"main material" is correct and usable in written English.
For example, "The main material used to build the bridge was concrete."
"Time is my main material," she explains.
Here the main material is metal signs.
The main material for her jewelry is Plexiglas, and her palette is Crayola rich and bright.
Much of the electricity for making a solar panel goes into producing the main material, polysilicon.
Satire of TV seems to be the show's main material, regardless of who the emergency colleague is.
For a given size of nuclear blast, plutonium weapons are smaller and lighter than those made of uranium, the other main material used as fuel for nuclear warheads.
The show's name, "Groundwork," is apt because Mr. Toia's main material and inspiration of late is mushrooms, especially bracket mushrooms with gills and a lot of surface area.
This new separation technique enables Desso to separate the yarn and other fibres from the carpet backing, thereby producing two main material streams that can then be recycled.
After some glassy "mistuned" skirls in the viola all hands make a pass at retuning before returning to the main material.
Solyndra and Evergreen in particular suffered because they pursued unusual technologies whose competitiveness depended on their using less polysilicon, the main material for solar panels.
Until now, China has tended to pursue retaliatory trade actions against industrial products, including imports of polycrystalline silicon, the main material for solar panels.
