This week, 4 Chemicals stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Celanese Corporation Class A (CE) earns a B this week, jumping up from last week’s grade of C. Celanese Corporation Class A is a global integrated producer of chemicals and advanced materials. The company also gets A’s in earnings surprise and return on equity. For more information, get Portfolio Grader’s complete analysis of CE stock.

Kraton Performance Polymers, Inc. (KRA) shows solid improvement this week. The company’s rating rises from a B to a A. Kraton Performance Polymers, Inc. produces engineered polymers and styrenic block copolymers. The company also gets A’s in sales growth, operating margin growth, earnings revisions, earnings surprise, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of KRA stock.

This week, Westlake Chemical Partners LP’s (WLKP) ratings are up from a C last week to a B. The company also gets A’s in earnings growth, earnings momentum, and return on equity. For more information, get Portfolio Grader’s complete analysis of WLKP stock.

Flexible Solutions International Inc. (FSI) gets a higher grade this week, advancing from a B last week to a A. Flexible Solutions International Inc. develops and markets chemicals and chemical dispensers, which slow down the evaporation of water. The company also gets A’s in operating margin growth, earnings growth, earnings revisions, earnings momentum, and free cash flow. For more information, get Portfolio Grader’s complete analysis of FSI 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.