Reviewed by Anurag Mishra (Sr. Technical Consultant)
Environmental stress crack resistance is an essential characteristic of materials, particularly polymers, that defines their strength under pressure and contact with extreme conditions. The issue emerges when materials form fractures due to chemical contact, resulting in early degradation.
The solution involves improving polymer compositions, integrating enhancers, and refining manufacturers' methods. In this article, there are several stress testing techniques, applications, types, and factors impacting stress cracking we will understand to maintain the durability of plastics.
Environmental Stress Crack Resistance refers to the failure of polymer material caused by surface-initiated microcracks or failures. It is the development of fractures in a material due to relatively low-tensile stress combined with environmental factors.
Environmental stress cracking resistance is measured as the number of hours required for 50% of tested specimens to exhibit stress-induced cracking. Therefore, testing plastics for ESCR is essential for manufacturers.
One common application of ESCR is found in high-density polyethylene (HDPE) chemical containers. HDPE containers must withstand stress and chemical exposure to avoid cracking, which might result in product failure or leakage.
Plastics are extensively employed in industries because they are lightweight yet strong. Their resistance to corrosion and chemical attack makes them the first choice over other materials. Nevertheless, if they are exposed to stress and environmental conditions for a long period, cracks can form, weakening their durability.
To maintain reliability, plastic products are tested by manufacturers using ESCR. It identifies how resistant a material is to stress cracking and makes sure that the final product is durable, efficient, and safe for extended use.
The ESCR test is an established procedure used to assess the durability of plastics to stress cracking. For plastic bottles, the assessment (test) usually includes exerting pressure while subjecting the material to a defined chemical condition. The ESCR test procedure involves:
A notch is made on the surface of the plastic specimen, and a pulling force is exerted. The polymer is then subjected to a designated chemical such as detergent or alcohol, for a specific duration to check if the crack spreads.
The polymer specimens are subjected to continuous pressure while undergoing chemical exposure. The advancement of fractures is monitored over time to assess the material’s durability.
The specimen is subjected to an actual chemical or an environmental challenge such as UV radiation, or temperature extremes. To replicate real conditions in which the polymers will be utilized.
The ESCR test methods for plastic bottles involve applying mechanical stress while subjecting it to certain environmental factors. This assesses the bottle’s capacity to withstand cracking under stress. Commonly known methods include the notched tensile test, stretched cracking, and environmental exposure test in practical situations.
Environment stress crack resistance is a crucial property of plastic materials as it determines their ability to withstand fractures when exposed to external factors like chemicals, temperature variations, or mechanical stress over time. Here are some key aspects highlighting the importance of ESCR in plastics:
Product durability: A high ESCR value helps plastic products stay strong against different climatic conditions, extending their life and upgrading performance such as pipes, car accessories, and containers.
Quality Control: Testing for ESCR helps manufacturers identify problems in plastic materials and adjust production to maintain reliability and quality.
Cost Efficiency: Choosing plastics with the best ESCR can reduce early breakdowns, minimizing the need for related expenses and substitutions.
Environmental stress cracking is caused due to elevated temperatures, repeated stress concentrations, different levels, and material degradation. The factors which cause environmental stress are described below:
Higher temperatures boost environmental stress cracking by enhancing molecular movement within the polymer, weakening its structure, and increasing its vulnerability to fracture.
Repeated stress concentration results in environmental stress cracking by forming concentrated weak points in the material. Over time, repeated stress leads to the expansion of micro-fractures, particularly in the presence of chemicals.
Material degradation compromises the integrity of the polymer’s molecular framework over time due to factors such as oxidation, Ultraviolet exposure, or chemical exposure. This lowers its capacity to resist pressure by increasing its susceptibility to fracture development in harsh environments.
Various applications ensure durability and accuracy in the testing of environmental stress crack resistance (ESCR). The application includes Plastics, Automotive Industries, medicines, and chemicals, which are mentioned below:
ESCR is widely applied in the polymer and plastics industries to assess the durability of these materials under environmental pressure. Plastics and polymers are commonly applied in various applications such as packaging, automotive, construction, and medical devices.
The automotive industry is another field that uses ESCR testing. Parts like fuel tanks, pipes, and hoses encounter different chemicals over their lifespan. ESCR testing assesses the capability of these parts to resist contact with fuels, oils, and other chemicals, guaranteeing their strength and safety.
In the medical industry, ESCR testing guarantees that materials in medical devices are secure and dependable. Medical devices frequently come into contact with strong chemicals, like disinfectants and cleaning agents, which may lead to deterioration.
Assessing materials’ durability against chemical exposure with ESCR testing guarantees their accuracy and safety.
The chemicals and petrochemicals are also completely dependable on ESCR testing. This testing assesses the durability of materials against chemical contact, which is essential for uses such as storage, and chemical processing. ESCR testing assists manufacturers in selecting the most suitable materials for specific applications, guaranteeing their durability under demanding conditions.
Environment stress crack resistance is a crucial property containing polymers and plastics. After knowing about the ESCR testing methods, applications, and causes is clear that manufacturers will only select the materials that offer the best reliability and durability by eliminating the risks of failure and expanding materials' life duration in a real-world environment.
+91 9313 140 140 
info@testronixinstruments.com
