Which method of polymerisation out of bulk,solution,suspension,emulsion is used to prepare elastomer?
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METHODS OF POLYMERIZATION
Polymerization reaction may take place in any of the three states of matter- solid, liquid, gas. The solid state reactions are usually slow, they are not considered practical for this reason. The gas-phase reactions do take place but normally they require maintenance of high temperatures, a condition in which almost all high molecular weight polymers become unstable. Hence almost all commercial process of polymerization are liquid phase reactions.
LIQUID-PHASE REACTIONS:
→
Homogenous type
Bulk Polymerization/Mass Polymerization
Solution Polymerization
→
Heterogeneous type
Emulsion Polymerization
Suspension Polymerization/Pearl/Bead Polymerization
The homogenous or heterogeneous terms refers only to initial conditions of the system and are not to the subsequent conditions. For example, Polymerization of vinyl chloride by mass polymerization method is considered a homogenous type of reaction, because initially the system is homogenous. But the polymer being incompatible to the monomer phase, the system subsequently becomes heterogeneous. Hence the concept of homogeneity or heterogeneity is based on only the initial conditions of the system.
MASS POLYMERIZATION
In this type of polymerization the monomer is taken in liquid form. The initiators, chain transfer agent- used to control the molecular weight are dissolved in monomer. Now the system becomes homogenous. The reaction mass is heated or exposed to a radiation source for the purpose of initiating the polymerization reaction and is kept under agitation for proper heat and mass transfer. As the polymerization proceeds the viscosity of the medium increases and mixing becomes difficult leading to products with very broad molecular weight distribution. The reaction is purely exothermic. Batch reactors are used for polymerization
Polymerization reaction may take place in any of the three states of matter- solid, liquid, gas. The solid state reactions are usually slow, they are not considered practical for this reason. The gas-phase reactions do take place but normally they require maintenance of high temperatures, a condition in which almost all high molecular weight polymers become unstable. Hence almost all commercial process of polymerization are liquid phase reactions.
LIQUID-PHASE REACTIONS:
→
Homogenous type
Bulk Polymerization/Mass Polymerization
Solution Polymerization
→
Heterogeneous type
Emulsion Polymerization
Suspension Polymerization/Pearl/Bead Polymerization
The homogenous or heterogeneous terms refers only to initial conditions of the system and are not to the subsequent conditions. For example, Polymerization of vinyl chloride by mass polymerization method is considered a homogenous type of reaction, because initially the system is homogenous. But the polymer being incompatible to the monomer phase, the system subsequently becomes heterogeneous. Hence the concept of homogeneity or heterogeneity is based on only the initial conditions of the system.
MASS POLYMERIZATION
In this type of polymerization the monomer is taken in liquid form. The initiators, chain transfer agent- used to control the molecular weight are dissolved in monomer. Now the system becomes homogenous. The reaction mass is heated or exposed to a radiation source for the purpose of initiating the polymerization reaction and is kept under agitation for proper heat and mass transfer. As the polymerization proceeds the viscosity of the medium increases and mixing becomes difficult leading to products with very broad molecular weight distribution. The reaction is purely exothermic. Batch reactors are used for polymerization
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