Epoxy resins hardening

In order to obtain cured products with higher heat distortion temperatures from bis-phenol epoxy resins, hardeners with higher functionality have been used, thus giving a higher degree of cross-linking. These include pyromellitic dianhydride IV, and trimellitic anhydride V. 

When formulating a system for optimum abrasion resistance, both the epoxy/resin hardener binder system and the filler blends used appear to have an influence. The simulation of abrasive service loads on industrial floor toppings in a laboratory is not simple, and numerous wear test machines have been devised. Correlation between different wear test machines is not always good, although most... 

The products of the chemical degradation of PETP with triethylene tetramine and triethaneolamine can be used as epoxy resin hardeners, it is demonstrated. Products of PETP aminolysis with triethylene tetramine and aminoglycolysis with triethanolamine, were characterised using NMR and rheometric measurements. Characteristics of the crosslinking process for the system epoxy resin/ PETP/amine degradation product, and epoxy resin/TETA for comparison were investigated by DSC. Three classes of liquid epoxy resins based on bisphenol A, bisphenol F and epoxy novolak resins were used in the experiments. 16 refs. 

The following coating resins were used (1) a vinyl ester (Dera-kane 470 from Dow Chemical) (2) a polyester (Atlac 382-05 AC from ICI) and (3) four epoxy resin/hardener combinations. The details of the resins and hardeners used are shown in Table I. One of the epoxy/hardener combinations was represented by materials from two sources. 

Diazocines 192 and alkyl-substituted derivatives were among lower and higher ring homologs used as catalysts for making epoxy resin hardeners and materials for elastomers, polyurethanes, paints, etc. (86JAP6133158). 

Amino and functional aromatic phosphates, phosphonates, and phosphine oxides have also been used as reactive components to impart flame retardancy to cured epoxy resins. Phosphine oxides are particularly hydrolytically stable and several studies have been reported, for example, of the curing of epoxy resins with bis(aminophenyl) alkyl and aryl phosphine oxides65-67 (Structure 5.19). The relative performances of epoxies cured with aromatic diamine hardeners containing phosphine oxide, phosphinate, phosphonate, or phosphate units have recently been assessed.68 Aromatic phosphine oxides have been functionalized also with maleimide and hydroxyl groups for use as epoxy resin hardeners.69,70... 

Bis(4-aminophenyl)methane, commonly known as 4,4/-methylenedianiline, or MDI (41), is toxic, with an acute oral LD50 (rat) of approximately 200 mg kg-1. Occupational exposure occurs by inhalation and dermal contact, particularly from its use as an epoxy resin hardener. Excessive exposure to its dust has resulted in temporary liver damage in workmen. It is a mild eye irritant and can cause cyanosis. Though it is not a primary skin irritant or strong sensitizer, skin irritation can occur with sensitive individuals. It can be handled safely if care is taken to prevent excessive exposure to dust and fumes. 

Figure 3.35. A correlation plot of rheological gel time (from crossover of G and G") and the maximum in chemiluminescence (CL) intensity over the temperature range 140-200 °C for the following epoxy-resin/hardener systems o, Tactix 742/27% DDS A, Shell 1153/22% DDS and Shell 1071/27% DDS. Adapted from Kozielski et al. (1995).

Figure 3.50. The relationship between PCI score and percentage cure as determined by DSC for the epoxy-resin/hardener system DER 332/Jeffamine T-403 in the following mixing ratios o, 100/45 and X, 100/55. Aust et al. (1997). Copyright 1997 by Society for Applied Spectroscopy reproduced with permission of Society for Applied Spectroscopy.

Characteristics of the obtained modifiers are shown in Table 4.4. The properties of compositions based on various epoxy resins, hardeners, and modifiers are shown in Tables 4.5-4.8. 

Properties of Compositions Based on Various Epoxy Resins, Hardeners, and Modifiers... 

OTHER COMMENTS used as an intermediate in the preparation of polyurethane foams, elastomeric fibers, and polyamides used in industry as a curing agent for epoxy resins and urethane elastomers, and as a corrosion inhibitor for iron useful in the determination of tungsten and sulfates has also been used in the preparation of azo dyes, as a rubber processing chemical, and as an epoxy resin hardening agent. 

Mori H, Yoshimi N, Sugie S, et al. 1988. Genotoxicity of epoxy resin hardeners in the hepatocyte primary culture/DNA repair test. Mutat Res 204(4) 683-688. 

