FORMULATING ANHYDRIDE-CURED EPOXY SYSTEMS
distributed by:Request Quote or SamplesTECHNICAL BULLETINDIXIE CHEMICAL10601 Bay Area Blvd.Pasadena, TX 77507Tel: (281) 474-3271Fax: (281) 291-3384E-Mail: info@dixiechemical.comFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSIntroductionDixie Chemical Company makes a range of alicyclic anhydrides whichare highly suitable for curing epoxy resins. These anhydrides include: Tetrahydrophthalic anhydride (THPA)Hexahydrophthalic anhydride (HHPA)Methyltetrahydrophthalic anhydride (MTHPA)Methylhexahydrophthalic anhydride (MHHPA)Nadic methyl anhydride (NMA)Formulated blends of these materialsDetails about each of these are found in specific Product TechnicalBulletins which are available from Dixie Chemical Company.These anhydrides are commonly used to cure epoxy resins in manychallenging applications, including fiber reinforced composites used inhigh performance aerospace and military applications, as well asmechanically demanding applications like filament wound bearings.They also provide excellent electrical properties for use in high voltageapplications, as well as in encapsulating electronic components andcircuits.Properties of a cured epoxy resin depend on the starting epoxy resin, thecuring agent, the accelerator, the ratio of curing agent to resin, thecuring time and curing temperature, and the post-cure times andtemperatures. No one formulation or one set of process conditions willyield a cured resin having optimum values for all properties. Therefore, it isnecessary to determine the desired properties for the intended end usebefore choosing a formulation. In general, greater cross linking of theresin raises the heat distortion temperature (HDT), hardness, and chemicalresistance, but lowers the impact resistance and flexural strength of thecured product. The following sections discuss the factors which influenceperformance.The data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 1 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSEpoxy ResinsAnhydrides are most commonly used to cure bisphenol A epoxy resins,with the general structure:Liquid epoxy resins with “n” values generally between 0.06-0.12 and epoxyequivalent weight of about 178-192 are commonly chosen for theirmoderate viscosity and good processing characteristics.Typicalcommercial examples of such liquid epoxy resins include:Dow Chemical CompanyHuntsman AdvancedMaterials(Araldite )KukdoMomentive SpecialtyChemicalsNanYaReichhold (EPOTUF )SpolchemieD.E.R. 383D.E.R. 330D.E.R. 331D.E.R. 332D.E.R. 317GY-240GY-250GY-260YD-128EPON 826EPON 828NPEL-12837-140CHS-520NPEL-127CHS-530Anhydrides may also be used to cure higher molecular weight solid epoxyresins with higher “n” values and higher epoxy equivalent weight.Anhydrides give excellent high temperature performance, and havebeen formulated with multifunctional resins such as epoxy phenolnovolacs to get high levels of crosslink density and maximumperformance properties at high temperature.These epoxy phenolnovolacs have the generalized structure:The data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 2 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSTypical commercial examples of such epoxy phenol novolac resinsinclude:Dow Chemical CompanyHuntsman Advanced Materials(Araldite )Momentive Specialty ChemicalsD.E.R. 354D.E.N. 439EPN-1179EPN-1183EPON 154EPON 160D.E.N. 431D.E.N. 439EPN-1180GY-289EPON 162Anhydrides give excellent electrical properties when formulated withbisphenol A epoxy resins or epoxy phenol novolacs. This performance hasbeen extended to the cure of cycloaliphatic epoxy resins forencapsulating high performance electronic components, including lightemitting diodes. Examples of these cycloaliphatic epoxies are l) adipateThe data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 3 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSdiglycidyl ester ofhexahydrophthalic aciddiglycidyl ester of tetrahydrophthalic acidCure ChemistryIn curing an epoxy resin, an anhydride group reacts with an aliphatichydroxyl to give an ester group and a free carboxylic acid. This is shownhere using HHPA:The free carboxyl group reacts with an epoxy group in the following wayto give an α-hydroxy ester:Bisphenol A epoxy resins have low levels of aliphatic hydroxyls to initiatecure with anhydrides. Also, every time a carboxylic acid group reactswith an epoxy group, another aliphatic hydroxyl is created, and is thenavailable to react with another anhydride group.The data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 4 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSIn addition, commercial anhydrides have very low levels of residualcarboxylic acid. These acid groups can react with epoxy groups toinitiate cure and to create more aliphatic