May 1949
-
INDUSTRIAL AND ENGINEERING CHEMISTRY
ball milling, however, caused a raising of consistency and lowering of powder density. Apparently, the immediate effect of the grinding action was to knock off the sharp corners of the crystals so that they could fit together more compactly. However, further grinding merely caused the normal fluffing or powdering effect observed with materials of fine particle size. Grinding overcame the tendency of this plaster to settle abnormally from a water-plaster mix. Pilot plant operations were carried out in the New Brunswiclr, N. J., plant of Johnson & Johnson in 1944. Here the plaster was made in a 75-gallon steam-jacketed autoclave. CONCLUSIONS
As a result of research work on orthopedic plaster bandages a process for making a high strength, low consistency plaster of Paris was developed. The same process was independently discovered by Haddon and Cafferata. A gypsum slurry was autoclaved in the presence of a few tenths per cent of certain dicarboxylic acid salts t o produce plaster of Paris of the desired short, principally rodlike crystals. According t o conditions of autoclaving, the kind of added salt, and the concentration of the added salt, various specific crystalline forms of plaster could be produced. The effects of certain variables on the characteristics of plaster have been presented.
1065
ACKNOWLEDGMENT
This work was undertaken at the Mellon Institute of Industrial Research as part of a program of investigating orthopedic plaster of Paris on a fellowship sponsored by Johnson & Johnson. The authors wish t o acknowledge also the work of Gilbert IGvenson in the preparation and testing of samples. LITERATURE CITED
(1) (2) (3) (4)
Brookby, H. E., U. S. Patent 1,370,581 (March 8, 192d). Brothers, W., Brit. Patent 757,649 (April 19, 1904). Gardner, H. F., U. 5. Patent 1,996,372 (April 2, 1935). Haddon, C. L., and Cafferata, B. J., Brit. Patent 563,019 (July
26. 1944). ( 5 ) Hoggatt, G. A., U. S. Patent 1,960,538 (May 29, 1934). (6) Ibid., 2,002,945 (May 28, 1935). (7) Ibid., 2,067,762 (Jan. 12, 1937). (8) Kelley , K. K., Southard, J. C . , and Anderson, C. T., U.S. Bur. Mines, Tech. Pager 625 (1941). (9) McAnally, 5. G., U. S. Patent 1,713,879 (May 21, 1929). (IO) Randel, W. S., and Dailey, M. C., Ibid., 1,901,051 (March 14. 1933); 1,931,240 (Oct. 17, 1933). (11) U. S. Gypsum Co., Bull. 1.G.L.-ID. RECEIVED Maroh 11, 1948.
Cellulose Acetate Butyrate Strip Coating Compositions C. J. MALM, H. B. NELSON, AND G . D. HIATT Eastman Kodak Company, Rochester 4 , N. Y .
In recent years wide use has been made of melt dipping as a method of applying plastic coatings to protect articles from corrosion and abrasion. Thermoplastic polymers compounded with plasticizers, resins, waxes, and oils have been used. In the present work a commercial high butyryl cellulose acetate butyrate is tested with several plasticizing agents, and the physical properties of these compositions are measured.
T
H E use of strippable protective coatings has received increasing attention in recent years (1, 8,7-9). This type of covering is generally applied by dipping the article to be protected into a molten composition and withdrawing. The dipped article receives a uniform, heavy coating which quickly sets on cooling to allow immediate storage or packing for shipment. No volatile solvents are used, and so solvent curing and recovery are not required. The previous practice of wax or grease coating followed by paper covering is superseded by a single-step operation. Not only is the dip covering quickly applied but i t is removed with equal ease. A cut is made to start the “peeling” whereupon the whole covering may be removed, generally in a single piece. This type of coating serves not only to exclude water vapor and prevent corrosion but also to offer protection against handling damage. The stripped coating if kept reasonably clean may be reused by remelting in the hot dipping pot. Of the several thermoplastic polymers suggested for these coatings, ethylcellulose (1) and cellulose acetate butyrate are outstanding because of their heat stability, compatibility, and high strength. Availability, cost, and uniformity are additional factors leading to the use of compositions based on cellulose derivatives.
