You must use a mix, usually 50/50 with water (distilled preferably).
I know a guy that built a homebuilt airplane with a foam core cowling around a liquid cooled engine. He built it from a kit that was well engineered. He could not get the temperatures to come down into the acceptable ranges so he cut out huge sections of the cowling to get better air flow. After considerable work he discovered that one must use a mixture of water with the antifreeze. He ruined the cowling for nothing!
True story....airplane was built at the Winona, Ms. airport.