Streamline Plastics » About Streamline Plastics About Streamline Plastics. The Streamline companies began in 1990 as Streamline Plastics, a family-owned corporation focused primarily on injection molding. As our client base expanded and needed more About Streamline Plastics. The Streamline companies began in 1990 as Streamline Plastics, a family-owned corporation focused primarily on injection molding. As our client base expanded and needed more …