1312
* *****
INDUSTRIAL A N D BNQINEERINQ CHEMISTRY
***
Vd. 34, N a 11
Data obtained in the LaboratorJr and on the factory-mixed stocks are given in Table I. The Y value correlsteswell with
be trouble in getting a gmd factory mix but, if such a mix is obtained, subsequent processing will be eatiaf.tactry.
A series of chargea made in regular factory operations were checked in the laboratmy for viscosity, Y value, and tubing i n k . The same chargea w e v ~then mixed into tresd Btoclrs in the factory and treade were tubed t h u g h a plate die.
the degree of black dispersion (determined mimmopidy) and the exhaion temperature. There h also good correlation between faobry tubing d t a and predictions based on a combination of viscosity, Y value,and tub= index.
Ebonitp r *from Hycar
OR45 B. S. Garvey, Jr., and D. V. Srbach The 8. F. Goodrich Company, Akron,
Ohio
1
_ _ .je#om Hkar Impact and tensile strengths are as high ahhose of ebonites m d e from natural rubber. The sdkning *mperatures are considerably higher. The optimum amount of sulfur is 35 parts per hundred parts OF rubber. Accelerators may be used. This paper reports the effect of various amounts of sulfur, of accelerators, and of a variety of softeners and pigments on the tensile strength, impact strength, elongation, hardness, and softening temperature of ebonites made from Hycdr OR-I 5. Hi$-quaIit:
... .. ..
OR-15.
4s
n
T
HIS study waa underbhn to determine some of the important c Y m a c M c s of ebonites made from EIycar OR-IS and to obtain fun& mental compoundingdata which could be used for the development of commeMial stocks. The effecta of variations in amount of sulfur and the &e& of some acceleratorn, softeners, and pigmenta have. bean investigated. The multa of the i n d g a t i o n have shown that ebonites from Eyw ORA5 have phyaical properties equal to thoea of natural rubber ebonites and in addition have comidmblyhigher softening temperature. Theee nynthetic ebonites also take a high polish and may be made in varioun colorn by using colored inorganic pigmenta such 88 iron and chromic oxidea, antimony sulfides, asdmium de nide, etc.
w.
m.LIyu
I
M&od All compounde were mixed on lzinch Lsborstory milla in total batcb ai.esrsnging from 600 to IO00 grame. Hard rubber strips, 0.26 X 1 X 6 inch-, were p d , aswed, and ground to &a for the vtuioun teata. The trannverae impact tests were run on cut and b d e d pieces measuring 2.5 X 0.5 X 0.25 inch. The teet pieces were packed,in crushed ice for one hour prior to teating to ~ a 8 u t ‘ ~
Figure 1. Effect of Sulfur Ratio
I .
1
N&,
1942
**
INDUSTRIAL AND BNGINEERING CHEMISTRY
******
1313
with the degm of cure but variea little with increasingamountaof8ulfur. The StKmgth W h e S the EXpected level with only 30 parts of ~Ulfur,and little advantage, fmm a tenaie standpoint, can be seen by increasing the Bulfur content. Impact Btrength reachea the level of 112 pounds at 36 parts of sulfvr and remains fairly constant at the higher adfur ratios. The elongation tends to drop Off Sulfur bcressed and, aa would be expeoted, is noticeably l o w e d aa the time of cura is incressed. The heat combination of physiosl properties wan found in the compound with 36 plvts of sulfur at the lmminllte cure; thus, this is probably the optimum amount of sulfur for practical w, provided no materiala m p m t in the compound which tend to retard ou18. CL'~B~BBslightly
.
mMlU
I
0
Figure
9.
Effect
of
.
0
.
Accelerdtion
uniform temperature. The piece was then broken by
a
pendulum which the aample with an impact of 11 feet per second aa specified in A. 9. T. M. designation D25634T. The Werence between the initialenergy of the pendulum and the energy remsining after the impact h exp d in inch-pounds per quare inch Bample 88 impact
Strength.
Hardness waa measured with the type D Shore durometer. %ftening temwatura waa determined by ~ ~ p p o r t i nag test piece at both ends with a weight in the center and then heating in a circulating air oven at ~tdadilyin& temperatures until deformation took plsce. Sulfur Ratior
Figure 1 shows the dab obtained with H y d w mixtures when the amount of aullur waa varied from 2' 0 to 60 parts per hundred of rubber. The Boftening temperature increaees with the time of cure and also with the amount of sulfnr, at least up to 45 parts of sulfur. The bardneea in-
Aecelwation In most pmduction wmpoundu practical curing times must be obtained by the w of d e r atom. Figure 2 &OWS the &wta of inorganic and organic acceleratom when used with a Hyc8rSulfur bssa compound wntaining 35 parts of sulfur per hundred park rubber. The organic a+ celeratom are Listed in Table I. The softening temperature waa determinedfor only a part of these compounds. With the excaption of litharge, the inorganic oxides have some accelerating action. Menu i m and tellurium have a little amalerating action but seem to be partidarly advant a g e o u s o n l y i n -raising the softening temperature. The aldehyde amines and the thiocarbamate typea have a accelerating action and at the m e time maintain the good physical proprties evident in the pure gum blsnk w n b i i no accelerator.
