In order to study the behavior of such ions as Fe3+, Zn2+, Cr042- and PO43- during electrophoretic painting, procedures for their isolation and analytical methods have been examined. The radioactive ions were added to the mixture of an electrophoretic paint and a solvent (mixture of xylene and n-butanol), extracted from the non-aqueous layer of the mixture, and then separated into individual ion. The reliability of this procedure has been confirmed by the measurements of radioactivity. Extraction of Fe59, Zn65, Cr51 and P32 from the non-aqueous layer.-The ions composed of these radioactive elements were washed out with nitric acid. The yields of Cr51, Zn65 and P32 were at least 95 %. The yield of Fe59 could not be checked due to its weak radioactivity. Isolation of Cr51 from the nitric acid layer by precipitation of Fe59, Zn65 and part of P32. Cr51 in the nitric acid layer was oxidized with H2O2, then the solution was neutralized in the hope that P32 might be co-precipitated with Fe59 and Zn65 leaving only Cr51 in the solution. The result was not satisfactory because the concentrations of Fe59 and Zn65 were too low to give quantitative precipitations. The amount of Cr51 remained in the liquid layer was as high as 98 %. Ether extraction of Fe59 from the hydrochloric acid layer. It was confirmed that more than 95 % of Fe59 in the 6 N-HC1 solution of Fe59, Zn65 and P32 could be extracted. The amounts of Zn65 and P32 remained in the solution were 96 and 91 %, respectively. Isolation of Zn65 with an anion exchange resin. Zn65 present in the 6 N-HCl solution together with P32 was isolated with an anion exchanger (Cl-type) as ZnCl3-ion and recovered by treating the exchanger with distilled water and 0.1 N-HNO3. The amount of Zn65 recovered was close to 100 %. The amount of P32 removed from the solution was only 2 %. It is clear that the procedures for the precipitation are the key to the reliability of the proposed methods of isolation. It is desirable that the concentrations of Fe59 and Zn65 in the solution are at least 20 p.p.m.
Aromatic-amine hardeners impart high deformation temperature, excellent chemical and electrical properties to cured epoxy resins. One of the disadvantages, however, is that some are solid at ordinary temperature and must be heated to melt before use. We have prepared liquid hardeners which gave to cured, epoxy excellent properties comparable to those of the aromatic-amine cured epoxy. Fluidised forms of m-phenylenediamine were prepared by reacting at least 3 parts (by mole) of phenyl-, allyl-or butyl-glycidyl ether with 10 parts of m-phenylendiamine at 100-120°C for 6 hr. The fluids with these compositions are essentially stable solutions of m-phenylenediamine in the adducts of m-phenylenediamine and the ethers. The storage stability of these fluids was excellent even at a temperature lower than 10°C. Viscosity of the adduct mixture had a minimum value at the (m-phenylenediamine/ether) mole ratio of 100/33; the adduct mixtures with this mole ratio were thus employed as hardeners for an epoxy resin (bisphenol A-epichlorohydrin condensation type) with molecular weight of about 380. The resultant coatings possessed the electric, thermal as well as chemical resistances which were comparable to those obtainable from m-phenylenediamine and better than those obtainable from Epikure Z. The weights per one mole of available hydrogen atom of the adducts of m-phenylenediamine with phenyl-, allyl-and butyl-glycidyl ethers are 47, 43 and 44, respectively. These adducts in combination with triethylenetetramine or tetraethylenepentamine can be applied to the drip process as suiltable hardeners. The adducts prepared by reacting less than 3 parts (by mole) of the ethers with 10 parts of m-phenylenediamine were solid. The effects of the glycidyl ethers on various properties of the cured epoxy resins and the adduct eutectic mixtures are compared with those in the casting systems where the glycidyl ethers are used as diluent.
Flame retarding effects of four halogenated alkyl phosphates (β-chloroethyl-, β-bromoethyl-, dichloropropyl-and dibromopropyl-phosphates) were studied. on the casting systems of bisphenol A-epichlorohydrin condensation type epoxy resins. The epoxy resins (mol. wt. 380 and 310) were cured with such hardeners as triethylenetetramine, methylbicyclo (2, 2, 1) heptene-2, 3-dicarboxylic acid anhydride and BF3-monoethylamine complex. These resin systems were compared with those obtained from halogenated bisphenol A-epichlorohydrin condensation type epoxy resins (halogen= Cl, Br) such as Epichlor E-5 and DER-542 Resins. Self-extinguishing time (ASTM D 635-56 T) for these casting systems decreased with increasing halogen content in cured epoxy resins. When β-chloroethyl-phosphate was added, for example, the chlorine contents (eq. /g.) and the self extinguishing times (sec.) for Epikote 815/triethylenetetramine system are : 5. 4×10-4, 150-210 ; 9. 5×10-4, 30-60 ; 13. 2×10-4, 8-10 ; 17. 4×10-4, 0.0×10-4O Hologenated alkyl phosphates were much more effective than the halogenated bisphenol A-epichlorohydrin condensation type epoxides. Comparisons were made between the chlorinated bisphenol A-epoxy resin and its brominated analogue, and it was found that bromine was more efficient than chlorine as flame retardant under the test conditions. For instance, the weight fractions (%) of the halogenated epoxy resins to the total resin weights and the self-extinguishing times (sec.) for Epikote 828/triethylenetetramine system are as follows : C1-20, 8-19 ; C1-40, 6-15 ; C1-60, 5-10 ; Br-10, 8-13 ; Br-20, 4-9 ; Br-40 3-5. The addition of large amounts of these phosphates, however, resulted in cured epoxy resins with poorer mechanical properties. This is contrary to triphenyl phosphite which improves compressive strength as well as dimensional stability of epoxy adhesives and castings.
The efficiency of Tele-Solv, stripper for cured epoxy and polyester resins, was studied as stripper for epoxy-resin coated electric wires (cured with amines) and for transformers casted with resins composed of bisphenol A-epichlorohydrin condensation-type epoxy (mol. wt. 380) and polyamide resins. Gas chromatographic and infrared spectral analyses indicated that the stripper was a mixture of various halogenated (Cl or Br) hydrocarbons, alkyl and alkylene halides, ethers and ketones. Although this stripper was effective when applied to the casting materials with large amount of resins, or with somewhat a great strain, it was not very effective when applied to the wires which were thin-coated. In the e. case of the transformers, the cured epoxy-polyamide resin castings were stripped completely without any heating or mechanical operations within about 8~10 hr. On the other hand, the cured resin layer on the electric wires was removed completely only if a mechanical operation was applied after the wires had been kept immersed in the stripper for a few hours at room temperature. The stripping efficiency of this stripper was compared with those of pure halogenated hydrocarbons such as trichloroethylene, methylenechloride, chloroform, trichloroethane, propyl bromide, ethyl bromide, and pure ethers and ketones. Various combinations of resins and hardners were also compared. On the basis of the analytical results on Tele-Solv and of recent theories of the solvating and stripping powers of chlorinated hydrocarbons, attempts were made to discuss the effects of the shapes of coated or casted materials, of the kinds and amounts of hardeners, of the curing conditions and of the test methods on the stripping power of Tele-Solv for the cured epoxy resin-hardener system.