The following work is confined to a description of compatibility and physical properties of compositions made using a high butyryl cellulose acetate butyrate. This type of material was chosen because of its good heat stability and wide compatibility with inexpensive plasticizing agents. The analysis of the particular type of mixed ester used showed 5 t o 7% acetyl and 47 t o 50% butyryl ( 4 ) . This represents a product with a n average of 0.5 acetyl, 2.4 butyryls, and 0.1 hydroxyl per anhydroglucose unit of cellulose (2). Two different viscosity levels of this ester were used. The main emphasis was placed on a low viscosity ester having an intrinsic viscosity of 0.9 measured in acetone and designated as AB5OO-1. Some duplicate runs were made with a material of higher viscosity with intrinsic viscosity of 1.3 and designated as AB500-5. These types of esters have viscosities of 25 and 125 centipoises, respectively, when measured a t 25’ C. on 10% solutions in acetone. Although the specific aim of this work was to develop strip coating formulations, the more general purpose was to investigate compatibility and physical properties as influenced by additions of various agents. The method of attack was t o select readily available and inexpensive addition agents, test their compatibilities with the cellulose acetate butyrate, and then study these compositions with a testing program chosen t o detect good strip coating properties. Widely differing values may be obtained for tensile strength, per cent elongation, shatter temperature, and the like depending on the kind and amount of addition agents used. These differing data m e all useful, for as applications vary, the emphasis may be successively on tensile strength, shatter temperature (low temperature flexibility), and per cent elongation. No single composition has all the good properties; therefore, the choice is usually determined by a compromise.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1066
TABLEI.
Vol. 41, No. 5
COXUERCIAL STAKDARDS 300-3jO lb./sq. inch
TENSILE STRESGTH BND ELONGATION. Tensile test pieces of the folloving special dimensions (in inches) were punched out from the film with a die (t,ensilc die KO.I ) .
Figure 1.
Width of grip section JT-idtli of center flat section Length of center flat section Gage length (test marks)
0.25 2.23 2 .OO
Distance between grips Over-all length
4 .OO 6.00
1.00
Grip section tapers to center flat section by arc of 1-inch radius Marked with grease pencil o n center flat section
The tests were made on a Scott tensile testing machine (Model DH2) having a cross head speed of 3 inches per minute. The tensile strength is computed from the maximum load applied during the testing; elongation, from the total amount of travel between gage inarlrs at the time of rupture:
Four Types of Drainage
TESTING PROCEDURES
Preliniinara observat,ions m r c made on plastic granule6 coniprising the low viscosity cellulose acetate butyrate (AB500-1) and 25% of mixed plasticizer (3 t o 2 ratio by m i g h t of dibutyl sebacate to butyl stearate). This composit,ion, available commercially in the form of granulat'ions for melt coating (5j, offers a nonbulky starting mat>erialcontajriing sufficient active plasTiCiZer to aid in compatibility. Melts were made using grariules and modifying agents in ratios of 1 to 1 and 2 to 1. IIeat stability and compatibility n-ere determined by heating. ties of these melts a t 160" C. for 8 hours. Several nated by this Lest. The reinailling compositions mere made up in larger quantities and melt cast for tests. I'REPARATIOX OF TESTSHEETS. Test nielts were prepared j n 100-giam lots by mixing the ingredients with a stirring rod in a beaker and heating in an oil bath at 180" C. Gentle intermittent stirring prevents whipping in air and allows melt formulation in 2 to 3 hours. Films were rast a t about 0.030-inch rhiclmezs by spreading the niolten material on an 8 X 10 inch glass plate m t h a coating knife. Test pieces n-ere then c u t from the films.
