Epoxy Value Research Articles

Synthesis, characterization, and properties of silicone–epoxy resins

AbstractSilicone–epoxy (SiE) resins were synthesized through the hydrolytic condensation of 2‐(3,4‐epoxycyclohexylethyl) methyldiethoxysilane (EMDS) and the cohydrolytic condensation of EMDS with dimethyldiethoxysilane. Structural characterization was carried out by 1H‐NMR, 29Si‐NMR, and mass spectrometry analysis; the resins were linear oligomers bearing different numbers of pendant epoxy groups, and the average number of repeat SiO units ranged from 6 to 11. Methyhexahydrophthalic anhydride was used to cure the SiE resins to give glassy materials with high optical clarity. The cured SiE resins showed better thermal stability and higher thermal and UV resistances than a commercial light‐emitting diode package material (an epoxy resin named CEL‐2021P). The effect of the epoxy value on the thermal and mechanical properties and the thermal and UV aging performances of the cured SiE resins were investigated. The SiE resins became more flexible with decreasing epoxy value, and the resin with the moderate epoxy value had the highest thermal and UV resistances. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Crystal structure, curing kinetics, and thermal properties of bisphenol fluorene epoxy resin

AbstractDiglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) monomer was successfully synthesized and characterized in detail. The crystal structure of DGEBF was measured by single‐crystal X‐ray diffraction analysis. Curing kinetics of DGEBF with 4,4‐diaminodiphenyl sulfone (DDS), thermal properties, and decomposition kinetics were investigated using nonisothermal differential scanning calorimetry (DSC) according to Kissinger, Ozawa and Crane methods. The glass transition temperature (Tg), thermal properties of cured polymer were estimated by DSC, dynamic mechanical analysis, and thermogravimetric analyses. Epoxy value of DGEBF monomer up to theoretical value leads to higher crosslink density of cured polymers. The cured DGEBF/DDS system exhibited obvious higher Tg and better thermal stability compared to those of DGEBF/diamine systems reported previously. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis and characterization of cast resin based on different saturation epoxidized soybean oil

AbstractAcrylated epoxidized soybean oils (AESOs) with different level of saturation were obtained by the ring opening of different saturation epoxidized soybean oils using acrylic acid as the ring opener. AESO‐based thermosets have been synthesized by free radical polymerization of these AESOs and methyl methacrylate. The thermal properties of these resins were studied by differential scanning calorimetry and thermo‐gravimetric analysis. The results indicated that the thermal stability of these resins depends upon the epoxy value; the glass transition temperature increases with increasing of epoxy value. The tensile and impact strength of the resins were also studied, and indicated that tensile strength increases with increasing epoxy value, whereas impact strength decreases. The resulting thermosets ranged from elastomers to glassy polymers.

New Thermal and Microbial ResistantMetal‐ContainingEpoxy Polymers

A series of metal-containing epoxy polymers have been synthesized by the condensation of epichlorohydrin (1-chloro-2,3-epoxy propane) with Schiff base metal complexes in alkaline medium. Schiff base was initially prepared by the reaction of 2,6 dihydroxy 1-napthaldehyde and o-phenylenediamine in 1 : 2 molar ratio and then with metal acetate. All the synthesized compounds were characterized by elemental, spectral, and thermal analysis. The physicochemical properties, viz., epoxy value, hydroxyl content, and chlorine content [mol/100 g] were measured by standard procedures. The antimicrobial activities of these metal-containing epoxy polymers were carried out by using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods against S. aureus, B. subtilis (Gram-positive bacteria), and E. coli, P. aeruginosa (Gram-negative bacteria). It was found that the ECu(II) showed higher antibacterial activity than other metal-chelated epoxy resin while EMn(II) exhibited reduced antibacterial activity against all bacteria.

Synthesis of Liquid Crystalline Epoxy Resin p-BDEPB and Cure Kinetics with 3-MeTHPA

A liquid crystalline epoxy resin of p-biphenylene di-4-(2,3-epoxypropyloxy)benzoate (p-BDEPB) was synthesized from allyl bromide, 4-hydroxy ethyl benzoate and 4,4-dihydroxybiphenyl. Its structure and liquid crystalline behavior were characterized by DSC, 1H-NMR, FTIR, POM and XRD. The results are shown that this compound is smectic liquid crystalline.The melting point of p-BDEPB is 210 oC and clearing point is over 300 oC, the epoxy value is 0.312 mol/100g. The average curing Ea of p-BDEPB/3-methyl-tetrahydrophthalic anhydride (MeTHPA) system is 97.2kJ/mol. The gel point of cured-system Tgel is 89.0 oC, curing temperature Tcu is 132.5 oC and finishing temperature Tf is 146.5 oC. The curing reaction can be described by the autocatalytic Šesták-Berggren (S-B) equation, the two reaction orders m and n is 0.23 and 0.74, respectively.

