Final answer:
The commonly used insulating materials in cryotainers are fiberglass and foam, which are effective due to their structure containing air pockets that hinder thermal conductivity.
Step-by-step explanation:
The two commonly used insulating materials used in the annular space of a cryotainer are fiberglass and foam.
Insulation is a critical factor in the design of cryotainers, which are containers used to store materials at very low temperatures. These containers need to minimize heat transfer to maintain the cold temperature required to preserve their contents. Fiberglass and polystyrene foam are excellent choices for insulation because they contain many small pockets of air, which take advantage of air's poor thermal conductivity.
Both these materials are commonly utilized due to their insulating properties as reflected in scientific observations. For instance, fiberglass is also mentioned alongside wool and goosedown feathers as a good insulator. Polystyrene foam, a type of plastic that is comprised of 92.3% carbon and 7.7% hydrogen, is also recognized as a poor thermal conductor, making it an effective insulator.