Adhesives and coatings based on phenolic/epoxy resins

Low molecular weight epoxy resin based on bis (4‐hydroxy phenyl) 1,1 cyclohexane was prepared and modified with various types of the prepared phenolic resins. Phenol–, cresol–, resorcinol–and salicylic acid–formaldehyde resins were used. The optimum conditions of formulation and curing process were studied to obtain modified wood adhesives characterized by high tensile shear strength values. This study indicated that the more suitable conditions are 1:2 weight ratio of phenol–or cresol–formaldehyde to epoxy resin in the presence of phthalic anhydride (20 wt%) of the resin content as a curing agent at 150°C for 80 min. Resorcinol–or salicylic acid–formaldehyde/epoxy resins formulated at 1:2 weight ratio were cured in the presence of paraformaldehyde (20 wt%) at 150°C for 60 min. The effect of the structure of phenolic resins on the tensile shear strength values of formulated resin samples, when mixed with the epoxy resins and cured under the previously mentioned optimum conditions for different times, was investigated. Metallic and glass coatings from the previous resins were also prepared and evaluated as varnishes or paints. Copyright © 1999 John Wiley & Sons, Ltd.     

Novel toughened cyanate ester resin with good dielectric properties and thermal stability by copolymerizing with hyperbranched polysiloxane and epoxy resin

A novel toughened cyanate ester (CE) resin with good dielectric properties and thermal stability was developed by copolymerizing 2,2′‐bis(4‐cyanatophenyl)iso‐propylidene (BCE) with a combined modifier (HBPSiEP) made up of hyperbranched polysiloxane (HBPSi) and epoxy (EP) resin. HBPSi was synthesized through the hydrolysis of 3‐(trimethoxysilyl)propyl methacrylate. The effect of differing stoichiometries of HBPSiEP on the curing characteristics and performance of BCE resin is discussed. Results show that the incorporation of HBPSiEP can not only effectively promote the curing reaction of BCE, but can also significantly improve the toughness of the cured BCE resin. In addition, the toughening effect of HBPSiEP is greater than single EP resin. For example, the impact strength of modified BCE resin with 30 wt% of HBPSiEP is 23.3 KJ/m², which is more than 2.5 times of that of pure BCE resin, while the maximum impact strength of EP/BCE resin is about 2 times of pure BCE resin. It is worthy to note that HBPSiEP/BCE resins also exhibit improved thermal stability, dielectric properties, and flame retardancy, suggesting that the novel toughened CE resins have great potentiality to be used as a matrix for advanced functional composites or electronic packing resins. Copyright © 2009 John Wiley & Sons, Ltd.     

Epoxy-modified, unsaturated polyester hybrid networks

Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin. The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin. Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to other epoxy resins.     

Poly(vinyl chloride) composite emulsion resins modified by polyurethane

An ionomer-type of polyurethane (PU) emulsion was prepared from toluene diisocyanate (TDI), polypropylene glycol (PPG) and dimethylol propionic acid (DMPA) following a self-emulsification process. The modified poly(vinyl chloride) (PVC) emulsion resin was obtained by in situ emulsion copolymerization using the PU as seeds in an autoclave. The effects of PU molecular weight on the mechanical properties and thermal stability of the PU/PVC materials were investigated. The composite latex particles and composite materials were determined and characterized using a laser particle size analyzer, transmission electron microscopy or scanning electron microscopy. The study results showed that the PU/PVC hybrid emulsion particles possess a core/shell structure. When the general mechanical properties of the composite materials increase, the thermal stabilities decrease a little. The tough fractures on the surface of the PU/PVC composite sample following impact are quite obvious. __________ Translated from Journal of Hebei Normal University (Natural Science Edition), 2007, 31(2): 228–232 [译自: 河北师范大学学报(自然科学版)]     

Preparation of nanometer MgO by sol-gel auto-combustion

Nanometer MgO was prepared via a sol-gel auto-combustion technique using magnesium nitrate as raw material and citric acid as chelating agent. IR spectra of the dried gel were used to investigate the structure of the precursors. By studying the different TG curves of magnesium citrate gel prepared by different methods, we found that a combustion process occurred and the nitrate ions acted as an oxidant in the combustion process. TEM photographs of synthesized powders from the sol-gel auto-combustion showed that the crystallites were uniform in size. In addition, the XRD pattern of this sample showed that the particle size was 8.9 nm. The BET curves, in turn, showed that the specific surface of the sample was 26.34 m²/g. The mechanism of the frothing process in restraining agglomeration is discussed. __________ Translated from Journal of East China Normal University (Natural Science), 2007, (2): 52–57 [译自: 华东师范大学学报(自然科学版)]     

