英语语法分析

It was found that its oxygen index, smoke density were directly proportional to content of carburizer whereas its initial expanding time was inversely proportional to content of carburizer.

研究结果表明，材料的氧指数、烟密度与炭化剂的用量成正比，而起始膨胀时间与炭化剂的用量成反比。以直接模压成型方法制得的材料膨胀性能较好。