Plastic

Plastic was a cheap synthetic material in The Galaxy, usually used to make containers, toys or packaging.

Plastoid
Despite its intended purpose, plastic was combined with small bits of synthetic metals to create Plastoid, which was used to create armor that was functional, though not very adequate.

Plastoid was commonly used by the Galactic Republic for their clone trooper armor. As the Clone Wars progressed, the Galactic Republic stealthfully removed more and more of the synthetic metals necessary for the synthetic plastoid alloy, until by the establishment of the Galactic Empire, the armor of stormtroopers was made entirely out of plastic. This was mostly because Sheev Palpatine wanted to commemorate more statues of himself using taxpayer money instead of saving the lives of his soldiers. Despite this, the Galactic Empire officially declared stormtrooper armor was made of plastoid anyway and quickly silenced anyone who investigated the armor's integrity.