Fracture mechanisms in rigid core-shell particle modified high performance epoxies

The fracture mechanisms of a high performance epoxy system modified with two types of preformed rigid core-shell particles (RCSP) were investigated. The use of the preformed RCSP anables the control of the dispersion of the toughener phase in the epoxy, which, in turn, allows the mechanical properties of the modified epoxy to be optimized. The toughening effect via the RCSP modification is found to be as good as that via the core-shell rubber modification. The moduli andT _g of these RCSP-modified epoxies are virtually unaltered via the RCSP modification, when compared with the neat epoxy resin equivalent. The toughening mechanisms in these toughened systems appear to be predominantly crack deflection, crack bifurcation, and microcracking. Approaches for effective toughening of high performance polymers via rigid polymers are discussed.     

双酚A在环氧树脂和端羧丁腈增韧的环氧树脂中作用的研究

本文分别以六氢吡啶、三乙醇胺、70~#酸酐和三氟化硼单乙胺络合物为固化剂,研究了用双酚A改性的环氧树脂和端羧丁腈(简称CTBN)增韧的环氧树脂体系的热、机械性能、微观形貌和交联密度。研究结果表明只有在碱性催化型固化剂六氢吡啶或三乙醇胺下,双酚A的加入才会有突出的增韧效果。结果指出固化物冲击韧性的提高与网络交联密度有关,断裂韧性的提高是析出橡胶相体积分数增大和基体交联密度减小的协同作用所致。     

Mechanical and morphological investigations of reactive polysulfone toughened epoxy networks

The diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was toughened by aminophenyl functional reactive polyethersulfones (R-PES) or by t-butyl terminated non-reactive polyethersulfones (T-PES). The molecular weights of PES were controlled to afford 5,000 to 20,000 g/mole and loadings were also varied from 5 to 30 wt.%. Epoxy networks cured with 4, 4'-diaminodiphenylsulfone (DDS) were subjected to Tg determinations, plane strain fracture toughness (K_1C) measurements, chemical resistance tests and morphological studies by SEM. Very significantly improved K_1C fracture toughness was obtained with reactive PES toughening without loss of chemical resistance, while non-reactive PES blended epoxy resins exhibited only slightly improved fracture toughness but poor chemical resistance. It was possible to load up to 30 wt.% of PES without utilizing solvent and the maximum K_1C fracture toughness with R-PES was around 2.2 MPa-m 0.5, which was equivalent to the neat thermoplastic resin. Ductile fracture of the PES phase is suggested as a major toughening mechanism and this is highly dependent of the excellent adhesion developed between the PES and epoxy phases due to the chemical bonds. The systems demonstrated that chemical resistance of thermosets can be combined with the tough characteristics of thermoplastics.     

端噁唑啉聚醚对环氧树脂的固化与增韧作用的研究

用IR、DSC等分析方法研究了端2-噁唑啉聚环氧丙烷(活性聚醚)与环氧树脂的固化反应,对固化机理作了讨论。并考察了不同分子量活性聚醚对环氧树脂的增韧作用。结果表明,此活性聚醚对环氧树脂增韧效果明显,固化树脂综合性能较好。     

Studies on thermal, mechanical and morphological behaviour of caprolactam blocked methylenediphenyl diisocyanate toughened bismaleimide modified epoxy matrices

Diglycidyl ether of bisphenol A epoxy resin (DGEBA, LY 556) was toughened with 5%, 10% and 15% (by wt) of caprolactam blocked methylenediphenyl diisocyanate (CMDI) using 4,4′-diaminodiphenylmethane (DDM) as curing agent. The toughened epoxy resin was further modified with chemical modifier N,N′-bismaleimido-4,4′-diphenylmethane (BMI). Caprolactam blocked methylenediphenyl diisocyanate was synthesized by the reaction of caprolactam with methylenediphenyl diisocyanate in presence of carbon tetrachloride under nitrogen atmosphere. Thermal properties of the developed matrices were characterized by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), heat distortion temperature (HDT) and dynamic mechanical analysis (DMA). Mechanical properties like tensile strength, flexural strength and impact strength were tested as per ASTM standards. The glass transition temperature (T_g) and thermal stability were decreased with increase in the percentage incorporation of CMDI. The thermomechanical properties of caprolactam blocked methylenediphenyl diisocyanate toughened epoxy resin were increased by increasing the percentage incorporation of bismaleimide. The values of impact strength for epoxy resin were increased with increase in the percentage concentration of CMDI. The homogeneous morphology of CMDI toughened epoxy resin and bismaleimide modified CMDI toughened epoxy resin system were ascertained from scanning electron microscope (SEM).     

