Since polymerization and chemical reactions polymers are the same in some aspects, but they vary when it comes to reaction engineering.
According to the reactor are designed. Polymers undergo chemical reactions by providing active sites to the reactants to proceed to the polymerization process.
As we know, there are wide varieties of polymer, each of this type have different properties and characteristics based on this there are different reaction process involved depending on the type of polymer.
For example, in the case of polyesters, they are hydrolyzed readily; styrene polymers (foams which we use for cutlery) are reactive by nitration, sulfonation, and reduction to provide ion-exchange resins.
Here polymers act as reagents (these are substances which cause the reaction), there is leverage of polymers acting as reagents, it will help in separation of reagent from the reaction mixture, they are mutual inaccessible in case of cross-linking (a bond which links one polymer to another) and possibility that we can cut or shape the polymer to provide a special application or purpose (all the synthetic polymers like Teflon, HDPE).
Some of the major reactions are stated below.
The first major reaction is cross-linking, wherein difunctional monomers or monomers with two double bonds can be arbitrarily divided into 1,3-diene and divinyl compounds.
These can produce cross-links or branching during polymerization. The reactivity of double bonds can be controlled, so that one just enough so that it will not polymerize under conditions, but under certain conditions can lead vulcanization (post-cross-linking polymerization).
Vulcanization is the process that converts elastomers into cross-linked polymers.
Sulfur is the most commonly used, vulcanization agent. For example vulcanization of rubber helps in enhancing mechanical properties. As stated it is a post-cross-linking polymeric reaction.
Then comes the degradation reaction, degradation changes in properties or characteristics such as tensile strength, stiffness, colour or shape, etc.
There are types degradation reactions, photo-induced degradation in which polymers are degraded by photolysis ( UV rays, gamma rays, etc.) to give lower molecular weight molecules, thermal degradation, chain growth polymers are degraded by hemolysis (a process where nanopores are generated) at high temperatures to give gases, monomers, oils.
Ex: PVC. Biological degradation involves degradation by microorganisms;
it has applications in medicine, agriculture, and packaging.
Also, oxidative degradation which leads to hardening, discolouration and surface change.
For any question please comment below
Go to the next Chapter-5 Types of Polymerization Reactions