive mixture. By Thermomechanical Analysis (TMA) we could determine a reduction of the shrinkage after gelation.     

Thermoplastic-modified epoxy resins cured with different functionalities amine mixtures. Kinetics and miscibility study

The kinetics of a poly(methyl methacrylate) (PMMA)-modified epoxy resin cured with different functionalities amine mixtures was analyzed using differential scanning calorimetry (DSC) in both isothermal and dynamic conditions. A delay in the reaction rate was observed which increased with PMMA content. An approach of kinetic features involved in curing was carried out. A linear dependence of preexponential factors of neat systems with modifier content was considered. The approach shows the contribution of other factors including the dilution effect of the functional groups to the observed delay. Fourier transform infrared spectroscopy (FTIR) indicated a noticeable change in the interactions present in neat systems due to the presence of PMMA. On the other hand, a significant influence of the ratio between each amine in the epoxy/amine mixtures on the final physical appearance was observed. At constant curing conditions, materials from completely opaque (phase separated) to transparent (miscible) were obtained with the increase in monoamine content.     

新型耐腐蚀含氟环氧乙烯基酯树脂的合成与性能

以含氟环氧树脂（F-EP）、丙烯酸（AA）和甲基丙烯酸（MAA）为单体,用顺丁烯二酸（MA）进行改性,合成了含氟环氧乙烯基酯树脂（F-EVER）。用傅里叶红外光谱、热重分析、力学性能分析等手段对产物进行表征,研究了树脂的耐腐蚀性能。结果表明：当以N,N-二甲基甲酰胺（DMF）为催化剂,羧基与环氧基摩尔比为0.9,MA与...     

Studies on the Cure Reaction and Relationship between Network Structure/Thermal Properties of Styrene Copolymers Based on Adypic/Sebacic Acid Modified Unsaturated (Epoxy) Polyesters

The studies on the relationship between network structure/thermal properties of styrene copolymers based on adypic/sebacic acid modified unsaturated (epoxy) polyesters cured using different hardeners as well as the course of the cure reaction of polyesters with styrene have been presented. The adypic/sebacic acid modified unsaturated polyesters (UP) prepared from 4-cyclohexene-1,2-dicarboxylic anhydride (THPA), maleic anhydride (MA), adypic acid (AA) or sebacic acid (SA) and ethylene glycol (EG) and their epoxy derivatives: adypic/sebacic acid modified unsaturated epoxy polyesters (UEP) were subjected to the cure process with styrene using diacyl peroxide: benzoyl peroxide (BPO) or the mixture of BPO/suitable acid anhydride: 4-cyclohexene-1,2-dicarboxylic anhydride (THPA) or glutaric anhydride (GA). Thermal properties were evaluated by means of DSC, TG and DMA analyses. It was proved that studied properties were significantly depended on polyester's structure and the type of applied curing system. Generally, higher values of E'_20°C, tgδ_max, E”, ν_e, IDT, T_k for styrene copolymers based on UEP were obtained. It was connected with more cross-linked polymer network structure due to the possible copolymerization reaction of carbon-carbon double bonds of polyester with styrene and additional polyaddition of epoxy to anhydride groups or thermal curing of epoxy groups. The additional connections between polyester's chains led to obtain more stiff and thermal stable polymeric materials. Moreover, the increase of saturated aliphatic acid's chain length in polyester backbone caused the decrease of E'_20°C, tgδ_max, E”, ν_e, IDT, T_k values of styrene copolymers. It suggested that copolymers based on polyesters prepared from acid containing more methylene groups in their structure were characterized by more flexible polymer network due to the “laxity” effect of aliphatic chains.     

混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

Synthesis and thermal properties of epoxy resins from ester-carboxylic acid derivative of alcoholysis lignin

Alcoholysis lignin (AL) was dissolved in ethylene glycol and the obtained mixture was reacted with succinic anhydride to form a mixture of ester-carboxylic acid derivatives (AL-polyacid, ALPA). Ethylene glycol-polyacid (EGPA) was also prepared from ethylene glycol. The obtained mixture of ester carboxylic acid derivatives was treated with ethylene glycol diglycidyl ether in the presence of catalytic amount of dimethylbenzylamine to form ester-epoxy resins. The curing reaction was analyzed by Ozawa's method using differential scanning calorimetry. The activation energy of curing reaction in the initial step was found to be ca. 84 kJ mol⁻¹. The molar ratios of epoxy groups to carboxylic acid groups ([EPOXY]/[AA] ratios) were varied from 0.8 to 1.3. The contents of ALPA in the mixture of ALPA and EGPA were also varied from 0 to 100%. Thermal properties of epoxy resins were studied by DSC and thermogravimetry. Glass transition temperatures of epoxy resins showed a maximum value of −11.5 °C when [EPOXY]/[AA] ratio was 1.1. T_g increased with increasing ALPA contents suggesting that lignin acts as a hard segment in epoxy resin networks. Thermal degradation temperatures of epoxy resins slightly decreased with increasing ALPA contents.     

