What is gel effect in polymerization?
The gel effect is a major problem in a free radical polymerization. It consists of a fast and sudden increase of the overall rate of the process and therefore also of the viscosity of the medium and it occurs at intermediate or high degrees of conversion depending on the operating conditions.
Which are the characteristic features of the gel effect auto acceleration effect in free radical polymerization?
1. What is the characteristic feature of the gel effect in radical polymerization? Explanation: Gel or auto-acceleration effect is accompanied by increasing trend in reaction rate and molecular weight of polymer product, which results into the formation of highly viscous mass.
What is auto acceleration what causes this effect and how do you minimize this effect?
Autoacceleration (Gel Effect, Trommsdorff–Norrish Effect) is a dangerous reaction behavior that can occur in free radical polymerization systems. This decrease in termination rate, kt, is caused by the raised viscosity of the polymerization region when the concentration of previously formed polymer molecules increases.
What is trommsdorff Norrish effect?
Autoacceleration (gel effect, Trommsdorff–Norrish effect) is a dangerous reaction behavior that can occur in free-radical polymerization systems. It is due to the localized increases in viscosity of the polymerizing system that slow termination reactions.
What is gel effect in communication?
The effect of nasal or inhaled oral hydration on the larynx is greater when we combine the breathing in of moisture with the production of gentle sound. This combination optimizes water penetration into the tissues. The moisturizing effect can last between 30 minutes and several hours.
What is the trommsdorff Norrish effect?
Which catalyst is used in coordination polymerization?
Ziegler-Natta
HDPE is produced by coordination polymerisation using a catalyst, usually Ziegler-Natta (ZN).
What is degree of polymerization in chemistry?
The degree of polymerization (DP or Xn) is defined as the number of monomer units in the polymer. It is calculated as the ratio of molecular weight of a polymer and molecular weight of the repeat unit. Number average DP and weight average DP are the two main types used for measuring the DP.
What are the advantages of emulsion polymerization?
The advantages of emulsion polymerization are that its use permits a rapid polymerization to a high molecular weight with narrow molecule weight distribution, the viscosity is typically lower than other methods, heat is relatively easy to remove from the reactor with water as the continuous phase and suitable for the …
How do you stop auto acceleration?
To avoid the occurrence of thermal runaway due to autoacceleration, suspension polymerization techniques are employed to make polymers such as polystyrene. The droplets dispersed in the water are small reaction vessels, but the heat capacity of the water lowers the temperature rise, thus moderating the reaction.