SYNTHESIS AND PROPERTIES OF POLYPHENYLSILICONE AND POLYMETHYLPHENYLSILICONE MODIFIED EPOXY RESINS

Silicone modified epoxy resins were prepared by polycondensation of polyphenylmethoxysilicone(PPMS) and polymethylphenylsilicone(PMPS) with E-20 epoxy resin.Oxirane ring and epoxy values were determined by Fourier transform infrared(FTIR) spectroscopy and HCl/acetone method.The data indicated that silicone oligomers were incorporated into epoxy resin with a random polycondensation and without involving the opening of the oxirane ring in the silicone modified epoxy structure.The influences of silicone contents on the heat-resistant properties of cured silicone modified epoxy resin systems were investigated by differential scanning calorimetry(DSC) and thermogravimetic analysis(TGA).The DSC data showed with increasing siloxane content in copolymers the glass transition temperature(T_g) lowered gradually.But when the mass ratio of epoxy resin to PPMS,PMPS was 7∶3,the T_g was 95.8℃ and 88.3℃,higher than those of unmodified epoxy resins systems by 9.0℃ and 1.5℃ respectively.The TGA data indicated that siloxane moiety exerts its thermal stability on the copolymer through dissipation of the heat,thus delaying thermal degradation of the copolymers.when the mass ratio of epoxy resin to PPMS,PMPS was 7∶3,the 50% weight loss temperature of degradation(T_d) was 476.5℃ and 487.8℃,higher than those of unmodified epoxy resins systems by 58.3℃ and 69.5℃ respectively.In contrast to ED-30 cured system,the heat-resistance and toughness of EPMS-30 cured systems improved more obvious,and its film coatings also showed more excellent filming properties.

Performance of CTBN(carboxyl-terminated poly (butadiene-co-acrylonitrile))-EP(diglycidyl ether of bisphenol-A (DGEBA)) prepolymers and CTBN-EP/polyetheramine (PEA) system

CTBN-EP prepolymers were synthesized from CTBN and epoxy resin under the catalysis of HTMAB. FTIR analyses indicate the formation of ester group between the carboxyl group of CTBN and the oxirane group of epoxy resin. The viscosity of modified prepolymer increases with CTBN content increasing, but the epoxy value of the prepolymer decreases greatly. DSC analyses verify that CTBN affects the curing process of CTBN-EP/PEA system. Mechanical testing presents the improved toughness of CTBN-EP/PEA curings for the decrease of tensile strength, flexural strength and compressive strength, and increase of impact strength and elongation-at-break with the CTBN content increasing. SEM micrographs show the rubber phase with many holes in diameter about 0.5-1.5 μm is formed when CTBN content is lower than 10 phr. However, the pattern of SEM graph shows some stalactite-like strips when CTBN content is higher than 15 phr. Furthermore, the SEM image of 25 phr CTBN sample forms a kind of co-continuous structure.

Synthesis of high‐molecular‐weight epoxy resins from modified natural oils and Bisphenol A or BisphenolA‐based epoxy resins

AbstractA method of synthesis of liquid high‐molecular‐weight epoxy resins from modified vegetable oils as natural raw materials is proposed. The possibility of application of epoxidized soybean, rapeseed, linseed, and sunflower oils as well as hydroxylated soybean and rapeseed oils as raw materials in the fusion process was verified. Reactions of: (i) epoxidized oils, used as low‐molecular‐weight epoxy resins, with Bisphenol A, as well as, (ii) Bisphenol A‐based epoxy resin with hydroxylated natural oils, were carried out in the presence of different catalysts (i.e., LiCl, 2‐methylimidazole, triphenylphosphine, and triethanolamine) in the temperature range of 130–160°C (depending on the catalyst type), and under nitrogen for minimization of the oxidative degradation. The epoxy value, color, number/weight‐average molecular weight, and polydispersity of the products obtained were studied in relation to the reaction conditions. Finally, the possibility of curing of the increased‐molecular‐weight epoxy resins, synthesized from the modified natural oils, with 2‐methylimidazole, dicyanodiamide, hexahydrophthalic anhydride, and triethylenetetramine was checked. The results of this research should enable reducing the use of petrochemical raw materials for the syntheses of high‐molecular‐weight epoxy resins. Copyright © 2008 John Wiley & Sons, Ltd.

