Why ESCR is Important
Because stress cracking results in the breakdown or failure of a plastic material, a plastic part needs to
endure its entire designed life before it fails. For polyethylene, this may range from several months for a
milk or juice bottle to several decades for an automotive fuel tank or natural gas pipeline.
In the late 1940s, Western Electric was encountering occasional cracking in the low-density polyethylene
used to jacket wire cables. Bell Labs was asked to investigate the cracking and they found the cause to
be lubricating soaps used during installation. Through this research, the Bell Labs Bent Strip ESCR test
was born and became the first ESCR test.
How ESCR or Resistance to Slow Crack Growth is Measured
As materials have improved over the years, the term “slow crack growth (SCG) resistance” has been
used to identify all the various ESCR test methods described below. The most widely used and oldest
SCG test is the Bent Strip ESCR test. Due to limitations of the Bent Strip ESCR method, several
alternative ESCR tests have been developed for use in the United States and Europe. These include
PENT and NCTL in the United States and FNCT in Europe. All are explained as follows.
ASTM D1693 – Bent Strip ESCR Test
Developed by Bell Labs in the late 1940s, this is one of the original and best-known ESCR tests.
Why ESCR is Important
Because stress cracking results in the breakdown or failure of a plastic material, a plastic part needs to
endure its entire designed life before it fails. For polyethylene, this may range from several months for a
milk or juice bottle to several decades for an automotive fuel tank or natural gas pipeline.
In the late 1940s, Western Electric was encountering occasional cracking in the low-density polyethylene
used to jacket wire cables. Bell Labs was asked to investigate the cracking and they found the cause to
be lubricating soaps used during installation. Through this research, the Bell Labs Bent Strip ESCR test
was born and became the first ESCR test.
How ESCR or Resistance to Slow Crack Growth is Measured
As materials have improved over the years, the term “slow crack growth (SCG) resistance” has been
used to identify all the various ESCR test methods described below. The most widely used and oldest
SCG test is the Bent Strip ESCR test. Due to limitations of the Bent Strip ESCR method, several
alternative ESCR tests have been developed for use in the United States and Europe. These include
PENT and NCTL in the United States and FNCT in Europe. All are explained as follows.
ASTM D1693 – Bent Strip ESCR Test
Developed by Bell Labs in the late 1940s, this is one of the original and best-known ESCR tests.
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