BLOWING AGENTSFunction: To produce cellular productsCellular products are a solid gas composition consisting of a continuous polymer phase & a gas phase continuous or discreteClosed cell: Individual cells enclosed by polymer. High degree of buoyancy. Good insulating properties (Thermal, Electrical, Mechanical, Sound )Open cell: Interconnected cells. Absorbency, Capillary actionMethods of Cellular product production:Whipping airDiffusion of gas under pressurePowdered dry iceChemical reactions during polymerization or crosslinkingVolatile liquidsLeaching out soluble additivesChemical Blowing Agents

BLOWING AGENTS

BLOWING AGENTS

BLOWING AGENTSChemical Blowing Agents: Additives that decompose at elevated temperatures liberating large volume of gasRelease gas at a controllable rate over suitable short defined temperature rangeEasily dispersibleNo corrosive or toxic decomposition productNo adverse effect on propertiesInorganic: Low cost, Poor storage stability, Difficult to disperse(NH4) HCO3 : Gas yield very high. No residueNH4HCO3 NH3 + CO2 + H2O NaHCO3: Low gas yield. Alkaline residue2NaHCO3 Na2CO3 + CO2 + H2ONaBH4: 2Component system. Buffered solution + Acidic activatorNaBH4 + 2H2O 4H2 + NaBO2

BLOWING AGENTSOrganic Blowing Agents: Release Nitrogen.Nitroso Compounds:DNPT: Widely used in Rubbers. Fishy smell

N,N Dimethyl N,N DinirosoterephthalimideLow decomposition temperature. Open cell

Azo Compounds:Azocarbonamide: Smell & discoloration Azobisisobutyronitrile:

Generates free radicals. Polymerization & grafting

BLOWING AGENTSSulfonylhydrazides:Low exotherm.Discolor under U.V.Benzene sulfonylhydrazide: Affected by Phthalate & Phosphate Plasticizers NN oxybis(Benzene sulfonylhydrazide: Low blowing power