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Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as autoacceleration , and can cause fires and explosions. Step-growth vs. chain-growth polymerization
Autoacceleration of the overall rate of a free-radical polymerization system has been noted in many bulk polymerization systems. The polymerization of methyl methacrylate, for example, deviates strongly from classical mechanism behavior around 20% conversion; in this region the conversion and molecular mass of the polymer produced increases rapidly.
Materials that may form explosive mixtures with water and are capable of detonation or explosive reaction in the presence of a strong initiating source. Materials may polymerize, decompose, self-react, or undergo other chemical change at normal temperature and pressure with moderate risk of explosion (e.g., ammonium nitrate). 2.
The polymerization reaction of alkenes occurs similarly to the reactions in metallocene catalysts: L n Ti–CH 2 −CHR–polymer + CH 2 =CHR → L n Ti–CH 2-CHR–CH 2 −CHR–polymer. The two chain termination reactions occur quite rarely in Ziegler–Natta catalysis and the formed polymers have a too high molecular weight to be of ...
The most common application of polyurethane is as solid foams, which requires the presence of a gas, or blowing agent, during the polymerization step. This is commonly achieved by adding small amounts of water, which reacts with isocyanates to form CO 2 gas and an amine, via an unstable carbamic acid group.
Polymerization reactions also have a higher rate of production of acid soluble oils, resulting in higher acid consumption. Temperature; Typically, alkylation is carried out in the neighborhood of 20 °C. Higher reaction temperatures dramatically favor polymerization reactions that will dilute the acid.
In polymer chemistry, polymerisation inhibitors (US: polymerization inhibitors) are chemical compounds added to monomers to prevent their self-polymerisation. Unsaturated monomers such as acrylates , vinyl chloride , butadiene and styrene require inhibitors for both processing and safe transport and storage.
Buchner's first synthesis of cycloheptatriene derivatives in 1885 used photolysis and thermal conditions to generate the carbene. A procedure for preparation of the hazardous starting material needed for carbene generation in the Buchner reaction, ethyl-diazoacetate, is available in Organic Syntheses. [12]