He n r y F. Pa l m e r, T h e X y lo s R u b b er C om pany, A kron, Ohio
A description an d interpretation o f p h y sic a l tests on raw reclaim ed rubber are presented. A discu s
sion o f the m erits o f tests on reclaim -sulfur cured com pounds versus tests of ty p ica l com pounds con
tain in g the reclaim s shows that the fo rm er are of little value, except in the case o f specific gravity.
A
C O N S ID E R A T IO N of th e te s tin g of raw m aterial such as reclaim ed ru b b e r should in clu d e b o th th e m a n u fa c tu re r’s te s ts for co n tro l purposes a n d tests ap p lied b y th e consum er to in su re him self ag a in st v a ria tio n s in raw m a te ria l p urchases. T h ese te s ts m a y be id en tical in m an y cases, b u t th e consum er m a y also ru n a c tu a l processing te s ts in his p ro d u c t a n d facto ry .
All th e larg er ru b b e r com panies an d m o st sm aller ones w ith a technical s ta ll ru n te s ts on incom ing raw m aterials.
T h e problem h ere is to d eterm in e th e m inim um n u m b e r of te s ts involving th e m in im u m of tim e a n d lab o r w hich will assure th e consum er t h a t his raw m a te ria l is uniform an d com parable to previous sh ip m en ts. I t is d ecid e d ly u n fo rtu n a te a n d costly for b o th p ro d u cer a n d consum er if th e consum er’s specification te s ts on m a n y ru b b e r com pounding ing red ien ts are in co rrectly chosen, carelessly perform ed, an d too critically in te rp re te d . T h ese fa u lts m ay be found singly or to g eth er, a n d th e technologist responsible for th e condition m ay n o t be re c e p tiv e to th e in tro d u c tio n of new ideas. A n y of th e above co n d itio n s necessarily m eans u n w arran ted rejections, inconvenience, a n d expense.
T h e o b je c t of th is p a p e r is to ev a lu a te b o th m a n u fa c tu re r’s an d consum er’s te s ts ap p lied to reclaim ed ru b b e r, a n d to suggest a sim ple, ra tio n a l, a n d p ractical pro ced u re for testin g th is com pounding in g red ien t.
A rćsum ć of th e chem ical a n d p h y sical te s ts ap p lied to re
claim ed ru b b e r is as follows:
I. C h e m i c a l T e s t s
A. Raw or uncured reclaim 1. Acetone ex tract 2. Chloroform extract 3. Alcoholic potash extract 4. T o tal and free sulfur 5. Carbon black 6. Cellulose
7. Alkalinity or acidity 8. M oisture
9. Ash 10. Ash analysis
11. Special tests—e. g., manganese, lead
I I . Ph t s i c a l Te s t s
A. Raw or uncured reclaim 1. M anual or visual 2. Smoothness 3. Milling 4. T u b in g
A testing procedure is recomm ended f o r the con
sum er o f reclaim ed rubber, which stresses process
ing an d p h y sic a l tests on cured com pounds fro m a fa cto ry test ru n {preceded by laboratory tests only i f they can be interpreted accurately), using a specific an d suitable recipe.
5. Plasticity and recovery 6. Load capacity
7. Color
B. Reclaim cured with sulfur 1. Specific gravity
2. Tensile, elongation, and stress 3. Permanent set
4. Resistance to tear 5. Rate of cure
C. Reclaim in special test formulas 1. Any usual cured rubber tests
2. Any of the tests listed under II-A on the uncured compound
G en erally speaking, chem ical te s ts are ru n fo r th e purp o se of a sc e rta in in g th e c o n s titu e n ts of th e reclaim fo r efficient com pounding. T h e se an aly ses in d e ta il are su p p lied b y th e m a n u fa c tu re r as re p re se n ta tiv e of his p ro d u c t. O ccasion
ally p u rch asin g specifications w ill lim it som e chem ical con
stitu e n ts , such as m an g an e se c o n te n t o r a lk a lin ity . In a s m uch as m o st a n a ly tic a l p ro ced u res are o r can be b a se d on fu n d a m e n ta l chem ical m eth o d s, th e figures a re reproducible from one la b o ra to ry to a n o th e r . W hile ch em ical te s ts an d la b o ra to ry pro ced u res a re im p o rta n t, th e y a re n o t, w ith few exceptions, u su ally a serious o r m u ch d is p u te d fa c to r in control te stin g as co m p ared to p h y sical te s ts. T h e re
su lts of chem ical an aly sis a re g e n erally a c c e p te d as a n in n a te c h a racteristic of th e reclaim , a n d are so u sed b y com p o u n d ers.
P hysical te s ts m u s t be classified acco rd in g to th e s ta te of th e reclaim w hen te s te d .
Ra w o r Un c u r e d Re c l a i m
T h e processing of reclaim ed ru b b e r d ep en d s up o n its condi
tio n in th e raw s ta te . T h erefo re, a n y te s ts w hich w ill in d icate its processing q u a n titie s are of g re a t value.
