A Relative Hazard Classification of
ORGANIC PEROXIDES DAVID C. NOLLER STANLEY J. MAZUROWSKI GILBERT F. LINDEN
FREDERIK 1. C. DE LEEUW ORVILLE L MAGELI
TABLE 1.
18
RELATIVE HAZARD CLASSIFICATION OF COMMERCIAL ORGANIC PEROXIDES
I’NDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
a
are a class of commercially 0rganic available ‘ peroxides chemicals which are unique in their
*
stability characteristics and potential hazards. The very properties which make organic peroxides valuable to industry require that these materials be iandled and stored with caution. w h i n used under :ontrolled conditions and in the proper chemical environnent, commercial organic peroxides are easily handled and used to initiate desirable free radical reactions. If free radicals are formed while peroxides are stored in concentrated form, an accelerated decomposition may result, leadmg to the release of considerable heat and mergy. Any one peroxide formulation may have a lifferent manner of decomposition from another formulaion of the same peroxide. These facts, and the generaion of a complexity of by-products even in the simplest :xamples, make classification of hazards a difficult Rtbject. A relative hazard classification system for organic Ieroxides is now proposed which is based upon preriously available testing procedures (74) as well as on everal newly developed tests which will be considered n detail. These tests measure fire and decomposition lazards-health hazards have not been considered.
Many regular commercial chemicals may be classified in a precise manner in accord with flammability hazard standards set up by such organizations as the Manufacturing Chemists’ Association, National Fire Protection Association, National Board of Fire Underwriters, and the Factory Mutual Engineering Division. Such classifications are based on flash points, ignition temperatures, and explosive or flammable limits of vapor. The Bureau of Explosives of the Association of American Railroads conducts tests for the Interstate Commerce Commission and, at present, classifies organic peroxides for transportation purposes. Procedures are used to evaluate the thermal stability and impact or shock sensitivity characteristics of the peroxides. Regulated materials are then classified for shipping under yellow label or red label in accordance with T. C. George’s Tariff No. 15 (7). None of the procedures previously mentioned allows a complete hazard evaluation and classification of organic peroxides. These compounds may possess the combination of thermal instability, sensitivity to shock and/or friction, as well as flammability. The hazard does not vary directly with the concentration of peroxide nor with active oxygen content in a formulation, nor does it
DEFINITIONS O F HAZARD CLASSES
Y
101. 5 6
NO. 182
DECEMBER 1 9 6 4
19
depend only on the type of peroxide. Storage, handling, and packaging conditions must therefore be given separate consideration for each formulation. A number of bulletins and papers have been published on the safety of organic peroxides. Most of these list properties or hazards connected with a few peroxides but have made no attempt to classify organic peroxides according to their safety characteristics. N.B.F.U. Research Report No. 11 (73), published in 1956, tabulated commercially available products and described some test procedures. Other papers have discussed the hazards of several peroxides in a general way (7, 2, 77) and some have made suggestions for storage, handling, and disposal (8, 70, 75). I n 1962 Siemens (77) evaluated peroxides on the basis of thermal and mechanical sensitivity, as well as explosiveness, and tabulated test data to compare fourteen organic peroxides. One of the tests described, the pressure vessel test, has now been modified and used in the present work. Guillet and Meyer (5) in their paper on “Determining Shock Sensitivity of Liquid Organic Peroxides” developed two methods of testing. They modified the standard drop weight impact tester to determine the amount of gas liberated by a decomposition due to shock. The other method involved subjecting the product to the shock of a blasting cap in an autoclave with a measurement of the pressure evolved. The authors estimated the sensitivity of a peroxide by determining the dilution required to make the peroxide insensitive to the maximum energy supplied to the sample by the test apparatus used. I t was concluded that peroxide decompositions are low order deflagrations rather than detonations. The temperatures (calculated from the instantaneous pressure rise and the pressures generated) were much lower than those expected from a detonation. Methods for safe handling and storage of organic peroxides in the laboratory were recently described (74). Safety testing procedures were covered and data tabulated for a number of solid liquid and paste products. Some physiological or health aspects such as effect on eyes and skin were also discussed. No attempt, however, was made to classify the products by degree of hazard.