1314
*+***+
INDUSTRIAL A N D ENGINEERING CHEMISTRY
**,
V d 34, No. 11
ance, are particularly advantageous for manufacturing acid-pmf equipment such BS battery jars. IRON OXIDE produces excep tionally high tensile strength coupled with fair elongation, high impact strength, and high softening temperature. Thin pigment also aids in mixiner by smoothing out the batch and impartiing a degree of tackiness. It is recommended for molded articles where little machining is necwwy. Zma OXIDE is closaly comparable to iron oxide except f o r i t a retarding e f f e c t on CUI%.
WHITWO produrn good impact strength, very high softening temperatm, and g o d procstacks. It is considered one of the better pigmenta. H Y ~ EBONITE R OB “EBONAB” DUST wea produced by curing sheets of the 100 part Hycar-35 part sulfur compound for 80 minutes at 320” F., then grinding to 1oOmesh. Tbepigmentproved to be a useful filler, producing good tensile strength, fair elongation, and huh softening temperatures. This pigment is recommended for extruded goods and for articles which have to be mSChined. H ~ B RUBBER D DUST pigmented compounds are lower in tensile and elongationt h similar Hycar dust compounds,presumably b e c a w of the poorer diapemibility of the n a t d rubber in Hycar OR. A S B E ~ Tfillers, ~ S ea would be expected, show erratic physical properties and sharply reduced elongations. However, they might prove to be useful fillere for special compounds.
‘e
Figure 3.
Effect of Pigmentation
Effect of Sokenan
Pigmantati
The effect of Merent loadings of w v d common pigments is shown in Figwe 3. AI1 compounds repmnted.were cured w) minuten at 320’ F., except hard black and zinc oxide (marked with an asterisk2 which because of their r e t m h g effect were cured 120 mmutes at 320’ F. whiting, iron oxide, Bemireinforcingcarbon black, and hard Hycar dust are the most promising pigmeuta from the standpoint of physical properties. Hard rubber dust aud asbestos can dm be used. Becsuee of ita a c i d - d i n g properties, clay is one of the most widely used pigments. &ANNEL BUCK retards cure and is difficult to process, 80 is not recommended ea a pigment for Hycar hard rubber. SEMIACTIVE BLACKcompounds are d e r to procees, exhibit rather high softening temperahma, but otherwi%eoffer no outstsnding admu*., CJAY compounds &bit rather poor physical properties but, because of their relative eaee of moldingmd acid &st-
Synthetic rubbers are not 80 tacky ea natural r u b h . For n and becsuse of their low plasticity, a considerable amount of softener is d y nBoes881y to impart good proeasing charactariatics to the compounds. F i i 4 was dram from data showing the effecta of a number of the more common softening materials. AU compounds were cured for 80 minutes at 320” F. except the Thermoprene compound. It was necessary to cure this compound 120 minutes at 320” F. for comparable reaulta beoauee of the retarding action of the Thermopreue. For maximum tsnsile strength the beat softeners in this study are dipolymer oil and dibutyl metacresol, while for heat &stance coal tar and rosins are best. For incrensed tackiness it is @vhble to uee a mixture of cod tar, cumar, or dihutyl metacresol with a light ester type aoftaner such as dioctyl phthalate, or even a blend of these three. The total quautityof soften~rusedshouldbekeptataminimumtoensu
this m
N,-
1942
* **
INDUSTRIAL
AN^ E N G I N I . M I N G
CHEMISTRY
** * * * *
freedom from pomsity, and for the eame reason volatile types of ma-
terialashouldbeavoided. F x g m 4 comparee softeners in quantities of 15 parte per hundred of rubber which is suflicient to bring out their merent pmpertiea; however, ea high 88 30 psrte may be used in actual production. Compounds containing high quantities of aoftener often re quire a @lightinrreaee in sullur content for adequate cum. DCSJGNINQ A COMPOUND. A compound suitable for a battery jar might be built up 88 follows:
A compound suitable for highquality small molded piecea, such ea gaskets, etc., might be d e w e d along the following lines:
Figure . . , .,. .. .,,,
I
.
4. Effect of Softeners ,. . : . : . , _:,: ,
..
.
.,
*
4
,
,
. .. .
.,
.
,
I
1315