A m a n u a l a n d visual te s t of reclaim should be th e first a n d is th e sim p lest te s t to w hich i t m a y be su b je c te d a fte r m an u fa c tu re o r up o n pu rch ase. T h is is p rim a rily a m a n u fa c tu re r’s p relim in ary co n tro l m e th o d , b u t is, of course, applicable to q u a lita tiv e d ifferen tiatio n of v ario u s ty p e s of reclaim . D ep en d in g up o n th e ex p ertn ess of th e in sp ecto r, th is te s t reveals q u a lita tiv e ly th e softness, n erv e, color, odor, a n d sm oothness of th e p ro d u c t. I n a g iv en p ro d u c tio n ru n , a n experienced in sp e c to r can v e ry a c c u ra te ly elim in ate m a te ria l w hich is irre g u la r a n d n o t com parable to a control.
T h is te s t is m o st v a lu a b le as an index of sm oothness.
Jan u ary 15, 1934 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 57
58 A N A L Y T I C A L E D I T I O N Vol. 6, No. 1
Ja n u a ry 15, 1934 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 59 I n co m pounds of th e m echanical goods ty p e , w here o fte n
th e reclaim is th e m a jo r c o n s titu e n t of th e com pound, a definite av erag e difference in reclaim -su lfu r ten sile stre n g th m a y c a rry ov er to th e com pounds, show ing a tr e n d b u t n o t pro p o rtio n ally . T e s ts on fo rm u la IV , a s reco rd ed in T a b le V I, show a case w here th e re is a sm all b u t essen tial difference in ten sile a n d a definite difference in elongation in th e com p o und. T hese differences are in d ic a te d in th e reclaim - su lfu r te s ts b u t n o t in th e c o rre c t p ro p o rtio n , alth o u g h th e change in m a n u fa c tu re of th e reclaim should assu re th e difference, as in d ic a te d b y th e re s u lts o b ta in e d w hen th e re
claim s a re te s te d in fo rm u la IV .
Fo r m u l a IV
Blend reclaim 70.0
Sulfur l.C
Diphenylguanidine 0 .5
Lime 3 .5
Zinc oxide 1.0
Whiting 18.4
Paraffin 0 .5
Medium process oil 4 .5
100.0
Ta b l e VI. Te s t s o n Bl e n d Re c l a i m i n Fo r m u l a IV
El o n g a t i o n a t Te n s i l e
N o . OF Te m p. Br e a k St r e n g t h
Te s t o r R e c la im R e c la im R e c la im R e c la im
Fo r m u l a Cu r e St r i p s Te s t X y X Y
M in . ° C. % % K g ./sq . cm.
(1 4 1 .7 ° C .) R e c la im 100
S u lf u r 5 } 25 16
(1 5 7 ° C .)
19 370 39 0 55 65
F o r m u la IV S 16 29 185 21 5 3 6 .5 3 8 .3
T h e re su lts of ten sile-elo n g atio n te stin g o n reclaim -sulfur m ixes, th erefo re, force c e rta in conclusions:
1. With the best testing conditions and with sufficient tests, reproducible results may be obtained.
2. Under routine testing conditions which do not allow suffi
cient, tests, the results are accurate at best to 10 per cent, and will many times be less accurate than this.
3. Even the best results are not a criterion of the properties of the reclaim in the recipe in which it is to be used.
Di s c u s s i o n
T h e m a n u fa c tu re r of reclaim ed ru b b e r m u s t avail him self of a n y te s t w hich can be ru n in his fa c to ry or la b o rato ry , in as
m uch a s he c a n n o t h av e av ailab le a ll th e ty p ic a l processing e q u ip m e n t of his v a rie d consum ers. I t is fo rtu n a te th a t physical te s ts on ra w reclaim give re su lts w hich in d icate closely m o st processing conditions. T h e reclaim m an u fa c tu re r m a y also ru n processing te s ts on ty p e com pounds in w hich th e reclaim is being used, o r th ro u g h cooperation w ith th e consum er h e m a y ru n th ese te s ts in a specific te s t com pound su b m itte d b y t h a t p a rtic u la r consum er. I n th is w ay th e m a n u fa c tu re r does th e m o s t he can in th e w ay of con
tro l te stin g .
W hile th e m a n u fa c tu re r is lim ited b y n o t know ing each
specific com pound in w hich his m a te ria l is used a n d b y n o t h a v in g av ailab le each specific s e t of e q u ip m e n t su ita b le for processing te s ts on th is ty p e of co m pound, th e consum er on th e o th e r h a n d is in th e p o sition to c a rry o u t a c tu a l te s ts on h is ow n e q u ip m e n t a n d in h is ow n com pound w hich will give th e on ly acc u ra te criterio n for e v a lu a tin g a n y raw m a te ria l in clu d in g reclaim ed ru b b e r.