mercial products, two new tests (discussed in detail in the experimental section of this article) were developed. The pressure vessel test (PVT), assesses the rate and amount of energy generated in a peroxide decomposition. The self-accelerating decomposition temperature (SADT) test evaluates the thermal stability of a peroxide in the largest commercial package used. From the various procedures available, we chose the following tests to obtain the necessary data for our study :
-To determine the potential rate and/or violence associated with a peroxide decomposition, we used the pressure vessel test, the lead pipe deformation test, and the self-accelerating decomposition test (evaluated for manner of decomposition), -To determine the potential ease of ignition and/or decomposition, we used the self-accelerating decomposition test (actual temperature), the impact shock sensitivity test, and two flammability tests. For liquids, flash point tests determined flammability;
RATING SYSTEM-RATE
PRESSURE VESSEL TEST
Hazard Class
1
Detonation Deflagration Fire Low fire/negligible
Ajerture Diameter at Rupture ( M m . ) 10 1.0 314.8 78,7 0,787 < O . 787
LPD T E S T
Fire
The present evaluation program was designed to provide, at its completion, a n over-all potential hazard classification system for organic peroxides. Peroxides, whether commercially available in quantity or in the research and development stage, were previously screened for hazard in a series of safety and stability tests utilizing rather limited quantities of material. These tests, described in our earlier article ( 7 4 , included burning rate, heat sensitivity (heating a t rate of 4 O C. per minute), impact shock sensitivity, flash point, thermal stability at various temperatures, and subjection to the detonation of a blasting cap in the lead pipe deformation test. Since the emphasis of the present study was on com-
AND/OR VIOLENCE
IV
Low fire/negligible
Examjle Picric acid: pipe is fragmented. Ammonium nitrate: pipe is severed with a noticeable flaring of the lead at point of severance. Benzoyl peroxide : pipe is bulged and ruptured but not severed. Deformation of the pipe is less than with benzoyl peroxide but greater than that shown with water . IVater: pipe is deformed with some lead scaling.
SADT TEST-KATE
Hazard Class Detonation
Deflagration Fire Low fire/negligible
1
Description Complete decomposition with considerable destructive force, smoke, and/or report. Sudden decomposition with generation of force and/or smoke and fumes. Rapid and vigorous decomposition and/or burning. Slow decomposition accompanied by mild gassing or bubbling.
for solids and pastes, rate of ignition and/or burning tests evaluated this hazard.
u
I t was difficult previously to compare the data expressing decomposition violence with that expressing ease of decomposition because of the lack of a suitable terminology. T o achieve this comparison, in which the results of each test had to be rated as to the degree or type of hazard, clearly descriptive terms were needed. A recent Government bulletin (4) proposed a classification of liquid propellants according to potential hazard, naming the classes Detonation Hazards, Deflagration Hazards, Fire Hazards, and Relatively Low Fire Hazards. For our purpose this classification system could be easily adapted to describe the potential hazard situation in relation to testing organic peroxides for rates and violence of decomposition. The same terms are also used, with slight modification, and defined to describe the five classes of hazard, forming our over-all classification of peroxides found in Table I. RATING SYSTEM-EASE OF I G N I T I O N AND/OR BURNING
SADT TEST-EASE
Hazard Class Maximum Intermediate Low Negligible
I
Self Accelerating Decomposition Temperature Under 80" F. 80-1 10' F. 110-150' F. Over 150' F.
Hazard Class
Degree of Sensitivity
Maximum Intermediate Low
Shock sensitive below 2 in. Shock sensitive 2-1 5 in. Shock sensitive 15-36 in., or under special conditions-e.g., when frozen or if diluent is lost Not sensitive at maximum height of tester (36 in.)
Negligible
Solids: The Bureau of Explosives tester uses an 8-pound weight. Liquids: Our mod@ed tester for liquids uses a 5-kilogram weight.
Hazard Class
Flash Point
Maximum Intermediate Low Negligible
Under 80' F. 80-140" F. 140-200 ' F. Over 200" F.
Hazard Class Maximum Intermediate Low Negligible
Dejnition Ignites immediately with vigorous burning. Ignites and burns rapidly. Ignites and burns mildly and slowly. Difficult to ignite.
