Document yk9OKdnj6dBpdzJ6E7yXB4R7E

/LY' ^ ') KETIil TO MIHSHMi UBOHATOIK L IIFEIEiCI COW mt o rm COgglDERTIAL me mo r a n d u m r e p o r t n o . m-t is PREPARED BY: H. S. EASTLACK 16* Dr Graves, Vila. Mff in j. B. Bullitt, 3 Turn D. MCBurfcey, "n R. B. Thornes, Newburgh E, A. Rodman, Newburgh B, B. Davis, Lab. Russell Morgan, Lab. P. B. Evans, Lab. P. Robinson, Lab. 0. H, Bullitt, lap. Sta Milm. W Dr Lawson, Lab. H. Q. Stauffer, Lab. Library (5), Lab. Patent Section, Lab. Piles 1810 Marshall Laboratory July 15, 1954 "ADXPBEKB" AS A COATING POLYMER Introduction* The writer visited the Jackson Laboratory on July 1 to develop further information on the possibilities of wAdiprene" for coating purposes. Persons interviewed were: Summary: J. w. Libby, Jackson Laboratory Brio Barthel, " " J. A. Nelson, " " E. K. Gladding, " " ... J. S. Rugg, Rubber Laboratory Proa the information obtained, it sees doubtful that it will be possible to prepare coatings from Elastomer 1 solutions that have all the properties of "Adlprene" p bIo t stoeScjT unless elaborate precautions are taken to rigidly exclude water, act. only from the materials used, but also during the curing operation. Nevertheless, films cured in contact with atmospheric moisture iwy still be sufficiently tough and abrasion resistant to be of Interest for coatings. N35497 A more likely approach to coatings that can be applied by practical means appears to lie In the use of the '*prepolyair5?i or a recently developed latex* Tough, abrasion resistawlTIls can fee prepared by rather simple techniques from the prepolymar. Such films cure fey reaction with water In a humid atmosphere, or they can fee cured fey passing through a diamine bath. The latex deposits a film which is similar chemically to uncured Elastomer 1, but higher in molecular weight. Tough, rubbery films are ob tained without curing, or they may he cured by passing through a TDI bath. Action? 1. H. 0. Stauffer and the writer will undertake to character ise films from solutions of Elastomer l, the prepolymer, and the latex. 2. Kewburgh`s attention is called to the possibility f using the prepolymer or the latex for fabric or webb coating. Discussions WMaistrv of "Adlorene* {Confidential); The first step in producing Elastomer M ("Adiprene'' Rubber Stock) is to prepare a "prepolymer" by reacting toluene diisocyanate (TDI) with a polytetramethylene glycol having fa molecular weight of about 3000? frepolymer (TOT) The prepolymer (0CJ3-P-HC0) is then reacted with water to extend the chain length and to produce an unstahllaed polymer? 0C2?jV*ISH*CG`HH*pJ *$H-C0*M*P`ISC0 DUP030003705 3 - This is stabilized by terminating the chain with piperidine to produce Elastomer 21 (mol. wt. 30*000). Elastomer H, contains 1% of phenyl 0 naphylamine (flIireozone,, D) as an anti oxidant. Other elastomers can be prepared by using different polymeric glycols, and by extending the prepolymer chain length with diamines. However, Elastomer N (water extended) appears to be the one on which Orchem is concentrating most of their effort. Curing of Elastomer N with D1 takes place by abaction of the -NCO groups with the -HHp groups. Dhder anhydrous con ditions the reaction may be represented as fololwss J!H*C0*MH H CO T ICO v-- HH*C0*HH - H*C0*EH ------ CO m e T HH Ce O In the presence of water, some of the TDX reacts with itself to produce longer crosslinking chains, e.g., I/ M*CO'HH-T`HH*CO-HHeT*HH*CO23H"T*NH'CO*H The polymeric structure obtained in the presence of water is there fore different from that obtained under anhydrous conditions. Preparation of Films from Elastomer H Solutions; Elastomer N picks up 12 of water under normal storage conditions and should therefore be dried before use, by milling for 10-20 minutes on a 2-roller mill. The disappointing results of Marshall laboratory work with films sprayed from solutions of Elastomer M in dimethyl formamlde (BMP), may have been due to (!) the fact that the Elastomer was not dried, (2) the effect of atmospheric moisture, (3) the BMP was