A polymer is a molecule composed of many repeating units. Covalent bonds typically connect these units. Polymers are found in both natural and synthetic materials. Examples of natural polymers include DNA, RNA, and proteins.
Synthetic polymers include plastics, rubber, and synthetic fibers. Polymers are classified according to their structure. The three main types of polymer structures are linear, branched, and network. Linear polymers are composed of repeating units arranged in a straight chain. Branched polymers have repeating units that are arranged in a branching structure.
Network polymers have repeating units that are cross-linked, forming a three-dimensional network. Its structure determines the properties of a polymer. Linear polymers tend to be strong and tough, while branched polymers are softer and more flexible.
Network polymers are usually rigid. A variety of methods can produce polymers. The most common method is polymerization, a chemical reaction that links together small molecules to form a polymer chain. Polymerization can be carried out using different types of monomers or small molecules. In plastics, anionic polymerization and condensation polymerization are the most prevalent and can be seen in all the petroleum-based plastics
For example, the polymerization of ethylene gas produces polymer polyethylene. There are two main types of polymerization reactions: addition polymerization and condensation polymerization. Addition polymerization reactions involve the addition of monomers to a growing polymer chain.
Condensation polymerization reactions involve the linking of two monomers through the removal of a small molecule, such as water.
A variety of methods can degrade polymers. The breaking of bonds causes thermal degradation in the polymer chain due to exposure to high temperatures. Chemical degradation is caused by the attack of chemicals on the bonds in the polymer chain.
The breaking of bonds causes physical degradation in the polymer chain due to physical forces, such as shearing or stretching. Polymer degradation is an important process in the recycling of plastics and other polymeric materials.
The recycling of polymers can be achieved by several methods, such as mechanical recycling, chemical recycling, and energy recovery. Mechanical recycling is breaking down a polymer material into smaller pieces that can be used to create new products.
This process is typically done by shredding or grinding the polymer material.
Chemical recycling is breaking down a polymer material into its monomers that can be used to create new products. This process is typically done by treating the polymer material with chemicals that break the bonds between the monomers. Energy recovery is converting the energy in a polymer material into a usable form, such as electricity or heat. This process is typically done by burning the polymer material.