Environmental stress cracking resistance (ESCR) is an important property required for plastics to last. It is one of the common causes of unexpected brittle failure in thermoplastics. Environmental stress cracking may account for around 15-30% of all plastic component failures in service. Therefore, performing ESCR testing on plastics is what manufacturers need to do.
What is Stress Cracking?
The definition of stress cracking is defined in many standards. It is described as an internal or external crack in plastics, caused by stresses that are less than their short-term mechanical effectiveness.
This type of cracking typically consists of brittle cracking with little ductility or pull of plastic material from adjacent surface failures. Slow growth of cracks is another term used to explain stress cracking.
The preferred form of slow crack growth is ESC or Environmental Stress Cracking. The following are some examples involving cracking of stress specimens, usually in the presence of active wet agents such as soaps, surfactants, alcohols, etc. These aerosols do not attack the polymer directly, nor do they affect the specimen in any way other than the appearance of small cracks.
In the absence of surfactant, under the same conditions, these breaks do not occur within any reasonable period of time. Cracks often start as tiny defects and spread to nearby areas of the polymer structure. This ability of a plastic coupon or polymer to resist cracking or environmental stress cracking is commonly referred to as Environmental Stress Crack Resistance (ESCR). Different polymers show different degrees of ESCR. Some types of HDPE have good resistance to environmental stress cracking , while some types are less elastic.
Why is economic, social and cultural rights testing important?
Stress cracking can lead to failure or decomposition of plastic materials. Plastic needs to withstand the entire life cycle of a product before it can fail. For polyethylene, this can range from months for juice bottles to decades for natural gas lines and car fuel tanks. Therefore, before starting production, it is very important to measure the ESCR and other related properties of polyethylene for safe and reliable production.
How is Environmental Stress Cracking Resistance Measured?
As material quality has improved over the past few years, the term SCG or Slow Crack Growth has been widely introduced in the testing world to identify various ESCR methods. To measure the effect, the samples were kept at different temperatures. The higher the set temperature, the faster the crack will be generated. Follow this test procedure to expedite ESCR testing on specimens .