Preparation of mesoporous aluminophosphate using poly(amido amine) as template

Mesoporous aluminophosphate was prepared by using G4.0 poly(amido amine)dendrimer as a template and characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ adsorption/desorption methods. Results show that the title compound exhibits a typical mesoporous structure with the average pore size from 5 to 8 nm. The formation mechanism of the nanoporous structure using dendrimer as a template was also discussed. __________ Translated from Journal of Fujian Normal University (Natural Science Edition), 2007, 23(2): 67–70 [译自: 福建师范大学学报 (自然科学版)]     

Preparation of porcine hemoglobin microcapsules of chitosan-sodium alginate

Using an emulsification-gelation method, chitosan-sodium alginate-porcine hemoglobin microcapsules were prepared. Results show that these microcapsules have better forms and small granules with 1 μm size of the mean particle size. They possess a relatively narrow and normal Gaussian distribution. The loading efficiency of porcine hemoglobin (pHb) in microcapsules is more than 90%. The pHb released from microcapsules is extended for more than one month. Chitosan-sodium alginate-hemoglobin microcapsules are expected to become an artificial oxygen-carrying therapeutic agent with sustained release for intravenous injection. Translated from Journal of Hainan University (Natural Science) 2006, 24(3): 239–242 [译自 海南大学学报 (自然科学版)]     

Preparation and properties of polyvinyl acetal sponge modified by chitosan

The polyvinyl acetal sponge modified by chitosan was prepared by adding chitosan/polyvinyl alcohol (PVA) solution during the acetalation reaction of PVA and formaldehyde. The effect of vesicant and chitosan to the pore morphology, water absorption ratio, water absorption rate, expansion time and mechanical properties were studied. The polyvinyl acetal sponge modified by chitosan was used as a hemostatic packing material for the injured rabbit nasal tissue. The hemostatic effect and the healing effect of the modified sponge on the nasal mucosa after nasal surgery were studied. The results indicated that the polyvinyl acetal sponge modified by chitosan has an interconnected pore structure and the wall between large pores also has small pores. The chitosan adhered on the inner surface of the pores. The increased content of vesicant led to an increase in pore diameter, in the water absorption ratio and in expansion time. However, there was only a small change in the water absorption rate and a decrease in tensile strength and compression strength were noted. With an increase in chitosan content, the pore diameter and interconnection of the sponge was reduced. Water absorption ratio, expansion time and water absorption rate decreased, but tensile strength and compression strength improved. Observation of the rabbit nasal tissue after surgical operation suggested that polyvinyl acetal sponge modified by chitosan has an anti-inflammatory, hemostatic and anti-adherent characteristic and could promote the healing and functional recovery of rabbit nasal mucosa. __________ Translated from Journal of Jinan University (Natural Science & Medicine Edition), 2007, 28(3): 283–287 [译自: 暨南大学学报(自然科学与医学版)]     

EPOXY RESIN TOUGHENED BY THERMOPLASTICS

Two kinds of tough ductile heatresisting thermoplastic, namely bisphenol A polysulfone (PSF) and polyethersulfone (PES) were used to toughen thermoset epoxy resin. A systematic study on the relationship between the molecular weight and the terminal group of the thermoplastic modifier and the fracture toughness of the modified resin was carried out. The morphology of PSF modified epoxy resin was surveyed. With the same kind of PSF the structure of the epoxy resin and the toughening effect of PSF was also investigated. The fractography of PSF, particle modified epoxy was examined in detail with SEM. The contribution of every possible energy absorption process has been discussed. Crack pinning mechanism seems to be the most important toughening mechanism for tough ductile thermoplastic PSF particle modified epoxy system.     

