Plastics can be mixed with other materials to create a material with properties that are more than the sum of their parts.
An extreme, if simple, example is Marcel Wanders ‘Sparkling’ chair (1). Ordinary polyethylene terephthalate (PET), as used in water bottles, has been combined with pressurised air to create from these two unstructural materials a structure that can hold the weight of a person.
Plastics can be mixed with antimicrobials before extrusion, as was the case with the X-Static sock (2), to create a fabric that inhibits growth of bacteria such as cause athletes foot. Similarly additives can enable plastic to change colour under certain conditions as in the case of the Tommee Tippee weaning set spoon (3), which turns from red to yellow if the food is too hot.