IMPROVEMENT OF THE TEST PROCEDURE OF ANENVIRONMENTAL STRESS CRACKING RESISTANCETEST OF HIGH-DENSITY POLYETHYLENE

摘要

The environmental stress cracking resistance (ESCR)testing is aligned to the polyolefin's business thatuses this test. This test is necessary to understandthe resistance of polyolefins against common envi-ronmental stress cracking (ESC) agents such as soapy water,silicon oil, and insect repellent. The main need of improvingthe ESCR test is to get improved data that are used to avoidunexpected long-term failures of polyolefin products. Forsemicrystalline polymers such as polyethylene (PE), it isknown that ESCR is less severe than in amorphous polymers.However, exposing PE to stress crack agents results in unex-pected brittle fracture. ~(1,2)Crazes are accompanied by this frac-ture, and this cannot be determined by conventionalmechanical properties of the polymer but rather by the ESCRtests. But recently, the practical relationship between ESCRand some physical properties, such as the strain hardeningmodulus,~3creep deceleration factor,~4tie chain concentration,and permeability,~5 is proposed for the qualitative evaluationof ESCR properties of polymers. There are some known majorenvironmental factors governing ESCR such as the exposuretime of the stress cracking agent, exposure temperature, con-centration of the stress cracking agent, and level of strain onor in the polymer.~6