低聚端羟基聚硅氧烷接枝增韧酚醛树脂的制备及性能

由低聚羟基封端聚硅氧烷（HO-PDM）与甲醛和苯酚的接枝反应制备了增韧改性酚醛树脂,用FT-IR对改性酚醛树脂的结构进行表征,用电子万能试验机测试了改性前后酚醛树脂的力学性能,用热重分析仪测试改性酚醛树脂的热稳定性。 测得改性酚醛树脂的断裂伸长率、冲击强度、抗拉强度分别为2.8%、2.875 kJ/m2和23.2 MPa;树脂失重20%的温度为431.28 ℃,峰值温度为441.8 ℃,800 ℃的残重率为51.02%。     

Thermal,mechanical, and morphological properties of novolac‐type phenolic resin blended with fullerenol polyurethane and linear polyurethane

Fullerenol polyurethane (C₆₀‐PU) and linear polyurethane (linear‐PU) modified phenolic resins were prepared in this study. Phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends show good miscibility as a result of the intermolecular hydrogen bonding existing between phenolic resin and PU modifiers. DSC and thermogravimetric analysis methods were used to study the thermal properties of phenolic resin blended with different types of PUs. The intermolecular hydrogen bonding that existed between phenolic resin and C₆₀‐PU was investigated by Fourier transform infrared spectroscopy. The morphology and mechanical properties of phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends were also investigated. The char yield of the modified phenolic resins decreased with increasing PU modifier content. Significant improvement in the toughness of the modified phenolic resins was observed. The improvements of impact strength were 27.4% for the phenolic resin/linear‐PU system and 54.3% for the phenolic resin/C₆₀‐PU system, respectively, both with 3 phr linear‐PU and C₆₀‐PU content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2436–2443, 2001     

Thermal and mechanical properties of epoxy resin toughened with epoxidized soybean oil

A series of new modified epoxy resin (EP) cured products were prepared from epoxidized soybean oil and commercial epoxy resin, with methyl nadic anhydride as curing agent and 1-methylimidazole as promoting agent. The thermal properties of the resins were characterized by DMA and TG; DSC was used to determine the curing process. Fourier transform infrared spectroscopy was utilized to investigate their molecular structures and scanning electron microscopy was used to observe the micro morphology of their impact fracture surfaces. Tensile and impact testing was employed to characterize the mechanical properties of the cured products. The combination of commercial EP with 20 wt% ESO resulted in a bioresin with the optimum set of properties: 130.5 °C T _g, 396.9 °C T _50 %, 74.89 MPa tensile strength, and 48.86 kJ m^?2 impact resistance.     

Kinetics of thermal decomposition of CeO2 nanocrystalline precursor prepared by precipitation method

The thermal decomposition of CeO₂ nanocrystalline precursor prepared by chemical precipitation method was investigated using thermo-gravimetric/differential scanning calorimetry (TG/DSC) and X-ray powder diffraction (XRD). In particular, the differential thermal analysis curves for the decomposition of CeO₂ nanocrystalline precursor were measured at different heating rates in air by a thermal analyzer (NETZSCH STA 449C, Germany). The kinetic parameters of the thermal decomposition of CeO₂ nanocrystalline precursor were calculated using the Kissinger method and the Coats-Redfern method. Results show that the apparent active energy E of the reaction is 105.51 kJ/mol, the frequency factor lnA is 3.602 and the reaction order n is 2. This thermal decomposition process can be described by the anti-Jander equation and a three-dimensional diffusion mechanism. Tanslated from Journal of Central South University (Science and Technology), 2007, 38(3): 428–432 [译自: 中南大学学报(自然科学版]     

一种液晶环氧增韧环氧树脂的研究

环氧树脂具有优异的机械性能 ,耐高温以及良好的加工工艺性 .被广泛用于机械、航天、船舶等领域 .由于环氧树脂固化后断裂延伸率小 ,脆性大 ,使其应用受到了一定的限制 .为此 ,国内外学者对环氧树脂进行了大量的改性研究工作 .用含有“柔性链段”的固化剂固化环氧 ,在交联网络中引入柔性链段[1] ;在环氧基体中加入橡胶弹性体[2 ] 、热塑性树脂[3 ,4] 、液晶聚合物[5,6] 等分散相或用热固性树脂连续贯穿于环氧树脂网络中形成互穿、半互穿网络结构[7] ,以改善环氧树脂的韧性 .本文采用液晶环氧化合物原位复合增韧环氧树脂 ,考察了液晶环氧对环…     

丁腈羟增韧环氧树脂形态与力学性能

研究了丁腈羟增韧环氧树脂的力学性能和形态结构，丁腈羟的用量、丁腈羟中丙烯腈的含量、固化条件对所形成的微区尺寸都有较大影响，并进一步影响固化物的力学性能。