As we continue down the list of the best-performing stocks in the materials sector for 2012, Motley Fool materials analyst Taylor Muckerman tells us which ones are ranked No. 8, No. 7, and No. 6, and really performed admirably for investors this year. He tells us about International Paper (IP 0.93%) and how a new focus on packaging is helping the company thrive. He also looks at two strong agriculturally focused companies, Monsanto (MON) and CF Industries (CF 0.04%), and how they are benefiting from a growing global middle class and a decreasing amount of arable land, which means farmers need higher yields from their crops.