Thermoplastics are divided into two material classes (amorphous and semi-crystalline). Their classification is determined by both their transition temperatures and their structure in different states, which works great for molded silicone parts.
Plastics are either organic or semi-organic materials that have (as their main attribute) a very large molecular weight. These very large molecules, or macromolecules, give them their distinct properties and material behavior, when compared to other materials used in manufacturing or found in nature.
Plastics can be divided into uncross-linked thermoplastics and cross-linked thermosets. The first have intermolecular bonds between the molecule chains, but can move freely relative to their neighbors. They can be melted and solidified multiple times. In contrast, thermosets have “bridges,” or covalent, bonds interconnecting the polymer molecules. Once the material is solidified by chemical curing, it cannot be melted again.