Classes of Incompatible Chemicals

Certain hazardous chemicals when stored or mixed together react violently. These chemical substances are unsuitable for mixing and are incompatible. During storage, classes of incompatible chemicals should be segregated from each other according to hazard class. In chemical laboratories, more often than not chemicals are stored alphabetically. This has led to the occurrence of several chemical disasters and explosions. It is important that incompatible chemical substances be handled, stored, and disposed of with care and caution and that no contact is made from one chemical to the other. The following are a few selected incompatible chemical substances. Chemicals in coiumn A should not come in contact with chemicals in coiumn B ... 

Materials that become more hazardous when contacted with water comprise another important class of incompatible materials. For example, carbonyl sulphide (COS) and calcium sulphide (CaS) both release toxic H2S on contact with water. Dry powders of sodium or potassium cyanide release toxic HCN in the presence of moisture. Care must be taken to prevent such materials from coming into contact with water during processing and storage. The 1985 Bhopal accident was started by a runaway reaction involving a water-sensitive chemical. 

Alternatively (or initially) the mixture is treated as a whole and tested in its crude state. The advantage of this strategy includes the relevancy of the tested sample to its environmental counterpart, decreased potential for artefact formation, and inclusion of combined effects of chemicals in the mixture. Moreover if the mixture is representative of others in its class (e.g., diesel emissions from different sources would share certain characteristics), it may be possible to extrapolate results across samples. This method also circumvents the labor-intensive process of individual testing of multiple chemicals. But sometimes a complex mixture is too cytotoxic to be tested directly in a bioassay. Furthermore, it may be incompatible with the test system because of the physical matrix. Other disadvantages include the inability to specify the constituent of the mixture responsible for the toxicity, as well as potential masking effects (e.g., the masking of mutagenicity by cytotoxicity). 

The last contribution in the prevailing volume deals with the application of a relatively new class of materials based on the addition of (electron-beam) activated polytetrafhioroethylene (PTFE) powder in rubber matrixes for preparing PTFE-based elastomeric composites. Besides other properties, the remarkably lower friction coefficient of PTFE enables its utilization for tribological applications. However, PTFE in rubbers has not been fully explored mainly due to its inherent chemical inertness and incompatibility. The present work signifies the electron modification of PTFE powder to improve its compatibility with rubber matrixes, the state of the art regarding its application in rubbers, and the preparation of PTFE-based elastomeric composites for several tribological applications. 

It was determined that Adoarwax 225, one of the bisamide waxes, is chemically incompatible with RDX. This class of material was dropped from the program. Whether the incompatibility is typical of this family of waxes was not determined. Work on the acrylic latexes was discontinued when it was found that the result-... 

Recently, a versatile class of poly(ethylene propylene)/poly(ethylene oxide) block copolymer micelles were introduced they were stable due to a combination of high block incompatibility, kinetically frozen core, and high interfacial tension between core and solvent [53, 58]. Moreover, by using a co-solvent of varying composition, the aggregation number was controlled and soft spheres from star-like to micelle-like could be obtained. Another way is core stabilization via chemical crosslinking, say by UV radiation [59-64]. 

BARIUM SULFIDE (21109-95-5) BaS Flammable solid. Oxidizes in dry air. Contact with acid, acid fumes, moisture, steam, or moist air causes decomposition with the formation of toxic and flammable hydrogen sulfide gas. Evolved gas can form explosive mixtures with air and may cause spontaneous ignition or explosion. Violent reaction with strong oxidizers, calcium chlorate calcium nitrate chlorine dioxide phosphorus(V) oxide strontium chlorate strontium nitrate. Incompatible with lead dioxide, potassium chlorate, potassium nitrite may explode at elevated temperatures. On small fires, use smothering quantities of dry chemical powder, dry clay, dry groimd limestone (CaCOj), dry soda ash,dry sand or approved Class D extinguishers, do not use water, foam, or hydrous agents. 

One of the most common groups of chemicals that are violently incompatible are acids and bases. While grouped together in the same DOT hazard class of corrosives, these materials are generally not stored together because of the potential dangers. 

Class of Chemicals Recommended Storage Method Examples Incompatibilities... 

Azo BCs are one fascinating class of soft materials, showing a rich variety of microphase-separated nanostructures in films because the strongly bonded azo segments and the non-azo blocks are thermodynamically incompatible. As shown in Fig. 12.1, the microphase-separated morphologies can be controlled to be spheres, cylinders, or lamellae, depending on the length, chemical nature, architecture, and number of repeated units in each block (e.g., Thomas and Lescanec, 1994). 

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