Preparation of BPA Epoxy Resin/POSS Nanocomposites and Nonisothermal Co-curing Kinetics with MeTHPA

Polyhedral oligomeric silsesquioxanes epoxy resin (GM-POSS) was prepared from 3-glycidyloxypropyl-trimethoxysilane (GTMS) and methyl triethoxysilane (MTES) by hydrolytic condensation. GM-POSS was characterized using liquid chromatography/mass spectrometry (LC/MS). The epoxy value of GM-POSS is 0.23 mol/100 g. The LC/MS analysis indicates that T 8 and T 9 cages are the majority and contain some amount of T 10. The co-cured nanocomposites of BPA epoxy resin with GM-POSS using 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as the curing agent were prepared and the co-curing kinetics was investigated by nonisothermal differential scanning calorimetry (DSC). The relationship between apparent activation energy Ea and the conversion α was obtained by the isoconversional method of Kissinger, and E a is 68–78 k J/mol. The results show that these curing reactions can be described by the Šesták-Berggren (S-B) equation, which includes two parameters, m and n. For different mass ratio of GM-POSS and BPAER, the two reaction orders, m and n, are in the range of 0.25 ∼ 0.42 and 0.52 ∼ 1.28, respectively. The curing kinetics can be described by the equations

The Miscibility of Novel Bisphenol-Propylene Epoxy Resin With Liquid NBR

A novel kind of bisphenol-type epoxy resin with a vinyl side-chain was developed and its miscibility behavior with liquid nitrile-butadiene rubber (NBR) was investigated. The diglycidyl ether of bisphenol propylene (DGEBP) was prepared by the condensation of phenol with acrolein in the presence of an acid catalyst and the subsequent epoxidization with epichlorohydrin (ECH). The structures of the bisphenol and corresponding epoxy resin were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectral analyses and the epoxy value was determined to be 0.34 mol/100 g by titration. The mixture of DGEBP with the liquid NBR containing diglycidyl ether of bisphenol acetone (DGEBA) was prepared and cured with diaminodiphenylmethane (DDM). The miscibility and morphology of the mixture system were studied by dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM), respectively. The cured mixture of DGEBP/NBR/DDM exhibited good miscibility and, therefore, no separation, along with a transparent appearance at rubber contents of 10 wt% and 30 wt%. For cured DGEBP/DGEBA/NBR/DDM systems at 20 wt% rubber content, the dispersed rubber phase and rubber particles were not observed by DMTA or TEM at DGEBP content above 40 wt%. The DMTA plot showed a single peak related to the glass transition temperature (T g) which decreased with increasing DGEBP content. The appearance of the system varied from transparent to opaque and the rubber separated from the epoxy matrix to form two phases when the DGEBP content decreased. The T g values of the rubber- and epoxy-rich phases were strongly dependent on the DGEBP content in the mixed system. The miscibility of epoxy resin with liquid NBR can be altered by varying the ratio of DGEBP to DGEBA.

Permittivity and tan delta characteristics of epoxy nanocomposites in the frequency range of 1 MHz-1 GHz

To achieve a compact and reliable design of electrical equipment for the present day requirements, there is an urgent need for better and smart insulating materials and in this respect, the reported enhancements in dielectric properties obtained for polymer nanocomposites seems to be very encouraging. To further understand the dielectric behavior of polymer nanocomposites, this experimental work reports the trends of dielectric permittivities and tan delta (loss tangent) of epoxy nanocomposites with single nano-fillers of Al2O3 and TiO2at low filler concentrations (0.1%, 0.5%, 1% & 5%) over a frequency range of 1 MHz-1 GHz. Results show that the nanocomposites demonstrate some very different dielectric characteristics when compared to those for polymer microcomposites. Unlike the usual expectations of increasing permittivity with increasing filler concentration in polymer microcomposites, it has been seen that up to a certain nano-filler concentration and depending on the permittivity of the nano-filler, the permittivities of the epoxy nanocomposites are less than that of the unfilled epoxy at all the measured frequencies. This suggests that there is a very strong dependence of the filler concentration and nano-filler permittivity on the final permittivity of the nanocomposites at all these frequencies. But, in the case of tan delta behavior in nanocomposites, significant effects of filler concentrations were not observed with both Al2O3 and TiO2 fillers. Tan delta values in nanocomposites with Al2O3 fillers are found to be marginally lower at all filler concentrations when compared with the value for unfilled epoxy. But, in TiO2Oepoxy nanocomposites, although the variations in tan delta are not significant with respect to unfilled epoxy, some interesting trends are observed with respect to the frequencies of measurement.