Tensile strength =
brcalcing load (lb.) __ width (inches) X thickness (inches)
yo Elongation over 2-inch gage marks
=
[inches between gage marks at point of rupture - 2 )
- 100
2
h second arid i d r r tensile die ( S o . 2) was later made to increaw the cross section of the test piece. This gave spccirneris of the following dimensions (in inches): K i d t h of grip section Width of center flat section Length of center flat section Gage length (test marks) Distance between grips Over-all length
1.30
1.00 2 23 2.00
4.00 6.00
The tensile values obtained with thcse two dies d o not agree. The larger die ( S o . 2 ) probably gives more accurate values because of its greater cross section. SHATTER T E M P E R A T U RCast E . sheets 4 X 8 inches in size were suspended in a circulating air box cooled bv drv ice (constant temperature dry ic'e c a h e t , Model 4-3352, American Instrument Company). The temperature o i t,he box \m,s dropped by 10" F.increTABLE 11. P H Y S I C i L PROPERTIES O F CoXlioSITIOXS USINGPLASTIC G R A N r L C S ments and allowed to hold for 20 to 30 Ratio of minutes. Each test sheet was then Granules St ability, to Tensile, Elonga- Shatter 2 4 Hr. crushed x i t h gloved hinds. The temModif3;ing Lb./Sq. tion. Temp., Sxeatat perature was recorded at which the epecihIodifying Agent Aperit In. 'z F. ing 160' C. Sheet Appearance iiien shattered t o bits. This meaiureDioctyl phthalate 1:1 0 35 Below merit is easy t o make arid is lairlp -.!in - Cnnd Clear reproducible. Temperatures above the Clear 2:l 20 45 -GO Good Opaque Butyl stcaratc 1:1 0 5 70 Good shatt,er point may cause stiffening of the Clear 2:1 120 35 -20 + Good sample without inducing sufficient britClear Castos oil 1:l 65 63 -60 + Good tleness for shatter. Clear 2:1 170 70 -40 + Good Crumbly 1:l STT-EATING. Amelt cast sheet was hung . . Soybean ail Opaqne io; 6J Good -io 2:1 at rooin temperature and obscrved at S1. dark Clear yellow 1.1 0 10 -- 20 10 Corn oil the end of 1 week. Surface droplets or a 61. dark Clear yellow 2:1 200 70 Clear yellow Good 1:1 170 110 0 gc~ieralsurface haze which could be wiped Aroclor 5 4 4 P Clear yellow Good 2:l 243 - 10 90 off was ident,ified as sweating. Clear yellow Good 1:l 415 10; 30 Aroclor 5460a STABILITY.A portion of the melt was Clear yellow Good 2:l 10 400 80 held at, 160" C. for 24 hours in mi open 81. dark Clear yellow 1:1 85 - 20 lbalynb -I 122: 1 70 - 30 81. dark Clear yellow test tube. The color of the resulting 1:l Brittle 70 , . . Synthe CopalC sample was noted. Composit'ions made 70 Brittle 2:l .. 81.' dark Grainy, yellow u-ith stable ingredients show rio vis1:1 0 33 - 20 Paraplex RG-94 S1. dark Grainy hazy 2:l 110 60 - 10 cosity or physical property change as Good 1:l 0 35 - 50 Clear, i a n Paraplex G-2.P long as the color of the melt remains Good 2 1 0 Clear, tan 00 - 60 good. Opaque, brittle Curnar W'-l/ne 1:1 70 .. . iPi Dark color 70 2:l 10 APPEARANCE.The cast sheet was es91: dark Opaque, brittle 1:l 70 Lewiaol KG.2 1 , . . amined for color and homogeneity. 2:l iio 5 70 S1. dark Grainy, yellow Opacity and graininess indicated limited Opal was0 1:l ... ... 70 ... Opaque, very brittle Good 2:1 630 25 30 Opaque compatibility . BLOCKIKG.A blocking test, was run a Chlorinated biphenyls, hlonsanto Chemical Company. hj-stacking 1-inch squares at 50" C. under b Methyl abietate, Hercules Powder Company. C Glycerol ester of abietic acid. a 3-pound weight. The following numerid Polyester compounds, Resinous Products and Chemical Company. cal ratings describe the behavior: (,1) e Coumarone-indene, Barrett Chemical Company. no blocking; ( 2 ) slight blocking, easily J Maleic modified rosin ester, Hercules Powder Company. 0 Hydrogenated castor oil. pulled apart; (3) firmly tacked but may be pulled apart; and (4) sealed I I
. ^ _ _ _
.
.
I
May 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
gives fairly good tensile values. Modifying agents of low solvent power tend to give rigid sheets. As examples, butyl stearate and Opal wax show poor low temperature flexibility, this behavior being accentuated as the ratio of plasticizer to granules is increased. Solvents of a more resinous nature such as the chlorinated biphenyls (Aroclors) give excellent tensile strength, although a drop in low temperature flexibility is noted. (The term resin is used here t o designate mat,erials which have in themselves some film-forming qualities.) All these compositions were in Class 1 for blocking.
