Which polymerization process has the highest reaction rate?
Which polymerization process has the highest reaction rate?
4 Methyl-Methacrylate Bulk Polymerization The polymerization is highly exothermic and exhibits a strong acceleration in polymerization rate due to gel-effect (e.g., the termination rate constant decreases with conversion).
What is the rate determining step in free-radical polymerization?
Formation ofinitiating radicals is the rate-determining step in the initiation reaction. The process can result, as shown in Table 2.1, from cleavage of compounds, like peroxides, or from other sources. Many reactions lead to formations of free radicals.
How do you calculate the rate of polymerization?
Divide the molecular weight of the polymer by the molecular weight of the monomer unit to calculate the degree of polymerization. If the molecular mass of tetrafluoroethylene is 120,000, its degree of polymerization is 120,000 / 100 = 1,200.
What will increase the rate of polymerization?
The growth rate increases linearly with the concentration of monomer, and as the square root of the initiator concentration. Suppose the following data were obtained for a radical polymerization conducted at various starting concentrations of monomer.
What is the result of polymerization?
Polymerization, any process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer. The monomer molecules may be all alike, or they may represent two, three, or more different compounds.
Why is degree of polymerization important?
Correlation with physical properties Polymers with identical composition but different molecular weights may exhibit different physical properties. In general, increasing degree of polymerization correlates with higher melting temperature and higher mechanical strength.
Does temperature affect the rate of polymerization?
The temperature affects both the rate of free radical formation and the thermody- namic properties of the polymerization system. It is also shown that higher levels of initiator at a particular temperature actually produced larger particles.
What is kinetic chain length and degree of polymerization?
Kinetic chain length is defined as the average number of monomers that react with an active center such as a radical from initiation to termination. In fact the kinetic chain length is one factor which influences the average degree of polymerization, but there are other factors as described below.
What are the kinetics of free radical polymerization?
Now that we have a working understanding of the reactions and processes that can happen during free radical polymerization, we can begin to discuss the polymerization kinetics for free radical polymerization. We start from the very beginning and define the rate of polymerization:
How to calculate the length of a radical polymerization?
Given a radical polymerization with [M] 0 = 4.5 M and [I] 0 = 1.25 mM, compare chain length in the following situations: b) a non-living polymerization with f = 0.5; kp = kt = 0.003 s -1; kd = 0.0001 s -1.
How does termination occur in radical polymerization process?
Termination can occur by several different mechanisms. If longer chains are desired, the initiator concentration should be kept low; otherwise, many shorter chains will result. Combination of two active chain ends: one or both of the following processes may occur.
What is the rate of initiation in polymerization?
We can update our description of the rate of initiation: Propagation involves the transfer of the radical from one monomer to another monomer, or to polymer. We are using up lots of monomer in this step.