Self-reactive

Va2o-64, Self-Reactive Solid Type C, Temperature Controlled (2,2 -a2odi(iso-butyronitrile)). 

Va2o-88, Self-Reactive Solid Type D (l,l -a2odi(hexahydroben2onitrile)). 

Chemical Hazards. Chemical manufacturers and employees contend with various ha2ards inherent ia productioa of evea commonplace materials. For example, some catalysts used ia the manufacture of polyethylene (see Olefin polymers) ignite when exposed to air or explode if allowed to become too warm the basic ingredient ia fluorocarboa polymers, eg, Tefloa (see Fluorine compounds, organic), can become violently self-reactive if overheated or contaminated with caustic substances (45,46) one of the raw materials for the manufacture of acryflc fibers (see Fibers, acrylic) is the highly toxic hydrogen cyanide (see Cyanides). 

Self-reactivity can be defined as the potential for a material to decompose or undergo energetic changes. Some of the methods for characterizing selfreactivity hazards are listed in Table A.3. 

Table A.3 Methods for Conducting Self-Reactivity Experimental Screening...

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Avoid contamination with combustible materials, various inorganic and organic acids, alkalies, alcohols, amines, easily oxidizable materials such as ethers, or materials used as accelerators in polymerizations reactions Stability During Transport Extremely explosion-sensitive to shock, heat and friction. Self-reactive Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent inhibitor of Polymerization Not pertinent. 

All of tlie recoimnended heat flax equations in API 520 and NFPA Codes tliat are used to design relief valve assmne tliat tlie liquids are not self-reactive or subject to runaway reaction. If tliis situation arises, it is necessary to include tlie heat of reaction and tlie rate of tlie reaction into account in sizing the relief device. 

Good quality steel is used and electrozinc is preferred for washing machines. Steel is pretreated with iron phosphate for economy electrozinc with a fine crystal zinc phosphate. No primer is normally used 25-40/im of finish is applied direct to metal. The required properties are best obtained with a thermosetting acrylic or polyester/melamine-formaldehyde finish. Self-reactive acrylics are usually preferred these resins contain about 15 Vo 7V-butoxymethyl acrylamide (CH2=CH —CO —NH —CHj—O —C4H,) monomer and cure in a manner similar to butylated melamine-formaldehyde resins. Resistance or anti-corrosive properties may be upgraded by the inclusion of small amounts of epoxy resin. Application is usually by electrostatic spray application from disc or bell. Shapes are complex enough to require convected hot-air curing. Schedules of 20 min at 150-175°C are... 

CH3C = CH, mw 40.07, colorl liquified gas bp —23.1°, fr p —101.5° flammable, dangerous fire and expl risk. It is self-reactive, and can decomp explosively at 4.5 to 5.6 atms press (Ref 2). An expin occurred at Dow s Freeport, Texas plant in 1960 while workers were loading a small tank of methyl acetylene. Following this expln, a 2000 gal tank blew up and burned for hours. The cause of the blasts were not detd (Ref 1)... 

This example of step-growth polymerization has two monomers that can react with each other but not with themselves. It has only one dimer that can be self-reactive. This pattern continues indefinitely with two trimers, one self-reactive tetramer, and so on. Molecules with an odd number of mer units will... 

Breakdown of tolerance mechanisms. There are at least two mechanisms for maintaining unresponsiveness to self The first is by specific deletion of self-reactive clones and the second by suppression. A failure of either of these two may result in an autoimmune disease. In normal, healthy individuals, antigen-binding, self-reactive B cells and the resultant low litres of autoantibodies are not uncommon. The origin of the self-reactive B cells is not clear, but there are four ways in which they may become activated. 

The therapeutic goal in autoimmune diseases such as RA is to control disease, to establish remission, and eventually to cure. In theory, this goal can be achieved using either Ag-specific approaches, for example, elimination of self-reactive T cells (assuming that a finite number of key Ags can be identified as the target of the autoimmune process in RA), or the non-Ag-specific approaches, for example, blockade of cytokines as in the case of TNF-a neutralization. Currently, only the latter types of approaches have yielded clinical benefit, and it is in this category that approaches to block chemokines or receptors may be included. Despite their appeal in terms of effectiveness, non-Ag-specific approaches carry a higher risk of immunosuppression and opportunistic infections (48). 

Kronenberg, M. and Rudensky, A., Regulation of immunity by self-reactive T cells, Nature, 435, 598, 2005. 

Explosibility—detonation of pure substance not likely, deflagration cannot be excluded Thermal Stability/Runaway Potential—high energy compound, additional testing required Reactivity—self-reactive substance... 

Fisher, H. G. and D. D. Goetz, "Determination of Self-Accelerating Decomposition Temperatures for Self-Reactive Substances," /. Loss Prev. Process Ind., 6, No. 3,183-194 (1993). 

Self-reactive substances (polymerizing, decomposing, rearranging)... 

Decomposing materials are sometimes referred to as unstable, and generally they have a positive heat of formation such that energy will be released when the decomposition reaction occurs. Self-reactive materials can often be recognized by the presence of certain chemical structures that tend to confer reactivity. These include... 

The first four questions address substances that are reactive with air, water, or ordinary combustibles—materials that are almost certain to be in close proximity to the reactive substances. The next question addresses self-reactive materials. This is followed by a final question combined with a series of steps for addressing chemical incompatibility. 

Organic peroxides, included in the same general DOT/UN Hazard Class (Class 5) as oxidizers, are considered here to be self-reactive materials, so are addressed with Question 11 below. 

Five general categories of what can go wrong with self-reactive materials are ... 

Concentration of self-reactive material, resulting in an uncontrolled increase in reaction rate. 

Initiation of uncontrolled self-reactions at a given facility can occur in storage or during handling, mixing, physical processing or chemical reactions. A few of the many possible causes of uncontrolled reactions associated with self-reactive materials include the following ... 

Hot work in area or on equipment containing self-reactive material... 

If the answer to Question 11 is YES, then you should make use of the information in Chapter 4, because a chemical reactivity hazard is present. The essential practices presented in Chapter 4 should be sufficient to manage this type of chemical reactivity hazard, excluding considerations for commercial explosives, which are also self-reactive materials. 

If you are certain that NO self-reactive substances are present, then proceed to the next question (Question 12). If you are uncertain as to whether a material is self-reactive, a chemist or other expert should be consulted. Annex E to NFPA 704 (2001) gives a method for calculating an "instantaneous power density," defined as the product of the enthalpy... 

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