PROPERTIES OF ESTER-MODIFIER COXPOSITIONS TABLE 111. PHYSICAL AB500-1,
Elongation,
Shatter Temp.,
Stability, 24 Hr. at
Block-
%
In. % O F. 160° C. 0 35 -80 Good 35 50 0 55 -60 Good Castor oil 35 0 55 -60 Good 50 245 80 -40 Good 50 Dark Aroolor 5442 35 520 70 50 1010 80 50 Dark Aroclor 5460 35 Too brittle t o cut .. .. 50 Too brittle t o cut Abalyn 35 100 105 '0 Gobd 50 370 100 0 Good Hercolyna 35 BO 105 -10 Good 50 350 100 -10 Good 0 Hydrogenated methyl abietate, Hercules Powder Company. Modifying Agent Dioctyl phthalate
v
Tensile, Lb./Sq.
ing
., 1 1 3 4
..
.. 2 1 2
DRAINAGE. For this test machined steel plates 2 X 3 X 0.125 inch mere dipped to about a 2-inch depth in the bubble-free melts. After a B-seoond immersion at each of the test temperatures, the plates were withdrawn and the drainage was noted. Figure 1 shows four different types of drainage. Compositions types 1 and 2 according to this test are desirable, as and as complete as possible drainage hastens the operation and eliminates a finishing step. COMMERCIAL STANDARDS
Because of the special propert,ies such as high elongation and stripping shown by this type of composition, other physical properties differ from the normal standards of thermoplastic ~ I presents b l values ~ which the acceptable materials. ~ range of properties (6). COMPOSITIONS USING PLASTIC GRANULES
The melt-coating granules previously described were first tested with a series of modifying agents as shown in Table 11. Good solvent modifying agents such as dioctyl phthalate give sheets of very low tensile strength but excellent low ternperature flexibility. Castor oil, although a good solvent,
TABLE IT'.
Appearance Clear, colorless Clear, colorless Clear, colorless colorless Clear, Clear, yellow Clear, yellow Clear, yellow Clear, limht yellow yellor+, Clear, lizht $ellow Clear, light yellow Clear, light sei^^^^,
..
1067
SIMPLE COMPOSITIONS USlNG LOW VISCOSITY CELLULOSE ESTER
The formulations using granules indicate the wide variation of properties possible and point to the need of careful formulation to achieve a balance of properties. Because the presence of plasticizers in the granules probably tended to mask the effect of the modifying agent, a two-component series was made using members from Table 111 shows the marked effect of the modifying agents on tensile strength and shatter t'emperature. Dioctyl phthalate again yields soft, weak films having extremely low shatter temperatures. Films with zero tensile strength can still be easily handled but fail t o record on the tensile machine. Castor oil, which is likewise a good solvent, improves tensile values while maintaining - low temnerature flexibilitv. The chlorinated biphenyls (Aroclors) produce compositions of considerable rigidity which tensilewise are strong but break on sharp impact. Compositions with the abietic acid esters (Abalyn and Hercolyn) are intermediate in properties, having average tensile values and fairly low shatter temperatures.
PHYSICAL PROPERTIES OF M O R E CONPLEX B L E N D S
Composition
AB500-1
Aroclor 5460 40
:: 45 30 20 10 45 25 15 20 10 25 15 40 30
B. 50 50 50 50 50
20 20 20 15
50 50 50 50
15 20 15 15 15
50
a
15
Castor oil 10 20 10 20
.. .. ..
Abalyn
..
..
20 30 40 20 40 50
DiocRust tyl preHer- phthal- ventive colyn ate oil
.. ..
..
20
io
20 20
10 20
30 2 0' 10 30 20 10
.. ..
..
, .
Drainage 170° C. 3 3 1 1 1
.. .. 30 40 40 50
1
.. 10 20
io
190' C.
..
, .
..
..
io
. I
30 20 10
..
, .
..
..
Tensile values in closures obtained using wider teusile specimens.
