This week, the ratings of 4 Chemicals stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Celanese Corporation Class A (CE) earns a D this week, moving down from last week’s grade of C. Celanese Corporation Class A is a global integrated producer of chemicals and advanced materials. For more information, get Portfolio Grader’s complete analysis of CE stock.

This is a rough week for PolyOne Corporation (POL). The company’s rating falls to D from the previous week’s C. PolyOne Corporation is an international polymer services company with operations in North America, Europe, Asia, Australia, and South America. For more information, get Portfolio Grader’s complete analysis of POL stock.

AgroFresh Solutions, Inc. (AGFS) slips from a D to a F this week. The company also gets F’s in operating margin growth and earnings revisions. For more information, get Portfolio Grader’s complete analysis of AGFS stock.

This week, BioAmber, Inc. (BIOA) drops from a C to a D rating. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of BIOA 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.