Which type of initiator is needed for emulsion polymerization?
Initiators. Both thermal and redox generation of free radicals have been used in emulsion polymerization. Persulfate salts are commonly used in both initiation modes. The persulfate ion readily breaks up into sulfate radical ions above about 50 °C, providing a thermal source of initiation.
Which compound is used in chain transfer agent in polymerization?
Common chain transfer agents include thiols, especially dodecyl mercaptan (DDM), and halocarbons such as carbon tetrachloride.
In which polymerization initiator and CTA are dissolved in the monomer?
suspension polymerization
In suspension polymerization, monomer droplets with dissolved initiator are commonly dispersed in water. As the polymerization progresses, the droplets are transformed into sticky, viscous monomer–polymer particles that finally become rigid, spherical polymer particles of size 50–500 μm.
What is a chain transfer agent?
Chain transfer agents, also called modifiers or regulators, have at least one weak chemical bond. These compounds react with the free-radical site of a growing polymer chain and interrupt chain growth.
Which monomer can undergo chain Polymmerisation?
Many common polymers can be obtained by chain polymerization such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinyl acetate (PVA).
Is the commonly used initiator in polymerization techniques?
The most widely used initiators produce free radicals (reactive atoms or groups of atoms that contain odd numbers of electrons); examples include peroxides and aliphatic azo compounds used to polymerize vinyl chloride, methyl methacrylate, and other monomers.
Which monomer can undergo chain polymerization?
What is the role of initiator in chain growth polymerization?
Usually an initiator compound reacts with the monomer to start the reaction, and the mechanism of chain polymerization consists of three phases, called initiation, propagation, and termination.
What are the chain transfer agents in emulsion polymerization of styrene?
The effect of chain transfer agents on the nucleation and growth of polymer particles in the emulsion polymerization of styrene were examined extensively. The chain transfer agents used are carbon tetrachloride, carbon tetrabromide, and four primary mercaptans (C 2, n -C 4, n -C 7, and n -C 12 ).
How does the amount of chain transfer agent affect the polymerization rate?
It is shown that with an increase in the amount of chain transfer agents charged the rate of polymerization per particle decreases progressively. The number of polymer particles formed, on the other hand, increases initially then decreases.
What is a chain transfer agent used for?
Chain transfer agents are used to control the molecular weights of polymers like butadiene copolymers, which are subsequently isolated and processed. G. Moad, S.H. Thang, in Polymer Science: A Comprehensive Reference, 2012
Can TTCA surface-active RAFT agent be used to control polymerization of 275?
A surface-active RAFT agent, the sodium salt of 2- (dodecylthiocarbonothioylthio)-2-methylpropanoic acid) (TTCA; Figure 23 ( a )), was further tested 275 as TTCA is a widely employed TTC, known for controlling efficiently the polymerization of a large variety of monosubstituted ethylenic monomers 276 in homogeneous conditions.