2 1 2 1 1
Tensilea, Elon- Shatter Sweating, Lb./Sq. gation, Tzmp., 16 Hr. 140' C. In. % F. a t 50' C. 4 810 65 50 3 360 76 40 3 70 .. 3 iii 50 235 3 70 ... (Very brittle) 3 i oo 40 785 2 110 20 475 3 70 (Very brittle) 1 iio 40 360 1 20 60 140 3 40 90 655 2 30 110 510 1 150 375 40 1 115 130 20 4 110 780 50 3 95 460 20
-
+
-
Stability, 24 Hr. a t 160' C. Dark Dark
2
2 3 3 2 2
795 610 420 550 480(500) 380(500) 400 690 (6 10) 370(550) 350 (520)
90 100 90 110 110 95 00
105 75 100
50 30 20 20
0 - 10
10 10 10 - 10
-
-
++
+++
4
3
OK
'3
OK
'3'
OK OK Dark
a
OK
I . .
3 3 3 3
Blocking. 3 Lb./ Sq. I n . 16 Hr. a t 50' C.
3 ..
OK Dark Dark
3 3 3 3 1 4 2
..
4
..
2
Dark 0 IC
..
.. .
I
..
..
..
.. ..
2
2
2 2 2 2 1
1
INDUSTRIAL AND ENGINEERING CHEMISTRY
1068
Her3olyn
Rust preventiye oil
..
..
Aro. clor 5460 20
Cas-
..
Ibalyn 30
20
10
20
,
20
20
10
..
tor
oil
..
15
30
15
10
20
l-5
20
10
20
20
10
I
..
.. .. 3
..
5
..
5
..
..
15
..
..
30
6
15
10
..
20
5
15
20
10
7
..
..
50
..
..
..
..
45
..
B
..
..
..
50
..
’.
..
..
45
1
..
a
b
*.
TABLE V. RESULTS OF CORROSION CYCLE
-
Coinpositiona
40
..
10
..
40
10
AB500-1, 60% composition. Sealing at the lap in all cases OK.
Vol. 41, No. 5
Dip Temp. C. 190 170 140 190 170 140 190 170 140 190 170 140
Thickness, Inch 0.072 0.072
190
170 140 190 170 140 190 170 140 180 170 140 190 170 140 190 170 140 190 170 140 190 170 140 190 170 140 190 170 140 190 170 140 190 170 140
After 10-Day Cycle Tests Rust Flexibility None OK, no blush _
_
I
_
_
_
~
Clarity Good
Stripping Cracks, no oil spots
0.068 0.069 0.076
Good
OK, dry
Very tiny rust spots a t seal
OX, no blush
0.068 0.069
Good
OK, dry
None
O K , no blush
Cuts fairly easily
0,075 0.067 0.077
Good
OK, dry
None
OK, no blush
Cuts hard
0.064 0.076 0.094 0.069 0.074 0,082 0.068 0.075 0.091 0.067 0.071 0.082 0.069 0.071 0,084 0.066 0.069
Very good
Very good 113 oily
OK, no blush
Cuts easily
OK, no blush
Cuts easily
OX, dry
Splotch a t lap Small spot None None 1 blotch None None
OK, slightly oily
h-one
OK
Cuts easily
Good
OK, d r y OK, slightly oily
None
OK
Cuts easily
Good
OK, slightly oily
None
OK
Cuts easily
0.060
Good
OK dry
Kone
OK, no blush
Cuts easily, tacky
Good
OK oily fipots
None
O K , no blush
Cuts easily, slightly tacky
Good
OK, dry
None Slight rust spot Very few tiny spots None
OK, no blush
Cuts easily
OK, no blush
Cuts easily
...
Remarks b Hard t o cut, slightly tacky, tends to shatter on out Cuts with slight difficulty
...
