Polymerization hazard

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May attack some forms of plastics Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent,- Polymerization Hazardous polymerization unlikely to occur except when in contact with alkali metals or metallo-organic compounds Inhibitor of Polymerization 10 -20 ppm tert-butylcatechol. 

Polymerization Hazardous polymerization may occur avoid high temperature storage and moisture. 

F/>110°C). Hygroscopic. May form imstable and explosive peroxides. A possible polymerization hazard. Contact with strong oxidizers may cause fire and explosions. Contact with mixture of acetic acid + dinitrogen trioxide may cause explosion. Incompatible with strong bases, chlorinated hydrocarbons, nitro compoimds. On small fires, use foam, dry chemical, water spray, or CO2 extinguishers. 

Precaution Flamm. dangerous fire and explosion risk can react vigorously with oxidizers may form peroxides which may initiate exothermic polymerization Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Storage Storage hazard Uses Monomerfor acrylic polymers amphoteric surfactants chemical intermediate leather finish resins textile and paper coatings plastic films oral pharmaceuticals vitamin Bi modifier for oils/alkyds in food-contact coatings... 

Health and Safety Factors. Because of their high vapor pressures (methyl vinyl ether is a gas at ambient conditions), the lower vinyl ethers represent a severe fire hazard and must be handled accordingly. Contact with acids can initiate violent polymerization and must be avoided. Although vinyl ethers form peroxides more slowly than saturated ethers, distillation residues must be handled with caution. 

Reactivity Acrolein is a highly reactive chemical, and contamination of all types must be avoided. Violent polymerization may occur by contamination with either alkaline materials or strong mineral acids. Contamination by low molecular weight amines and pyridines such as a-picoline is especially hazardous because there is an induction period that may conceal the onset of an incident and allow a contaminant to accumulate unnoticed. After the onset of polymeriza tion the temperature can rise precipitously within rninutes. 

Since the principal hazard of contamination of acrolein is base-catalyzed polymerization, a "buffer" solution to shortstop such a polymerization is often employed for emergency addition to a reacting tank. A typical composition of this solution is 78% acetic acid, 15% water, and 7% hydroquinone. The acetic acid is the primary active ingredient. Water is added to depress the freezing point and to increase the solubiUty of hydroquinone. Hydroquinone (HQ) prevents free-radical polymerization. Such polymerization is not expected to be a safety hazard, but there is no reason to exclude HQ from the formulation. Sodium acetate may be included as well to stop polymerization by very strong acids. There is, however, a temperature rise when it is added to acrolein due to catalysis of the acetic acid-acrolein addition reaction. 

The relatively low flash points of some acrylates create a fire hazard. Also, the ease of polymerization must be home in mind in ah. operations. The lower and upper explosive limits for methyl acrylate are 2.8 and 25 vol %, respectively. Corresponding limits for ethyl acrylate are 1.8 vol % and saturation, respectively. All possible sources of ignition of monomers must be eliininated. 

Red Phosphorus. This aHotropic form of phosphoms is relatively nontoxic and, unlike white phosphoms, is not spontaneously flammable. Red phosphoms is, however, easily ignited. It is a polymeric form of phosphoms having thermal stabiUty up to ca 450°C. In finely divided form it has been found to be a powerful flame-retardant additive (26,45—47). In Europe, it has found commercial use ia molded nylon electrical parts ia a coated and stabilized form. Handling hazards and color have deterred broad usage. The development of a series of masterbatches by Albright Wilson should facihtate further use. 

Copolymerization is effected by suspension or emulsion techniques under such conditions that tetrafluoroethylene, but not ethylene, may homopolymerize. Bulk polymerization is not commercially feasible, because of heat-transfer limitations and explosion hazard of the comonomer mixture. Polymerizations typically take place below 100°C and 5 MPa (50 atm). Initiators include peroxides, redox systems (10), free-radical sources (11), and ionizing radiation (12). 

Pure diketene is stable for several weeks if stored at or below 0°C in an aluminum or stainless steel container. Glass should be avoided because of its inherent basicity which favors slow polymerization. Above 15°C slow decomposition occurs and the color becomes progressively darker. Pressure buHd-up Upon prolonged exposure to heat is possible. Heating and contamination of the container, especiaHy by acids, bases, and water, should be avoided. Residual vapors in empty containers are hazardous and may explode on ignition. 

Polymerizations of methacrylic acid and derivatives are very energetic (MAA, 66.1 kj/mol MMA, 57.5 kJ/mol = 13.7 kcal/mol). The potential for the rapid evolution of heat and generation of pressure presents an explosion hazard if the materials are stored ia closed or poorly vented containers. 

Methanol is stable under normal storage conditions. Methanol is not subject to hazardous polymerization reactions, but can react violendy with strong oxidizing agents. The greatest hazard involved in handling methanol is the danger of fire or explosion. The NFPA classifies methanol as a serious fire hazard. 

Threshold limit values for the components of cemented carbides and tool steels are given in Table 14 (176). There is generally no fire or explosion hazard involved with tool steels, cemented carbides, or other tool materials. Fires can be handled as metal fires, eg, with Type D fire extinguishers. Most constituents of tool materials do not polymerize. 

Fire and uncontroUed polymerization are a concern in the handling of chloroprene monomer. The refined monomer is ordinarily stored refrigerated under nitrogen and inhibited. This is supported by routine monitoring for polymer formation and vessel temperature. Tanks and polymerization vessels are equipped for emergency inhibitor addition. Formalized process hazard studies, which look beyond the plant fence to potential for community involvement, are routine for most chemical processes. 

After polymerization, excess monomer is stripped and recycled. The residual monomer content of the stripped emulsion does not represent an acute hazard. Worker exposure to monomer is monitored, and sources of exposure identified and corrected. 

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

Because of analogy of radical formation by iron(II) ion from either peroxides or oxaziridines, the latter were proposed repeatedly as initiators of radical chains, e.g. in styrene polymerization and in treatment of unsaturated polyesters. Oxaziridines appear to be easier to prepare than peroxides and to be less hazardous in handling (76MI50801). 

Use of high or low temperature, high pressure, vacuum or possible hazardous reactions (polymerization, oxidation, halogenation, hydrogenation, alkylation, nitration, etc.)... 

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