The most widely used epoxy systems are those which are based on pure epoxy resins, hardened with a curing agent. Curing of epoxy resins containing two epoxy groups per molecule can be readily accomplished by the addition of primary polyamines, such as ethylene diamine, diethylene triamine, triethylene tetramine, tetra-ethylene pentamine, etc. Aliphatic polyamines produce cured resins with the greatest chemical resistance. However, these systems have inadequate durability, weather resistance and film-forming properties. They are sensitive to humidity, errors in addition rates are quite possible, and the catalysts are relatively toxic. 

Higher molecular weight epoxy resin hardeners such as fatty polyamides do not have the problems associated with amines and amine adducts. These reaction products of dimer and trlmer acids with polyfunctional amines provide films with fewer surface discontinuities. Polyamide cured epoxy coatings are more forgiving than amine cured epoxy coatings since they require less demanding surface preparation. Also, mix ratios are less critical for poly-amide/epoxy coatings (56). 

Methyl isobutyl ketone has become increasingly important as a chemical feedstock. The oxime is used as an antiskinning agent in oxidatively drying paints, and the peroxide is used to cure unsaturated polyester resins. Methyl isobutyl ketone is an intermediate in the preparation of imidazolones and acetal esters. It is also used to block amines (ketimines) that act as moisture-initiated latent epoxy resin hardeners. Finally, alkaline autocondensation at elevated temperature yields higher molecular mass products that are employed as fragrances and perfumes. 

Some low molecular weight chemicals, such as, the conventional epoxy resin hardener methyl tetrahydrophthalic anhydride that can stay as a remnant in the system, can cause immunologic contact urticaria . 

Nielson, PO., Properties of Epoxy Resins, Hardeners and Modifiers, Adhesives Age, Vol. 42, 1982. 

Thach BT, Chase TN, Bosma JF (1975) Oral facial dyskinesia associated with prolonged use of antihistaminic decongestant. N Engl J Med 293 486-490 Van Hecke E (1975) Ethylenediamine sensitivity from exposure to epoxy resin hardeners and mycolog cream. Contact Dermatitis 1 344-348 Vickers CFH (1961) Dermatitis medicamentosa. Br Med J 1 1366-1368... 

Uses Epoxy resin hardener curing agent for coatings, floorings permits VOC compliance... 

Uses Retarding agent in rubber compounding in alkyd resins polyester resins paints plasticizers curing agent for heat-cured epoxy resins hardener for resins insecticides mfg. of phthaleins, phthalates, benzoic acid, dyes, chlorinated prods. laboratory reagent pharmaceutical intermediate polymerization control agent for melamine-formaldehyde resins for food pkg. retarder in food-contact rubber articles for repeated use... 

Properties Colorless liq. strong fishy ammonia-like odor m.w. 159.3 b.p. 235 C flash pt. (CC) 109 C Uses Raw material for epoxy resin hardeners Manuf./Distrib. Celanese http //WWW. celanesechemicals. com http //www. chemvip. com... 

Toxicology LD50 (IV, mouse) 141 mg/kg poison by IV route TSCA listed Precaution Combustible corrosive Hazardous Decomp. Prods. Heated to decomp., emits toxic vapors of NOx Uses Gelling catalyst for PU slabstock and molded applies. intermediate for prod, of quats., plasticizers, corrosion inhibitors, textile chems., emulsifiers, oil additives, and flotation aids epoxy resin hardener Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, Haltermann Prods. UK http //www.haltermann.com, Trigon Chemie GmbH http //www.trigon-de.com Trade Name Synonyms Toyocat -MR [Tosoh http //www.tosoh. co.Jp]... 

Uses Intermediate for prod, of quats., plasticizers, corrosion inhibitors, textile chems., emulsifiers, oil additives, and flotation aids epoxy resin hardener catalyst for prod, of PU... 

Oleth-8 Oleth-12 . Oleth-15 raw material, epoxy resin hardeners N,N-Dimethyldipropylenetriamine raw material, ethers SD alcohol 13-A raw material, ethoxylation Cetearyl alcohol Coconut alcohol . Palm kernel alcohol... 

Tiitu, M., et al. 2005. Aminic epoxy resin hardeners as reactive solvents for conjugated polymers Polyaniline base/epoxy composites for anticorrosion coatings. Polymer 46 (18) 6855. 

The amine-reactive nitrile liquids are useful in formulating a modified hardener package through admixture with an amine, amidoamine or fatty poly-amide curing agent of choice (14). And novel elastomer-modified epoxy resin hardeners giving excellent reported adhesive properties have begun to appear in the marketplace (15). 

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