Very good
OK 1/s
Poor Dark Dark Good
oily
OK
Cuts easily
0,082
0.076 0.076 0,060 0.064 0.077 0.069 0,072 0.101 0.060 0.072 0.105 0.056
0.077 0.113 0.066 0.072 0.109
Very good
Very good oily
1/3
Very good
OK, oily
Light rust i n oil: Wipes clean
OX, no blush
Cuts easily
Very rood
OIL oily
None
OK, no blush
Cuts very easily
MORE COMPLEX CORIPOSITION S
The need for blends of the abovc ingredients is evident. High tensile values are desirable but of limited use in the face of brittleness in the cast sheet. Accordingly, compositions were made to achieve a balance of desirable properties. The cellulose ester &.as tried a t both 38 and 50% to maintain a maximum of tensile strength. Aroclor 5460 (a yellow solid) was used because it imparts melt fluidity without causing a serious tensile loss in the cast sheet. Plasticizers \yere added in quantities sufficient to secure low temperature flexibility yet avoid low tensile values. A limited amount of rust preventive oil (Colonial Beacon Oil Company, WS-548 rust preventive) mas incorporated in some cases to secure quicker setting, easier stripping, added rust prevention, and a lowered blocking tendency. Table I V presents data on these blends. Section B demonstrates the use of rust preventive oil. Section C gives values for compositions free of resin. The added property of drainage is included with specific reference to melt dip application. ESTER, RESIN,PLASTICIZER BLEKDS. Compositions in section A (Table IV) comprise the ester, a resin, and a plasticizer. An ester level of 5070 as compared with 35y0 calls for a higher operating temperature (note drainage) but improves the tensile strength. High quantities of Aroclor 5460 maintain the tensile
strength at a high level and yet give melts of good fluidity. The flexibility a t lower temperatures (shatter temperature) is not good. It is evident t h a t a balance must be arrived a t betn-een tensile strength and impact strength (flexibility), ADDITIONOF RUSTPREVENTIVE OIL. Section B (Table 1V) introduces some four- and five-component melts which represent attempts a t balancing properties and a t the same time presents compositions in which 5% of rust preventive oil is substituted for a similar amount of Aroclor 5460. The use of some Abalyn with the Aroclor 5460 reduces the brittleness tendency but the shatter temperature is still high. Progressive increases of castor oil in place of Abalyn improve shatter properties but lower tensile strength. The use of the nonsolvent rust preventive oil in place of Aroclor gives acceptable low shatter temperature values with loss in the tensile properties. 4 s oil compatibility is limited some sveating is observed. Although in general this may be undesirable, for the specific application as a protective coating this is useful; a thin oil layer reduces corrosion possibilities. Duplicate runs using Hercolyn in place of Abalyn show similarity in properties. Section C (Table ESTER, PLASTICIZER, OIL COMPOSITIO~YS. IV) introduces some very simple formulations using the inexpensive abietic ester plasticizers with additions of rust preventive oil. Tensile values are in a medium range with shatter
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
May 1949
temperature figures desirably low. Sweating has increased with concurrent good blocking behavior. The poor solvent action of the oil calls for somewhat higher dipping temperatures. In this group Hercolyn seems to show slightly better properties than Abalyn. PROTECTIVE COATING EVALUATION
A selection was made of some of the better formulations, and these were applied to panels and put through a corrosion cycle. Three machine steel panels were dipped in each composition using successive temperatures of 190°, 170", and 140' C. to apply increasingly heavy coats. A 0.50-inch lap joint near the middle of each test piece allowed a test of sealing a t a lap. These samples were then subjected t o a 10-day cycle, each day consisting of: 16 hours in a chamber maintained a t 100" F. by a current of steam; 3 hours in an ice-salt bath; 2 hours in a 120"F. air oven; and 3 hours in 5% salt solution at room temperature. At the end of the cycle the panels were examined for rusting, and the coatings for clarity, stripping, flexibility, lap seal thickness, and cutting qualities. Ease of print reading through the stripped coating measured clarity. Easy parting of the coating from the metal was required for good stripphg. The metal surfaces were then examined for rusting and also for evidence of oil sweat on the surface. The coating should fold without breaking for satisfactory flexibility. Folding at the lap seal tested the bonding. A measurement near the center of the dipped coating recorded thickness. It can be seen (Table V) that the dipping temperature effects coating thickness. This difference i s most marked in compositions having quick setting behavior (see those high in rust preventive oil). Clarity was good and lap seals satisfactory, as the joined surfaces actually fuse. All except the first composition stripped well, leaving the metal either dry or with a small amount of exuded oil. Rust was at a minimum or absent entirely. Flexing is sometimes accompanied by a blush a t the fold indicating a condition of limited compatibility. None of these coatings showed this type of blushing. An observation on ease of cutting was made, since the coating generally must be cut to start the stripping. This behavior is of importance in the temporary storage of instruments such as thread gages which cannot be roughly handled during stripping. RATING OF COMPOSITIONS
No. 1 rating a t 190" and 170' C Others Tensile. Above 500 Ib./sq. in. 350-500 200-350 Shatter temperature. -20' t o 10' F. 00 to +IO0 f20" t o 4-50' Blocking. None Slight Sealed Stripping. Very good Good Poor Rust. None Slight Clarity. Very good Good Ease of cutting. Good Poor
-
COMPOSITIONS WITH HIGHEST STRIPCOATING
Composition No.
