To Remove a Material from the Model
You can remove a material from the model in one of the following ways:
Expand the Materials node on the Model Tree, right-click the material, and click Delete.
Remove a material using the following steps:
1. Click File > Prepare > Model Properties. The Model Properties dialog box opens.
2. Click change in the Material line. The Materials dialog box opens.
3. In the Materials in Model list, right-click the material and click Delete.
4. Click OK. The Materials dialog box closes.
5. Click Close. The Model Properties dialog box closes.
* 
If a material is referenced by other entities, for example, in Creo Simulate, you must first remove the dependencies before deleting the material.
If you remove a material that was set as the master material, then PTC_SYSTEM_MTRL_PROPS is set as the master material. You cannot remove PTC_SYSTEM_MTRL_PROPS from a part.