New antimicrobial epoxy‐resin‐bearing Schiff‐base metal complexes

AbstractNew epoxy resins, ER1–M(II) and ER2–M(II) (molar ratio of epichlorohydrin), bearing Schiff‐base metal complexes were prepared by the condensation of epichlorohydrin with Schiff‐base metal complexes (L2M, azomethine metal complexes) in 2 : 1 and 1.25 : 1 molar ratios, respectively, in an alkaline medium. The synthesized epoxy resins were characterized by various instrumental techniques, such as analytical, spectral, and thermal analysis. The epoxide equivalent weight (g/equiv) and epoxy value (equiv/100 g) of the synthesized epoxy resins were measured by standard procedures. The results of thermogravimetric analysis ascribed that ER2–M(II) showed better heat‐resistance properties than ER1–M(II) epoxy resin. The glass‐transition temperatures of all of the synthesized polymers were in the range 153–230°C. The antimicrobial activities of these resins were screened against some bacteria and against some yeast with an agar well diffusion method. All of the synthesized resins showed promising antimicrobial activities. Cu(II)‐chelated resin showed wider effective antibacterial and antifungal activities than the other resins because of a higher stability constant. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Experimental Investigation on the Damping Behaviors of Epoxies with Different Epoxy Value

In this article, five different epoxies including a new kind of flexible epoxy having low glass transition temperatures (11 ∼ 28°C) were prepared using polyamine as curing agent. Damping mechanical tests show that compared with other common available epoxies, the flexible epoxy has high loss factor over broad frequency and temperature range. Activation energy corresponding to glass transition process of different epoxies has been calculated from the temperature corresponding to tan δmax values, obtained at different measurement frequencies. The maximum value of loss factor is 0.71 and the Tg varies from 11 to 28°C, indicating the flexible epoxy can be used as damping polymer materials in common temperature or frequency range.

Kinetics of Curing and Thermal Degradation of POSS Epoxy Resin/DDS System

Polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) was prepared from 3-glycidypropyl-trimethoxysilane (GTMS) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSSER was characterized using Fourier-transformed infrared spectroscopy (FTIR), 1H-NMR, and liquid chromagraphy/mass spectrometry (LC/MS). The epoxy value of POSSER is 0.50 mol/100 g. The LC/MS analysis indicated that T10 is the majority and contain some amount of T8, besides, a trace T9 also exists. The curing kinetics of POSSER with 4,4′-diaminodipheny sulfone (DDS) as a curing agent was investigated by means of differential scanning calorimetry (DSC). The curing reaction order n is 0.8841 and the activation energy Ea is 61.06 kJ/mol from dynamic DSC analysis. Thermal stability and kinetics of thermal degradation were also studied by thermal gravimetric analysis (TGA). TGA results indicated that the temperature of POSSE/DDS system 5% weight loss is approximately 377.0°C, which is higher by 12.6°C than that of pure POSSER, and the primary degradation reaction (300–465°C) followed first order kinetics; the activation energy of degradation reaction is 75.81 kJ/mol.

Synthesis of solid epoxy resins base on BPC II and bisphenol A using conventional heating equipment and microwave

AbstractNew solid state epoxy resins based on diglycidyl ether of 1,1‐dichloro‐2,2 bis (4‐hydroxyphenyl), ethylene (BPC) and BPA epoxy resins in the reaction with BPC and BPA were developed. Solid epoxy resins were synthesised by the use of two different heating methods: conventional and microwave reactor. The use of microwave radiation as novel heating medium as an alternative to the conventional methods, which provide a quicker and more effective synthesis. The solid epoxies have high melting points higher than 100°C and the polycondensation degree remains between n = 4–12. Epoxy value stays low and occurs around 0,02–0,1. BPA epoxy resins and diglycidylether of BPC II were compared in terms of reaction speed. It can be seen that the reaction of BPC diglycidylether occurs approximately 20% quicker given the same reaction conditions of temperature, and balance of catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3850–3854, 2006

Synthesis and characterization of oligosalicylaldehyde-based epoxy resins

AbstractThe synthesis of a new epoxy resin of oligosalicylaldehyde by the reaction with epichlorohydrin is reported. New resin’s epoxy value and chlorine content were determined and found to be 25% and 1%, respectively. The characterization of the new resin was instrumented by FTIR, 1H NMR, scanning electron microscopy, and thermal gravimetric analyses. TGA results showed that the cured epoxy resin has a good resistance to thermal decomposition. The mass losses of cured epoxy resin were found to be 5%, 10%, 50% at 175°C, 240°C, and 400°C, respectively. On the curing procedure the resin was cured with polyethylenepolyamine at 25 °C for 8 h and 100°C for 1.5 h. The FTIR spectrum of new epoxy resin gave the peak of oxirane ring at ṽ = 918 cm−1.