Evaluation of the Potential Rate and/or Violence of Decomposition
A rating system for the variety of results obtained in this category was devised by arbitrarily defining, on the basis of the individual test data, the following hazard classes for each test procedure : Detonation; Deflagration; Fire ; and Low Fire/Negligible Low fire and negligible were combined because the nature of the test results made it difficult to clearly differentiate between them. Each of the three tests and the rating system used in summarizing the results in Table I11 are described below. Pressure Vessel Test (PVT). This test is described in the experimental section. The size of the aperture needed to vent the decomposition vapors and prevent the rupture of a standard pressure disk is a measure of the rate and violence of the decomposition. Lead Pipe Deformation Test (LPD). A 10-gram sample in a test tube which fits snugly in a lead pipe of standard dimensions (0.75-inch i.d., 0.310-inch wall, 7.0 inches long) is subjected to the detonation of a No. 6 EB-10 blasting cap (Hercules Powder Co.). The damage to the lead pipe is the basis of the LPD rating. It should be noted that the LPD classification was established in our previous paper (14) and to have reference standards, it was necessary to combine the present hazard classes as above.
Self-Accelerating Decomposition Temperature Test (SADT). See experimental section for description of this test. The manner of decomposition in this test is also considered and is a measure of violence. Evaluation of Potential Ease of Ignition and/or Decomposition
I n this case the rating system used in evaluating the violence potential category was not completely applicable because of the difference in the nature of the tests. It would not be proper to rate a peroxide as a "Detonation Hazard," for example, merely because it had a flash point under 80' F. For this reason, we chose to describe the degree of hazard associated with tests used in this category as : Maximum Hazard, Intermediate Hazard, Low Hazard, and Negligible Hazard. Using the above expressions, each degree of hazard was defined on the basis of the test data as shown below. The peroxide ratings were then collated in Table IV. SADT Test. This test uses the largest commercial package. The highest ambient temperature at which the material can be stored without a self-accelerating decomposition occurring is the point checked in this evaluation. Impact Shock Sensitivity Test. This test deals with small amounts of material but is indicative of the potential impact sensitivity hazard. The test equipment differs slightly for solids and liquids although both use the same principle of a known weight falling a measured distance and striking the sample (74). Flammability Tests. FLASH POINT (Micro Open Cup). The flash point of a liquid peroxide is useful but not of major significance because most chemical VOL. 5 6
NO. 1 2 D E C E M B E R 1 9 6 4
21
industries using organic peroxides handle many more flammable materials. It is, however, an indication of ease of ignition in case of a fire. A special Micro Open Cup (74) is used in carrying out this test because of the thermal decomposition characteristics of organic peroxides which differ from ordinary flammable liquids. RATEOF IGNITION AND/OR BURNING.For solid or paste peroxides the flash point is not applicable, so the rate of ignition and burning of these materials was used. Relative Hazard Classification of Organic Peroxides
Having set up a rating system for correlating the
TABLE
II.
RESULTS
results of individual tests, we defined hazard groupings for peroxides in the five classes shown. We have included an “Intermediate Fire” class. The ratings and test data for each peroxide as summarized in the tables (11-IV) were reviewed as a whole and the individual peroxides were placed in the appropriate class. Table I contains the final classification of the organic peroxides tested. I t should be noted that a peroxide need only have one of the various properties listed in defining the five classes of potential hazard. The most unfavorable or hazardous result governs a product’s placement.
OF PRESSURE VESSEL TEST
( 5 g-GRAM SAMPLE) ‘ypicc 4ssay
% Aromatic Diacyl Peroxides Benzoyl Benzoyl, redried Benzoyl, wet BenzoyI in tricresyl phosphate in silicone fluid fire retardant p-Chlorobenzoyl in dibutyl phthalate 2,4-Dichlorobenzoyl in dibutyl phthalate in silicone fluid Aliphatic Diacyl Peroxides Lauro yl Decanoyl Acetyl in dimethyl phthalate Propionyl in heptane in hydrocarbon solvent (higher boiling) Ketone Peroxides Bis( 1-hydroxycyclohexyl) Cyclohexanone in dibutyl phthalate powder in paste Peroxyesters &Butyl peroxyacetatt in benzene in mineral spirits &Butyl peroxyisobutyrate in benzene in mineral spirits t-Butyl peroxypivalate in mineral spirits in mineral spirits 22
98 99.4 70
Vent a( Rupture Mm .
Aperture Area, Sq. Mm.
14.5 18.4
174.7 266.4
...
...
Average Heating Time, Sec.
95 95 Iecomposes in stages
50 50 50
< 1 ( 1 < 1
< <
