The overall ratings of four chemicals stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

PolyOne Corporation’s (POL) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. PolyOne is an international polymer services company with operations in North America, Europe, Asia, Australia, and South America. In Portfolio Grader’s specific subcategories of Earnings Growth, Earnings Momentum and Sales Growth, POL also gets an F. The trailing PE Ratio for the stock is 44.80. For more information, get Portfolio Grader’s complete analysis of POL stock.

Marrone Bio Innovations, Inc. (MBII) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). In Earnings Momentum, Equity, Cash Flow and Sales Growth the stock gets F’s. Shares of the stock are being traded at a very rapid pace, up 1477% from the week prior. To get an in-depth look at MBII, get Portfolio Grader’s complete analysis of MBII stock.

Kraton Performance Polymers, Inc. (KRA) experiences a ratings drop this week, going from last week’s D to an F. Kraton Performance Polymers produces engineered polymers and styrenic block copolymers. The stock gets F’s in Earnings Momentum and Earnings Surprise. For more information, get Portfolio Grader’s complete analysis of KRA stock.

Huntsman Corporation (HUN) earns a D this week, falling from last week’s grade of C. Huntsman manufactures differentiated and commodity chemical products. The stock gets F’s in Earnings Momentum, Earnings Revisions and Earnings Surprise. To get an in-depth look at HUN, get Portfolio Grader’s complete analysis of HUN 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.