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

LSB Industries, Inc. (LXU) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). LSB Industries manufactures and sells chemical products for the mining, agricultural, and industrial markets. In Portfolio Grader’s specific subcategories of Earnings Growth, Earnings Momentum, Earnings Revisions, Cash Flow and Sales Growth, LXU also gets F’s. For more information, get Portfolio Grader’s complete analysis of LXU stock.

Marrone Bio Innovations, Inc. (MBII) earns an F this week, falling from last week’s grade of D. 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.

The rating of Braskem S.A. Sponsored ADR Pfd Class A (BAK) declines this week from a D to an F. Braskem produces and sells basic petrochemicals and thermoplastic resins in Brazil and internationally. The stock gets F’s in Earnings Growth, Earnings Revisions, Cash Flow and Sales Growth. For more information, get Portfolio Grader’s complete analysis of BAK stock.

Praxair, Inc.’s (PX) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Praxair supplies gas to industries primarily located in North and South America. To get an in-depth look at PX, get Portfolio Grader’s complete analysis of PX 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.