hydroxyl groups to cure withanhydride groups.It can be seen that the ideal stoichiometry of the anhydride cured epoxyis one mole of anhydride per mole of epoxy.The idealized structure for a bisphenol A epoxy resin cured with ananhydride can be represented as follows, using HHPA as the example:It will be noted that each epoxy molecule is connected to about fouranhydride molecules and each anhydride molecules is connected to twoepoxy molecules. This provides a high crosslink density which gives theexcellent performance of epoxies cured with these alicyclic anhydrides.Side ReactionsThe data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 5 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSAn important side reaction is homopolymerization of the epoxy, as shownin the following mechanism:This reaction consumes epoxy which is otherwise needed to react withacid from the anhydride. It is acid or base catalyzed, so either free acidfrom the anhydride, or base accelerators can promote it. It is a significantside reaction for either under-catalyzed systems or for systems that areover-catalyzed with strong base accelerators. So when evaluating arange of accelerator levels, one typically finds an optimum acceleratorlevel for particular physical performance properties like glass transitiontemperature, heat distortion temperature, tensile modulus, etc.Cure AcceleratorsIn curing an epoxy with an anhydride, cure accelerators are generallyused to speed the cure process and to achieve desired performancecharacteristics. Various materials may be used to catalyze the reactionbetween anhydrides and epoxies.Tertiary amines are effectiveaccelerators.Commonly used examples are benzyldimethylamine(BDMA), dimethylaminomethylphenol, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30 from Dow Chemical or Ancamine K-54 from Air Products),and 1,4-diaza bicyclo[2.2.2]octane, and 1,8-diazabicyclo[5.4.0]undec-7ene.Liquid imidazoles are also frequently used to catalyze anhydride-epoxyreactions. Commonly used imidazoles include 2-ethyl-4-methyl imidazole,1-methyl imidazole, 1-benzyl-2-methyl imidazole, etc.Tertiary amines and imidazoles generally give significant amber or browncolor to cured systems.Quaternary ammonium salts, like benzyltriethylamonium chloride (BTEAC),benzyltrimethyl ammonium chloride (BTMAC), or tetrabutyl ammoniumbromide (TBABr) can be used, but since they are solid salts, they must beThe data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 6 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSdissolved in a suitable liquid like ethylene glycol or methanol so that theycan be adequately mixed into a liquid anhydride.Quaternaryammonium salts have the advantage that they promote lower colorcures.Dixie Chemical Company makes a liquid blend of 60% BTEAC and 40%ethylene glycol.Named AP-6G, this liquid can be easily andconveniently dispersed in liquid epoxy-anhydride blends. AP-6G impartsgood glass transition temperature (Tg) and extended pot life toanhydride/epoxy formulations, and allows the production of relatively lowcolor polymers.Organometallic salts based on tin, zinc, or chromium can also be used.The chromium salts are generally green and give a significant green colorto the epoxy-anhydride matrix. Tin and zinc salts can give relativelycolorless cures.Preparing the Curing Agent/Accelerator MixtureThe sequence of mixing can have a marked effect on the properties ofthe cured epoxy resin. Direct addition of an amine catalyst to theanhydride is not recommended. If the accelerator is added to theanhydride before the resin, a darker color may result. To obtain the bestproperties, the following procedure is recommended:Mixing methoda)b)c)Mix anhydride and epoxy resin.Add the accelerator.Mix until completely uniform.Anhydride LevelThe data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 7 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSThe amount of anhydride in the formulation is generally expressed in partsper hundred parts of epoxy resin (phr). To calculate the amount ofanhydride required, use the following equation:Anhydride, phr (100/EEW)x AEW x A/EWhere:EEW epoxy equivalent weightAEW anhydride equivalent weight.A/E ratio of anhydride equivalent to epoxide equivalent. As notedabove, the ideal stoichiometry is 1:1, but the optimum value for this maybe in the range of 0.90-0.95 to account for side reactions such as the onediscussed above which also consumes epoxy. This is best determined byexperimentation, where formulations are prepared which vary from the1:1 stoichiometry. Key performance characteristics are evaluated foreach formulation to identify the optimum A/E ratio for the performanceproperties of interest.Cure CycleCuring an epoxy resin may be carried out in one or more stagesdepending on