Preparation and characterization of polysiloxane‐modified epoxy resin aqueous dispersions and their films

AbstractPolysiloxane‐modified epoxy resin aqueous dispersions were prepared by the reaction of amino‐polysiloxane (APS) with a graft epoxy resin that was synthesized with a diglycidyl ether of bisphenol A type epoxy resin and styrene/acrylic acid. The measurements of the epoxy values and FTIR spectra confirmed that this reaction really took place. The modified aqueous dispersion exhibits high viscosity, small particle size, and nearly the same surface tension as the unmodified one. Therefore, this indicates that the siloxane segments could be encapsulated into graft epoxy resin particles during the water dispersion process. For APS‐modified films, the thermal stability and water resistance are remarkably enhanced. Furthermore, lowering of the hardness and surface tension for these films was also observed and the surface composition was measured by X‐ray photoelectron spectroscopy. The experimental data indicate that the siloxane segments easily migrate onto the surface during the film formation process and finally enrich on the surface of the APS‐modified film. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 880–885, 2005

Novel nitrogen‐containing epoxy resin. I. Synthetic kinetics

AbstractA novel nitrogen‐containing epoxy resin was synthesized by two steps: (1) condensation reaction between xyleneformaldehyde resin and phenol, to obtain thermoplastic xylenephenolformaldehyde (XPF) resin; and (2) addition reaction between XPF resin and triglycidyl isocryanurate (TGIC). The synthetic kinetics of XPF resin were intensively investigated by gel permeation chromatography (GPC). The results showed that XPF resin, with different molecular weights and low content of free phenol, could be obtained by changing the reaction conditions. The kinetics of reaction between XPF resin and TGIC was monitored by GPC and epoxy value titration. The results showed that the percentage conversion of TGIC was >85% within 60 min at 140°C and the epoxy value, about 0.3–0.4 mol/100 g, varied with the reaction conditions. This novel epoxy resin exhibited good stability of storage and could be used as a basic resin for making prepreg and laminate. The structures of XPF and XT resins were characterized by IR and 1H‐NMR spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96:723–731, 2005

Synthesis and characterization of epoxy resins prepared under microwave irradiation

A new microwave-assisted method of synthesis of solid epoxy resins (SER) with desired epoxy-groups content is described. The method is based on the polyaddition of 4,4′-isopropylidenediphenol (BPA) to a lower-molecular-weight epoxy resin [Rutapox 0162, epoxy value (EV) = 0.57 mol/100 g] in the presence of 2-methylimidazole (2-MI), as a catalyst. Analogical syntheses were performed using conventional heating (i.e., electric heating mantle) for the comparison of properties of SER under both conditions. All the microwave reactions were carried out in the multimode microwave reactor Plazmatronika (Poland) with microwave frequency of 2.45 GHz and maximum microwave power of 600 W. The main advantage of the microwave process is twofold reduction of reaction time in comparison to the conventional heating. Values of EV, Mn, Mw, Mw/Mn, and degree of branching of the products obtained were determined. It was found that the molecular weight distribution and degree of branching in resins synthesized under microwave irradiation was comparable with those obtained under conventional heating and was not influenced by the reduction in reaction time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1969–1975, 2004

Microwave assisted synthesis and determination of chain branching in solid epoxy resins using 1H NMR spectrometry

The degree of branching in solid epoxy resins (epoxy value EV=0.11 mol/100 g) prepared under microwave and conventional conditions has been investigated by 1H NMR spectrometry. The applied method involves rapid reaction between trichloroacetyl isocyanate and hydroxyl groups incorporated in the epoxy resin structure. Solid epoxy resins were prepared by polyaddition of Bisphenol A (BPA) to a lower-molecular-weight (L-M) epoxy resin (Rütapox 0162, EV=0.57) in the presence of 2-methylimidazole (2-MI) as a catalyst. All the microwave reactions were performed in the multimode microwave reactor Plazmatronika-Poland with microwave frequency of 2.45 GHz and maximum of microwave power of 600 W. The results show that the degree of branching in resins synthesized under microwave irradiation is comparable with those obtained under conventional heating (i.e. 6–12%) and is not influenced by the reduction of reaction time.