I N D U S T R I A L A N D ENGINEERING CHEMISTRY
302
Vel. 20, No. 3
iBr
20
40 STKE.55 I N KGS./SQ.
CM.
60
Figure 4
Figure 5
ranging from 2 to 5 per cent for 18 hours without showing any noticeable decrease in tensile strength. For example, dumb-bell test strips of linemen’s protector shield stock were exposed, unstretched, a t room temperature to ozonized oxygen which contained 0.5 to 1.0 per cent ozone. The strips were 3/32 inch (2.4 mm.) thick and the test section 0.25 inch (0.6 cm.) wide. The lack of change is indicated in the following table:
Strips cut from smoked sheet as received from the plantations exhibited maximum cracking a t 30 per cent elongation as determined by visual inspection.
DURATION
TENSILE STRENGTR
ELONGATION
Conclusion
The similarity of the results obtained under various tensions in sunlight and in an atmosphere containing ozone is striking and may be significant of some progressive change in the structure of the rubber which renders it a t a certain point unusually susceptible. The study here outlined is incomplete, but is presented in the hope that it may give other investigators an added method of studying problems connected with the structure or with the oxidation of rubber.
Analysis of a Typical Angle Abrasion Machine’ w. w. vogt THBGOODY$AR TIRS& RUBBERCOMPANY, AKRON, OHIO
The machine employed consists of a driven abrasive in the prerious tests they wheel, the rubber test piece in ring form being pressed would have been found. Acwriter has attempted . to evaluate the power against the flat face of the wheel in such a manner cordingly a machine was conthat the plane of the ring makes an angle with the structed of the same type as consumed in causing abrasion tangent of the abrasive wheel at the spot of contact. used in the previous tests, but of rubber. Two separate inProvision is made for measuring the power consumed so arranged that the power vestigations were made; in in abrasion by a Prony brake method. This angle maconsumption could be measboth cases the abrasion machine is essentially a constant-power machine. The ured directly by the Prony chine used was of the angle relationships between abrasion loss and time, load, b r a k e p r i n c i p l e used by type, wherein the periphery speed, angle, power consumption, etc., are given. An Williams, of a rubber ring was pressed analysis of the forces involved is also given. against the flat surface of an Description of Machine abrasive wheel in such fashion The essential features of the machine are shown in Figure 1. that the plane of the ring was perpendicular to the face of the abrasive wheel and set a t an angle to the tangent of the abrasive The test piece, A , is mounted on the freely running bearing, wheel a t the point of contact. The power and energy figures B , which can be set so that the plane of the ring can make were obtained from readings of the current supplied to the elec- any angle (0 to 90 degrees) with the tangent of the abrasive tric motor used to drive the abrasive wheel. On both occa- wheel at the point of contact of the ring. The point of consions it was found that, for a wide variety of practical tread tact is coincident with the axis about which the holder swings. stocks, the differences in power consumption were less than the The support arms can rotate freely on ball bearings around experimental error (which was not more than 5 per cent), the shaft, C, of the turn table on which the abrasive wheel, D, even though the abrasion resistance of the stocks in question is mounted. This is an alundum wheel, 36 grain. 9flexible varied more than twofold. It was concluded that as a prac- strap. E , is attached to an arc of proper radius, F , and the readtical proposition the energy concept of abrasion was of little ings of the force are obtained from the spring balance, G, reading directly to pound.3 The minimum load on the test importance in differentiating various stocks. Recently Williams2 showed differences between stocks of rings is, of course, the weight of the attachment (6.72 kg. such magnitude that it was believed that had they occurred or 14.8 lbs.) and this can be increased by adding auxiliary weight W . The mechanism for rotating the abrasive wheel 1 Presented before the Division of Rubber Chemistry at the 74th and air jets for cleaning its surface are not shown. Meeting of the American Chemical Society, Detroit, Mich., September 5 to
A
T VARIOUS times the
10, 1927.
* I n d . Eng. Chcm., 19,
674 (1927).
8 All readings of force were taken in English units, but have been converted to the metric system to conform with the publisher’s policy.
_. I I'r,)iiy liralie eqri:iiion :applies:
3
"TYFL
4504 r. I>. m. of abrasive wheel I; lorce = spring balance r e d i n g in kg. L = length of lever arm in mcters = 0.21 iiletcrs timc of test in minutcs I k r x y in kilowatt-hoiirs = kw. X -. i'orwr in kilowatts =
where .\.
.,
h,x.p.i ~.iox' T,oao Tlie volunie loss is practically proportional to the load, and the power consumption increases less rapidly than the load. (Table I1 and Figure 2)
hi:
= =
m h i e II rsioek 11: time, 10 minuter; speed, 80 I p . m.: angle. 20 dcgrees; lohil, ";tr*8ble)
Pow&%1,059 PFR
Iili
STOCK in: I."hD, iB.1
Figure I---Anelc Abrasion Machine
.I _lie :dirwimi T:L~ICE Eire obtained tis volriinc his i n cubic witirnrlt~rs,a n d from these the ciilric centiiiieters per kiloir-:itt-hour are oht.aincti. These calculations :ire idcutirnl w i t h t,lmse OS \Villi:irns. Description of Test Samples and Scope of Tests
' h c e docks :kt their corroct technical cure were used i lrmighout this work; L: sufficientnurrrRer of rings wrre r:ured nil :ill riiips were aged at, least m e week before testing. t w h I is a first-grtide black tread stock, stock 11 a serondpr~idt.t r e d nml stook 111 a third-grade stock. 'l'lie dimensions of the rubber test ring were: o. d., 8.$3 em. (3.5 inches); i. d., 5.1 em. (2.0 inches); width, 1.8 ~111. (0.7 inch). The caperimental work involves variations in angle from 5 degrrm to 86 degrees, in load from 6.81 kg. to 24.5 kg. (15 to .54 pounds), and in speed from 36 to 112 r. p. m. of the abrnsire wlieel, corresponding t o surface speeds of froin 46 i r i 143 inrters (150 to 4T0 feet) per minute.
Table I ( S l w k 11; load, 10.2 k ~ . :~ u g l r ,20 degrees; speed, 80 r. p. variable)
20
30
VOLVM IASS ~ CG.
11.25 22.1 34.1
RATSOY WIIAR cc./min. 1.15 1.13 1.14
Posse WOIti !l8 95 95
18.8 20.0
7.28 7.20
22.2
21 D s G r t i m b
20.5 21.2 21.0
20 8
806
ns5 452 1070
o i c SPEEO-Table 111 shows that the furcc ia'iuila
