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 stock’s trailing PE Ratio is 26.40. 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 gets 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.

This week, Kraton Performance Polymers, Inc.’s (KRA) rating worsens to an F from the company’s D rating a week ago. 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) gets weaker ratings this week as last week’s C drops 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.