January 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
Ilespite the iiistakJility (if the resins a t high temperatui~eno 'evidence of the slightest tlecomposition is observed in storage at room temperature. N o odor of sulfur dioxide is noted on opening cartons of the finely divided resin powder that may have been in Ptorage for several ycars, and pioces m o l d d from the resin show no app:trent change in propei,ties wit,li age. The polysulfones can hc) molded sat,isfactoiil>-by compression methods a t temperatures ranging from 225" to 325" F. Satisfactory moldings are ohtained under these conditions even in the absence of a st.abilizer. Despite the fact that the t,emperatuw is sufficiently high to promote a considerable amount of deconiposition a t atmospheric prrwure, depolymerization is prevented by the pressure exerted on the ma in the molding operation. If the rrsin has been t,horoughly before use, polished steel molds may be used with no tt1)parent evidence of (-omsion. Some degree of success h i s been realized also in injec-tion moldiiig tests v,-it,hemulsioii-l)ol~meriee~ polysulfones. lT8ing:I 1-ounce laboratory prcss, it, w w 1)ossihle to establish conditions for molding unstabiliecl I-butene polysulfone satisfactorilj,. In larger equipment,, hoxevc\r, the higher temper:tt,urc:s and greater amount of a o r k done on the resin bring about excessive decomposit,ion of the unstabilized materid. For hct'ter results a I-butene-ethyl acrylate-sulfur dioxide berpolymer 0011 ta,ining a stabilizer such as zinc diliwryl dithiophosphatc. is required. Blends of polysulfone resin with IIycar rubber ~tahilizedin this way have been evaluated also in injection molding tests. Encouraging results '~ycreohtaincd iii commercial equipment opemt-
165
iiig a t temperatures up to -100" F. Generally speaking, pol!-sulfone resins and resin blends have been molded by injection a t cylinder temperatures of 370' to 390' F. and mold temperat,ures of 175" to 195" F., but molding temperatures may deviate xidely from these figures depending on thc size and design of the molding machine and die. ACKNOWLEDGMENT
Thc authors gratefully acknowledge the contribution of
J. F. Hon-e, R. J. Fanning, J. A. Delap, I.. D. Jurrens, the lnte IC. u'.Cottcn, and others who 1)articiptLtt:d in t,hin experimental program and of W.H. Rrj.nolds aiid the late V-.A. %Iiulze ivho dircc%edt,lie ao1,k. LITERATURE
crrm
(I) Croucsh. W.W., and Howre. .J. F. (to Phillips Petroleum C o ) , C . S. Patent 2,556,799 (June 12. 1951). ( 2 ) Dainton, F. S., and Ivin. K. ,J., Suture, 162,S o . 4122, 705 (1948). ( 3 ) Dainton, F. S., and IJ-in, K. ,J., Proc. Eoy. SOC..212, No.AllO9. 207 (1952). (4) blarvcl, C. S., and Weil, E. D.. ,J. A ~ JChem. ?. SOC.,76,61 (1954). (5) Scribner, A. K., and Wilder. E'. W.(to Phillips Petroleum Co.), U. S. Patent 2,453,039(Xoreniber 2, 1948). (6) Snow, K . D., and Frey, F. E., 1x1).EN+.& E x , 30, 170 (1938). (7) Snow, 13. D., and Frey, F. E., d . A m . Clzem. Soc.. 65,2417 (1943). IIIICEIYED for review J u n e 4, 1954.
ACCEPTED September 1. 1954, Prpsented before the Division of Paint, Plastics, and Printing I n k Chemibtry at tlic 125th Meetin8 of the .41iirnrc.is C ~ r ~ \ r r c SOCIE:TY, .~a~ Kansas City, 310.
Evaluation of Commercial GR-S Vulcanizates by a Creep Test J. G. LICHTY, R. B. SPACHT, AND W. S. HOLLINGSHEAD Research Laboratory, Goodyear Tire und Rubber Go.,Akron, Ohio
c
ERTAIN difficulticls ariw in rating the stability of GR-S
vulcanizates by air oven, air bomb, and oxygen bomb aging when direct measurement of modulus, elongation, and tensile is used to ascertain the evtent of degradation. GR-S vulcanizates are morr stable to oxidation than are natural rubbrr vulcanizates; 1icnc.e it is more difficult to show diffeiences between various stockb. In natural rubber during th(. early stages of degradation chain scission predominates, a hilc in GR-S the opposite reaction of crosslinking predominates. I n natural rubbrr vulcariizates the degree of change of moduluf and tensile may be consideidbly greater upon aging than in GII-S vulcanizates, making it more difficult to draw conclusions in the latter case. Furthrrlnort,, Neal and Ottenhoff (8) and Shelton and Winn ( 10 ) point out that it is very difficult to obtain corielations between the various methods of accelerated aging in either natural rubber 01' GR-S vulcanizates. It is therefore desirable to have other methods than conventional aging tests to rate GI%-Svulcanieates. Creep is one such method. Mooney, Wolstenholme, and Villars ( 7 ) shon cd that the btress relaxation of rubber as caused by oxidation. Tobolsky, Prettyman, and Dillon (f2)suggested the use of stress decay as a means of rating the resistance of rubber storks to deterioration. Throdahl ( 1 2 ) used creep to evaluate antioxidants in natural rubber and GR-S vulcanizates, and pointed out the particular advantage of a creep test in rating antioxidants in GR-S vulcanizates. Among others making contributions to the study of creep were Gehman (6) and Pedersen and Nielsen (9).
The American Society for Testing Materials Committee )-11 adopted a creep test as a tentative procedure for rating the stnhility of rubber vulcanieatps in 1952 ( 2 ) . For this study hot and cold GR-S polymers containing the five commercially used antiouidants-I'I~SA, B-L-E, Agerite Stalitcl, Polj7gard, and King Stay S-mere selected (TabIe I). Thew basic polymrrs \+ere developed l o meet certain cornmrrcial needs for nondiscolored, slightly discolored, and discolorcd rubbers. TIRLEI. c;It-s Polyiiicr QR-S 1000 GR-S 1001
GR-SI006
GR-S GR-S GR-R GR-S GK-S GI
