Blender 3D: Noob to Pro/Every Material Known to Man/Hard Plastic
Plastic is Easy
Yes, this page won't actually tell you what you specifically need for plastic, because it's a very simple material. People think too much, so "I" am here to tell you that sometimes the solution is the simplest one.
Hard Plastic is made by taking the standard material (the material created when you hit the "Add New" button) and taking the "Hard" Value under the "Shaders" tab and turning it up. You can also turn up the "Spec" Value, also located under the "Shaders" tab.
Nothing to it. Like every other material you can add scratches by making very thin normal maps and very lightly applying them, and maybe make the plastic reflective by turning on a very shallow "RayMir" property.