Sodium bicarbonate, blowing agents

The efficiency of azodicarbonamide and sodium bicarbonate blowing agents for PE foams was considered (253). These systems, which generate GO2 gas, are more suitable for compression moulding of foams. Blends of the blowing agents have a reduced exotherm, so are more suitable for polymer systems that are temperature sensitive, such as ethylene copolymers. 

Dichlorotrifluoroethane blowing catalyst, PU foams N,N, N",N"-Pentamethyldiethylenetriamine blowing/nucleating agent, thermoplastics Sodium bicarbonate blow-molded bottles Hydroxypropylcellulose blow-molded parts Polypropylene... 

Chemical blowing agents undergo decomposition at the vulcanisation temperature to form a gaseous species such as nitrogen or carbon dioxide, e.g., azo compounds, nitroso compounds, sulphonyl hydrazide compounds, ammonium carbonate, ammonium bicarbonate and sodium bicarbonate. 

Whilst sodium bicarbonate is the primary blowing agent, it is common compounding practice to use it in conjunction with a proportion of a weak acid, such as stearic or oleic acid, whose function is to trigger the reaction and assist in the uniform decomposition of the bicarbonate. The higher than normal fatty acid level will also act as a process aid, facilitating the bubble expansion process. 

ABS foam compositions have been developed that contain about 10 parts of a foam modifier and 0.5-2.0 parts of a blowing agent. Sodium bicarbonate is a suitable blowing agent. The foaming modifier is preferably adapted to decrease the foam density and to increase the foam swell of the composition (82). In particular, the foam modifier consists of SAN. The ingredients are admixed and then extruded. Articles with a specific gravity of 0.3-0.47 gem-3 are obtained. 

The manufacture of sponge rubber products such as gaskets for heat exchangers is based on the inclusion in the compound of chemicals which cause gas formation during vulcanization and thereby produce the desired porosity. Sodium bicarbonate and ammonium bicarbonate are examples of popular blowing agents. 

As for decomposable matter, examples are sodium carbonate, ammonium carbonate, sodium nitrite, sodium sulfite, and sodium bicarbonate. Other well-known examples are di-N-nitrosopentamethyl-enetetramine, N,N-disubstituted 5-amino-l,2,3,4-thiatriazole, diesters of azodiformic acid, diazonium salts, sulfonhydrazides, and N-alkyl N-nitrosodiacetoneamine (7). The water produced during the exothermic resol condensation reaction is used as a blowing agent for producing high-density foamed composites. 

Endothermic and inorganic chemical blowing agents have included materials that degrade into carbon dioxide when heated, such as sodium bicarbonate. Sodium bicarbonate s low decomposition temperature (100°C-140°C) suits its use with POs, though it can decompose rapidly, forming open-cell stmctures. Other endothermic agents include citric acid, sodium borohydride, and polycarbonic... 

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