What are the differences in environmental stress cracking resistance between plastics?

Environmental stress cracking (ESC) represents one of the most common failure modes in plastic components, occurring when tensile stress and chemical exposure combine to cause brittle cracking. The resistance to ESC varies dramatically across polymer families due to fundamental differences in molecular structure, crystallinity, and chemical composition.

High-density polyethylene (HDPE) demonstrates superior ESC resistance among thermoplastics, particularly in applications involving detergents or alcohols. Its semi-crystalline structure and non-polar nature provide inherent protection against aggressive chemicals. This makes HDPE ideal for chemical containers and piping systems. In contrast, amorphous plastics like polycarbonate (PC) exhibit significantly lower ESC resistance despite their high mechanical strength. PC is highly susceptible to ketones, esters, and even certain oils, leading to catastrophic failure under stress.

The ESC performance of acrylonitrile butadiene styrene (ABS) falls between these extremes, with resistance varying by rubber content and molecular weight. Plasticizers, fillers, and other additives further modify ESC behavior—while some enhance resistance, others may create weak interfaces that accelerate cracking.

Standardized testing methods like ASTM D1693 provide quantitative comparisons through bent strip tests in controlled environments. Manufacturers must consider these differences when selecting materials for applications involving chemical exposure, as ESC remains a leading cause of unexpected plastic component failures across automotive, medical, and construction industries.