the rate of reaction and the exotherm of the mixture.Better control can be achieved by curing at a lower temperature. A slowinitial cure followed by a post-cure at a higher temperature usually yieldsthe best results. Using this approach allows the reaction to proceed moreslowly and the associated exothem to be lower. This results in better colorand fewer stresses in the cured epoxy resin.The post-cure anneals the resin thus relieving any stresses which may bepresent after the initial cure.The cure cycle used has a dramatic effect on system performance. Thiscure cycle includes the initial time and temperature used to cure theformulation, as well as all post-cure times and temperatures used toimprove performance properties. This is important because longer curetimes and higher cure temperatures promote increases in crosslinking.Higher crosslinking results in higher levels of mechanical strength andchemical resistance.The data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 8 of 9
distributed by:Request Quote or SamplesTECHNICAL BULLETINFORMULATING ANHYDRIDE-CURED EPOXY SYSTEMSA typical cure cycle for curing liquid epoxy resins is 2 hours at 90 C, plus 4hours at 165 C, plus up to 16 hours at 200 C.Handling PrecautionsRead and understand the relevant Material Safety Data Sheets (MSDS) forall products before use. These anhydrides are primary skin and eyeirritants. Avoid contact with skin, eyes, and clothing. Use only withadequate ventilation. In case of contact, follow the procedures outlinedin the MSDS. Generally, these procedures include immediately flushingthe affected skin or eyes with copious amounts of water for at least 15minutes. In the case of eye contact, get medical attention. Washcontaminated clothing before reuse.Follow the recommendations in the MSDS for personal protectiveequipment when handling these materials.At a minimum, theseprocedures typically include protective chemical goggles, impenetrablegloves, and measures to avoid breathing chemical vapors.The data contained herein are furnished for information only and are believed to be reliable. This information is provided only as guidance and is not to beconsidered a warranty or quality specification. Dixie Chemical Company, Inc. makes no warranties (expressed or implied) as to its accuracy and assumes noliability in connection with any use of this product.Page 9 of 9
10601 Bay Area Blvd. FORMULATING ANHYDRIDE-CURED EPOXY SYSTEMS Introduction Dixie Chemical Company makes a range of alicyclic anhydrides which . circuits. Properties of a cured epoxy resin depend on the starting epoxy
dioxide) is an acid anhydride derived from a carbonic acid (H 2 CO 3). Some other examples are given below. Organic acid anhydrides o Acetic anhydride (the simplest organic acid anhydride) o Maleic anhydride o ATP in its protonated form o Acetic, formic anhydride Inorganic acid anhydrides
Contents 3 Epoxy resins, water-reducible 4 Epoxy hardeners, water-reducible 5 Epoxy resins solid and solutions 6 Epoxy resins liquid and reactive diluted 7 Reactive diluents for epoxy resins 7 Epoxy hardeners, polyamines 8 Epoxy hardeners, adducts 9 Epoxy hardeners, mannich bases 10 Epoxy hardeners, polyamidoamines 11 Survey of the qu
Tile-Clad HS Epoxy : Water-Based Tile-Clad Pro Industrial High Performance Epoxy : Epolon II Multi-Mil Epoxy Macropoxy HS Epoxy : Macropoxy 646 Fast Cure Epoxy High Solids Catalyzed Epoxy : Macropoxy 846 Winter Grade Epoxy Sher
mechanical properties of epoxy resins, physical and chemical properties of epoxy resins, epoxy resin adhesives, epoxy resin coatings, epoxy coating give into water, electrical and electronic applications, analysis of epoxides and epoxy resins and the toxicology of epoxy resins. It will be a standard reference book for professionals and .
[22] 58 finger no Cx yes Fluc 2 weeks cured Pigeon keeper [22] 14 leg yes Cx no None cured [22] 37 hand yes Cx yes Keto 1.5 months cured [22] 44 hand yes Cx yes Fluc 3 weeks cured [22] 39 eyelid no Cx no Itra 2 months regression [22] 78 finger yes Cx yes Fluc 2 weeks cured [23] 53 buttock no Cx yes Ampho B/5-FC 6 weeks cured Pigeon exposure
Curing, Gelling, Thermomechanical and Thermal Decomposition Behaviors of Anhydride-Cured Epoxy (DGEBA)/Epoxidized Soybean Oil (ESO) Compositions . and epoxidized linseed oil (ELO), added them up to 50 wt.%, and cured the corresponding formulations with anhydride. Unlike to the EP/ELO blends, the EP with 30 wt.% ESO showed a two-phase .
formic anhydride O OO acetic anhydride ethanoic anhydride O OO Cl acetic 4-chlorobenzoic anhydride Carboxylic Acids and Derivatives Nomenclature Esters Systematic names for esters are derived by first giving the name of the alkyl group attached to the oxygen, and then ide
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