For the current week, the overall ratings of four chemicals stocks are worse, according to the Portfolio Graderdatabase. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, PolyOne Corporation (POL) falls to a D (“sell”), worse than last week’s grade of C (“hold”). 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 stock currently has a trailing PE Ratio of 43.50. For more information, get Portfolio Grader’s complete analysis of POL stock.

Marrone Bio Innovations, Inc.’s (MBII) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). The stock receives F’s in Earnings Momentum, Equity, Cash Flow and Sales Growth. To get an in-depth look at MBII, get Portfolio Grader’s complete analysis of MBII stock.

Kraton Performance Polymers, Inc. (KRA) earns an F this week, falling from last week’s grade of D. 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) experiences a ratings drop this week, going from last week’s C to a D. 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.