not redistilled to remove traces of amines, and (4) DMF reacts with TDI. Tetrahydrofuran (THF) is a better solvent for Elastomer E than DMF, particularly when mixed with either chloroform or dichlopoethylene, The THF should be absolutely dry, free from per oxides, and the stabilizing agent present in the material as sup plied by Elchem must be amoved. DUP030003706 4 TDI-urea (OCM*T,HB,CO<,HH*T'HCO) is a better curing agent than TDI, producing tougher films, but is insoluble in THF. It was suggested that we try both TDI (in solution) and TDX-urea (in suspension), using 4 and 8 parts per 100 parts of Elastomer H. Knife coating was suggested in preference to brushing or spraying to minimize oontact with atmospheric moisture . Flash drying should also be carried out under conditions involving minimum exposure to moisture. Curing for 15* 30, and 60 minutes at 130C. and 5-15 minutes at 110*0. was suggested (shorter curing time results in a higher modulus). Films should be aged 1-2 weeks at >50$ H.H. before testing, to allow for "after curingB. Motes 35)1 is very toxic (maximum safe concentrations 0.1 p.p.m.). Hence it should be handled with extreme care, and curing ovens should be vented to the outside. Reinforcing agents may yield tougher, more abrasion re sistant films. HAF carbon black, and Cab-O'-Sil (SlOg) are best. From 15 to 30 parts per 100 parts of Elastomer M were suggested* The Elastomer should first be warmed up on a rubber mill before adding the extender. The stock is removed from the mill at inter vals, allowed to cool and the operation repeated until a cut sur face is glossy. The Tabor abrasion test does not measure resistance to abrasion as related to tire wear. All Jackson Laboratory tests for this service are made by road-testing tires* Use of "Frepolymer" as a Film Formers The prepolymer, as described above, reacts rapidly with water and must therefore be kept absolutely dry until used. Jackson laboratory will supply samples blanketed with dry nitrogen in sealed bottles. Once opened the entire sample should be used immediately or discarded. The prepolymer (TOT) is a liquid having about the con sistency of honey. It contains some free 93)1, Films can be mad by knife casting without dilution. It is readily miscible with THF, or with a 50/50 mixture of toluene and either MEK or MXBE. From 10-20 parts of solvent should toe sufficient to reduce TOT to brushing consistency; 20-30 parts, to spraying consistency. The latter two methods of application will, of course, involve more contact with atmospheric moisture before the film is laid down, than knife coating. Films of TGT cure in 1-4 days at 50$ R.H. and 80*F,, but at least 7 days should be allowed before testing the film. Such films are comparable with nylon in the Tabor abrasion test. TOT films can also be cured by contact with diamines, e.g., m-phenylene diamine. ' DUP030003707  -a* "Adlprene" Latex: A latex has been prepays by diapering the prepolymer in wafer. Reaction of the water with the terminal - MCO groups extends the chain to form a polymer similar chemically to un cured Elastomer N, but higher in molecular weight. When this polymer is separated from the latex by filtration, washed to re move water soluble dispersing agents, and dried at room or slight ly elevated temperatures, a tough rubbery film is obtained. It can be cured, if desired, by dipping in a solution of TDI. It should be possible to prepare films from this latex by casting on glass, or spreading on fabric or other substrates. A sample is being obtained for evaluation along this line. The film forming properties of this latex are said to be much better than those of the amine-extended latex of which we previously had a sample. HEE sAX 7-14-54 H. E. EASTLACK P.S. The following two reports have been received and turned over to the Marshall laboratory Library: Haskell Laboratory: "Report on the Toxioity of Toluene - 2,4-pilsocyanate (TDI)", Rubber Laboratory: MA procedure for Determining the Concentration of TDI and TDX-Urea in Air". DUP030003708