Network structure and glass transition of epoxy resins cured with active ester

The effect of network structure on the glass transition temperature (T _g) was examined by differential scanning calorimetry, thermomechanical analysis and dynamic thermomechanometry for epoxy resins cured with mixtures of curing agents consisting of an active ester, 1,3,5-triacetoxybenzene (TAB), and a polyfunctional phenol, 1,3,5-trihydroxybenzene (THB). Free hydroxyl groups are formed from THB after curing, whereas acetyl groups are left from TAB. TheT _g value of cured epoxy resins decreased with increasing TAB content in the curing agent, which is attributed to the looser network structure induced by the steric hindrance of acetyl groups from TAB in the curing reaction and also to the weaker intermolecular interaction and the internal plasticization of acetyl groups from TAB.     

Phosphorus-containing thermosets obtained by cationic copolymerisation of glycidyl compounds with a spiroorthoester or γ-butyrolactone

The synthesis of a bis[(1,4,6-trioxaspiro[4.4]nonan-2-yl)-methyloxy] ethane (bisSOE) and its copolymerisation with mixtures of diglycidyl ether of bisphenol A (DGEBA) and different phosphorus-containing glycidyl compounds led to materials with enhanced flame retardancy and low shrinkage on crosslinking. Analogous materials were obtained by reaction of mixtures where the spiroorthoester (SOE) is formed in the reaction medium from γ-butyrolactone and a diglycidyl compound.The incorporation of phosphorus in the networks increases the LOI values and all crosslinked polymers showed a slight shrinkage after curing, much lower than that observed in conventional epoxy resins. The materials from preformed SOE showed lower shrinkage than the analogues from lactone and epoxy groups.     

Effect of substituents on the curing of liquid crystalline epoxy resin

The synthesis of an aromatic ester based liquid crystalline epoxy resin (LCE) with a substituent in the mesogenic central group is described. Chlorine and methyl groups were introduced as substituents. The curing behaviors of three epoxy resins were investigated using diaminodiphenyl ester as the curing agent. The curing rate and heat of curing of LCE were measured with dynamic and isothermal DSC. The chlorine substituent accelerated the curing of LCE, while the methyl substituent decelerated the curing of LCE. The heat of curing of substituted LCE was diminished compared to LCE with no substituent. Glass transition temperature and elastic modulus of LCE decreased with increasing the size of the substituent. Three liquid crystalline epoxy resins based on aromatic ester mesogenic groups formed a liquid crystalline phase after curing, and the liquid crystalline phase was stable up to the decomposition temperature. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 911–917, 1998     

A furan-derived epoxy thermoset with inherent anti-flammability,degradability, and raw material recycling

The production of multifunctional thermosets with flammability, degradability and raw material recycling from epoxy thermosets made from renewable resources is one of the hottest topics in the context of sustainable development. In this work, we fabricated a fully bio-based epoxy thermoset by curing an as-synthesized furan-derived epoxy monomer (HMF-DDDS-EP) with a furan-based hardener (DFA). Owing to its unique structure containing a Schiff base and disulfide bonds, the cured HMF-DDDS-EP/DFA thermoset integrates a high glass transition temperature, high tensile strength, inherent anti-flammability, degradability, and recyclability. Specifically, a glass transition temperature as high as 171 °C, tensile strength of 62.9 MPa, a storage modulus of 2,356 MPa and outstanding anti-flammability (UL-94 V-0 rating and high LOI of 36.0%) were observed for this fully bio-based epoxy thermoset. Additionally, it was capable of degrading under mildly acidic conditions because of the cleavage of the Schiff base into the original aldehyde monomer. This fully bio-based epoxy thermoset can be considered a representative for fostering the synthesis of advanced thermosetting materials derived from renewable resources.     

Influence of fluorinated acids bonding on surface properties of crosslinked epoxy-based polymers

Two series of crosslinked fluorinated epoxy-based materials containing variable fluorine contents (from 0 to 6 wt.% F) were prepared using formulations based on a fluorinated acid (FA), epoxy monomer and a diamine. The epoxy monomer was based on diglycidyl ether of bisphenol A (DGEBA) while the curing agent was propyleneoxide diamine (Jeffamine D-230). The selected FA were: 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanoic acid (FA1), perfluoro-heptanoic acid (FA2), and perfluoro-nonanoic acid (FA3). One of the series synthesized, FA-DGEBA/Jeffamine, is characterized by covalent attachment of the FA to the polymer by an ester bond. The other series, FA-Jeffamine/DGEBA, is characterized by ionic interaction between FA and polymer chains. The influence on thermal and surface properties of the architecture and chain-length of FA, and the nature of the linkage between FA and network precursors, was analyzed and discussed. It was found that both series showed high oleophobicity, but depending on the linkage between the fluorinated acid and the network, it was possible to develop hydrophobic or hydrophilic materials. The fluorine enrichment with the perfluoroalkyl substitutions was proved by XPS. By this technique it was possible also to analyze the concentration of ammonium groups at the surface.     

电子束辐射固化环氧树脂的反应过程分析

对双酚A型环氧树脂的电子束辐射固化反应过程进行了分析.考察了引发剂、稀释剂对树脂体系辐射反应的影响,以环氧丙烷作为模型化合物,研究了环氧丙烷-碘盐体系的电子束辐射反应机理,证实了在电子束辐射下,碘盐分解产生质子酸,引发环氧树脂阳离子开环聚合的反应过程.观测环氧树脂辐射固化区域发现,电子束穿过样品时发生强烈的散射,在辐射方向以及周围一定区域内引发固化反应,固化反应从活性中心开始向体系内部层层扩展,整个固化区域由很多的层状结构组成.