T herefore, fo r th e ex am in atio n of reclaim ed ru b b e r b y th e consum er th e follow ing procedure is recom m ended:
1. On a sam ple shipm ent, a small sam ple from each slab, th e whole being blended, should be used. On a carload ship
m ent current practice is generally to tak e six to ten sam ples from the car, blending these for test.
2. Chemical tests should be run for any specific constituent.
3. Specific gravity on a reclaim-sulfur mix should be obtained.
4. L aboratory processing tests on the raw reclaim and in a te s t recipe, also physical tests on the cured te st compound, m ay be made. Unless these tests are known to have a direct and accurate interpretation in reference to th e actual processing and tests on th e finished product, th ey should be om itted entirely.
5. An actual factory run of one or a few mixings of a typical compound should be made, wherein actual processing is noted and tests are m ade on the finished product.
A n y m a n u fa c tu re r w ho will follow th e above p ra c tic e is p erform ing his te s ts on reclaim ed ru b b e r recipes in th e m o st p ractical a n d m o s t satisfacto ry m a n n e r, a n d th e re s u lts o b ta in e d in u tilizing procedure 5 ab o v e are p a rtic u la rly satis
fying from th e sta n d p o in t of b o th consum er a n d m a n u fa c tu re r.
F o r m a n y y e a rs th e reclaim er h a s h e a rd h is p ro d u c t a c cused of being responsible, because of v a ria tio n , for m a n y of th e m u ltitu d in o u s ills o ccurring in ru b b e r m a n u fa c tu rin g p la n ts. A s re c e n tly as 7 y e a rs ago m a n y of th ese co m p lain ts w ere ju stifiab le. B ecause of th e progressive ad v a n c e s in co n tro l to w a rd s u n ifo rm ity of p ro d u c tio n in th e p a s t 5 to 7 years, v e ry few’ co m p lain ts of a n y k in d are ju stifiab le to d a y . E v e ry reclaim er h as had experiences in w hich h is p ro d u c t w as held culpable, on ly to be ab le to p ro v e t h a t a n o th e r fa c to r w as th e cause of th e difficulty. F u rth e r, e v ery reclaim er will a p p re c ia te know ing th e fa c ts on w hich a j u s t co m p lain t is based, since th e y m ake av ailab le to him experience a n d know ledge th ro u g h w hich h e m a y profit. R eclaim ed ru b b e r should be considered o n ly as a n im p o rta n t com pounding in g red ien t, a n d fo r th e b en efit of b o th consum er a n d m a n u fa c tu re r a ra tio n a l, p ra c tic a l, a n d th o ro u g h te s tin g pro ced u re is in d isp en sab le.
Li t e r a t u r e Ci t e d
(1) H u rle sto n , E . H ., In s t. R ubber I n d . T ra n s., 5, 348 (1929-30).
(2) K ilb o u rn a n d M iller, I n d . E n o . C h e m . , 22. 69 (1930).
(3) P a lm e r, Ib id .. 19, 1030 (1927).
(4) P a lm e r, M iller, a n d B ro th e rs, I b id ., 23, 821 (1931).
(5) S h e p a rd , P a lm e r, a n d M iller, Ib id ., 20, 143 (1928).
(6) S taffo rd , W . E ., In s t. Rubber I n d . T rans., 5, 340 (1929-30).
(7) W illiam s, I n d . E n o . Ch e m., 16, 362 (1924).
(8) W in k e lm a n n , Ib id ., 18, 1163 (1926).
(9) W in k elm an n a n d C ro a k m a n , Ib id ., 20, 134 (1928).
Re c e i v e d S e p te m b e r 2 0 , 1933. P r e s e n te d b e fo re th e D iv is io n o f R u b b e r C h e m is tr y a t th e 8 6t h M e e tin g o f th e A m e ric a n C h e m ic a l S o c ie ty , C h ic a g o , III., S e p te m b e r 10 to 15, 1933.
Ge r m a n y De v e l o p s Im p r o v e d Pr o c e s so f St e r i l i z i n g Ar t i f i c i a l Ic e. A new process of sterilizing ice has been introduced in Germany, according to a report made public by the Commerce Department. Sterilized ice has up to now been produced throughout the world by freezing sterilized w'ater, it is pointed out. This ice w-as always liable, however, to be infected during transfer from the factory to the user. There was, furthermore, the possibility of germs being transferred indirectly to the food
stuffs in ice-cooled rooms.
George Kaune, a Munich scientist, is reported to have suc
ceeded in applying his Katadyn process, consisting of the steriliza
tion of water b y the use of metallic silver, to the production of
artificial ice. The use of this process has resulted in obtaining totally different results. Artificial ice made from water treated with this process not only is sterile, but in addition has bacterici
dal qualities. For this reason, it is being designated in Germany as “activated ice” to distinguish it from ordinary artificial or natural ice.
Careful bacteriological tests, carried out at the Hygienic Insti
tute of the Dresden Technical University are said to have proved that germs introduced into the melting water of activated ice were killed after a few hours, so that the certain destruction of any bacteria that come in immediate contact with the ice may be safely relied upon.