The grades of three chemicals stocks are better this week, according to the Portfolio Grader database. Every one of these stocks has an “A” (“strong buy”) or “B” overall (“buy”) rating.

Axiall Corporation (AXLL) is progressing from last week’s rating of B (“buy”) as the company improves to an A (“strong buy”) this week. Axiall Corporation operates as an integrated chemicals and building products company in North America and Asia. In Portfolio Grader’s specific subcategories of Earnings Revisions, Earnings Surprise and Equity, AXLL also gets A’s. The stock price has risen 10.2% over the past month, better than the 1.7% decrease the S&P 500 has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of AXLL stock.

This is a strong week for Stepan Company (SCL). The company’s rating climbs to A from the previous week’s B. Stepan Company produces specialty and intermediate chemicals that are sold to other manufacturers. For more information, get Portfolio Grader’s complete analysis of SCL stock.

Senomyx, Inc.’s (SNMX) grade is moving up to a B (“buy”) this week from last week’s C (“hold”). Senomyx discovers new proprietary flavor and fragrance molecules for use in a wide range of consumer products. For more information, get Portfolio Grader’s complete analysis of SNMX stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.