AB500-1
Aroclor 5460 Castor oil Sbalyn Hercolyn Rust preventive oil Drainage Tens i1e Shatter temperature Blocking Stripping Rust Clarity Ease of cutting Rating
RATINGS 1
2
50 ,
.
50 15
45
10
5
5
1 1 2 0 1
1 2
..
Grade 1 0 2 1 0 2 1 0
1 0 -2 1 0 -2
Using this system the compositions in Table VI were chosen aa the best. A rating of 10 points is possible.
3 50
20
4
5
6
15
50 15
50 15
50
.,
20
30
40
20 10
..
5
1 0 1
1 1
0
1
1 7
8
I
.
5
.
5
1
1
1 1 0 1 0 1 6
50 15
., ..
.. ..
10
1 1 2 0 0 1 1 1 7
1
1
1 2
10 20
I
1
0 1 0 1
0 2 1 0 1 0 1
6
6
1 0
.
,
0
5
1 1 1 0 1 0 1 1
6
U S E OF HIGHER VISCOSITY CELLULOSE ESTER, AB500-5
To secure increased tensile properties and improve toughness, melts were made of the compositions listed in Table VI but using AB500-5, the ester of higher viscosity. Table VI1 includes only properties where measurable differences would be expected. The tensile values were obtained using the wide tensile specimens (die 2) and should be compared with similar measurements in Table IV (values in closures). Compositions made with AB500-5 call for higher operating temperatures (Table VII) because of the greater melt viscosity. Cast sheets show an average increase of about 50% in tensile strength and 25% in elongation. Coatings are accordingly tougher with the higher viscosity ester and would be more useful in abrasion resistance. Low temperature shatter values are not changed appreciably. Some stripping difficulty is encountered because of the increased film tenacity.
TABLE VII.
PHYSICAL PROPERTIES OF COMPOSITIONS CONTAINING AB500-5
Comp. No.
190' C. 170" C. 140' C. 4
.3.
Because of the difficulty in rating compositions following such varied measurements, a grading system was set up Eight properties of practical significance were chosen Points were given for degree of excellence. In cases of bad behavior such as poor stripping or blocking, a heavy negative penalty was imposed t o be certain the composition was removed from the running. The grading system follows: Drainage.
TABLE VI.
lo69
4 3
Tensile, Lb./Sq. In. 740 765
780 805 1000 845 860
Elongation.
%
125 125 115 125 120 125 120
Shatter Temp.,
F.
- 10 - 10
- 20 +25 10
+-30 0
Stripping OK
OX OK OK
OK tough OX: tough OK
The foregoing data made clear the need of compromise in compounding. The low viscosity ester yields melts of good fluidity which offer rust preventive coatings of varying tensile strength and flexibility depending on the choice of compounding agents. The higher viscosity acetate butyrate forms more viscous melts, but the coated films are extremely tough and hold more promise for long time storage or for shipping uses. LITERATURE CITED
(1) Anon., Modern Packaging, 17,64-70 (February 1944). (2) Fordyce, C. R.,Genung, L. B., and Pile, M. A., JND.ENG.CHEM., ANAL.ED., 18, 547-50 (1946). (3) Gould, B., Iron A g e , 155,66-7 (June 14,1945). (4) Malm, C.J., Nadeau, G . F., and Genung, L. B., IND. ENG.CHEM., ANAL.ED.. 14. 292-7 (19421. (5) Malm, C.J., Salo; M., and Vi;ian, H. F., IND.ENG.CHEM.,39, 168-74 (1947). (6) Ordnance Depi,'U. S. Army Tentative Specification AXS-1167, Rev. 2 (May 29, 1946). (7) Prine, W.H., Modern Plastics, 22,116 (December 1944). (8) Waring, C. E., Modern Packaging, 19,143-7 (February 1946). (9)Ibid., 19,204-7 (March 1946). REcmrvED March 16, 1948. Presented before the Division of Paint, Varnish, and Plastics Chemistry a t the 113th Meeting of the A M ~ R I C ACNH ~ M I C A L SOCIETY, Chicago, Ill.
