vIO.^ 



THE INDIA RUBBER WORLD 



Februaky 1, 1921 



AGING OF VULCANIZED PLANTATION RUBBER 



THE FOLLDWiNC is quoted from a report by IJr. H. P. Stevens,' 

 The investigation was supplemental to a former one carried 

 out with the usual rubber and sulphur mixing containing ten per 

 cent of sulphur because it was desired to ascertain how far the re- 

 sults thus obtained hold good for mixings containing other in- 

 gredients of technical importance. For this purpose a series of 

 progressive cures was made with a mixing consisting of 60 parts 

 of rubber, three parts of sulphur, and 37 parts of zinc oxide. The 

 tests were carried out with three different types of raw rubber. 

 namely: (1) plantation pale crepe, (2) plantation smoked sheet, 

 and (3) fine hard Para as a control. The vulcanized specimens 

 were subjected to physical tests at intervals over a long period, 

 and the percentage of combined sulphur was determined shortly 

 after vulcanizing and again after an aging period of three and 

 one-half years. The vulcanized specimens were preserved in a 

 dark cupboard, but were not otherwise protected from atmos- 

 pheric agencies. 



In previous reports it was shown that a rubber vulcanized 

 with ten per cent of sulphur, with no other ingredients, is ap- 

 proximately stable when preserved under ordinary atmospheric 

 conditions for two or three years, provided that the coefficient 

 does not exceed three units. Under these conditions the break- 

 ing strain improves over a period and then gradually decreases, 

 but only very slowly. The vulcanized rubber may therefore be 

 regarded as aging satisfactorily from a technical standpoint. 



The present results show that the figure for the safe limit of 

 the coefficient must be revised in the case of rubber compounded 

 W'ith five per cent of sulphur and a filler. ' In this case the rubber 

 with a coefficient of three units shows fairly rapid deterioration 

 on prolonged aging. After one year the rubber with this co- 

 efficient has reached the maximum breaking strain and has fallen 

 again to approximately its original value. During the second 

 year the rubber loses abovit 30 per cent of its original value, 

 after which the breaking strain decreases more slowly and the 

 curve tends more to the horizontal. The approximately stable 

 specimens are those cured to give a coefficient of two or a little 

 higher, certainly not higher than 2.5 units. 



In this connection it may be noted that a cure giving a co- 

 efficient of three or thereah( uts for the rubber compound with 

 ten per cent of sulphur will give a coefficient of about two units 

 for the rubber compound with five per cent of sulphur and filler. 

 It may be that the period and temperature employed in vul- 

 canizing are factors affecting the stability of the vulcanized 

 product. Further experiments are required before any definite 

 conclusions can be reached. 



Comparing the three types of rubber, smoked sheet and fine 

 hard Para give curves more similar in ai)pcarance to each other 

 than to pale crepe. The loss in tensile strength of the aged sam- 

 ples of the latter is more pronounced than with either smoked 

 sheet or fine hard I^ara. With this type of mixing, smoked sheet 

 shows up particularly favorabU' as compared with pale crepe, 

 and confirms the general impression obtained from previous ex- 

 periments in which mixings containing zinc oxide were compared 

 with the usual rubber sulphur mix. The latter type of mix. 

 although suitable for general purposes, cannot be taken as imi- 

 versally representative of all types of mixings. It is not merely 

 a matter of dilution with inert constituents and resulting diminu- 

 tion of effect. It has been found, for instance, that zinc oxide, 

 ordinarily regarded as an inert mineral, has nevertheless the 

 power of activating certain organic accelerators in a remarkable 

 degree. It is, therefore, not surprising that zinc oxide should 

 bring out differences between smoked sheet and pale crepe which 

 are not apparent when tests are made on mixings containing 

 rubber and sulphur only. 



TREATMENT OF CRUDE RUBBER WITH STEAM 



The treatment of crude rubber with live steam' is claimed to 

 provide a convenient process for eliminating the variations in the 

 physical condition of raw rubber as received from the plantations 

 as well as a convenient method of drying rubber. 



According to the invention the raw rubber to be treated may 

 be placed in a suitable container provided with means for the 

 exhaustion of air and the introduction of steam. The steam 

 pressure used varies according to the duration of the treatment, 

 from 10 10 15 pounds per square inch for seven hours, to 60 

 pounds per square inch for three hours. For any particular lot 

 of rubber the best results are obtained by taking viscosity tests 

 fro^n a sample. 



VISCOSITY TEST 



The viscosity test above mentioned may be made with one per 

 cent of rubber in benzol in the following manner : 



A sample of the steam-heated rubber is dried in a suitable oven 

 at 100 degrees F. It is then cut in small pieces and shaken in a 

 flask at intervals until the rubber has completely dissolved. It is 

 then allowed to settle and the solution carefully decanted into a 

 viscometer of the Ostwald type. The test is conducted in a water 

 bath thermostatically controlled. 



PURE ANTIMONY PENTASULPHIDE 



Most grades of antimony pantasulphide contain calcium 

 sulphate in proportions ranging from 30 to 55 per cent. Some rub- 

 ber goods manufacturers object to the presence of calcium sulphate, 

 owing to its water of crystalization, and nearly all recognize its 

 defect as a filler on account of the relatively large size of its 

 particles. The Rare Metal Products Co., Belleville, New Jersey, 

 has developed a pure penlasulphide of antimony, free from adul- 

 teration, and containing 16 per cent free sulphur. It is claimed 

 that this material will produce a handsome red tube of fine texture 

 at a cost lower than when the adulterated product is used. 



'The Bulletin of tli- T?nl,l,rr r.rnwers' Assoriation, Tulv, 1920. Volume 

 2, Xo. 4. Page 270 



THE REDUCTION PRODUCTS O- PARANITRANILINE RED AS 

 VULCANIZATION ACCELERATORS 



By Andre Dubosr 



When paranitraniline is treated with nitrate of soda in the 

 presence of hydrochloric acid, a diazo combination is obtained 

 which with a solution of ^-naphtolate of soda generates para- 

 nitrobcnzene-azo-yg-naphtol or paranitraniline red, the formula of 

 which ma>' be written thus: 

 OH 

 C„,H„ < > N — CcH.NG, 



N 

 This body is well known by dyers and calico printers, who 

 cause its formation on the textile direct, by foularding the fabrics 

 in a solution of ^-naphtolate of soda, followed, after drying, by 

 immersion in a solution of diazoparanitranilinc. 



Paranitraniline red under reducing action, particularly of hydro- 

 sulphites or of aldehyde sulphoxylates, reduces and divides, form- 

 ing two bodies, amincnaphtol and paraphenyleiie diamine, both of 

 which are excellent accelerators. The reaction takes place ac- 

 cording to the following equation : 



OH 

 C,„H ,„ < > X — C.H.NO. J- 5 (Na.S-.0.. 2CH,0) -f 8ILO = 



N 

 Paranitraniline red Sodium aldehyde sulphoxylate 



OH NH, (1) 



10 fNaHSC) + 10 (CHuG) + C,oH„ < + C.,H, < 



NH., NH,. (4) 



Aminonaphtol Paraphenylcne 

 diamine 

 Thus by the action of hydrosulphites two powerful accelerators 

 can easily be obtained from a well-known coloring matter and 

 this method is general for all combinations of naphtolates with 

 diazoted amines. 



'Ilritisli pnlcni No. 150.04J. 



