Accelerated test for evaluating slow crack growth of polyethylene copolymers in igepal and air

The time for brittle failure by slow crack growth for 22 polyethylene copolymers was measured in Igepal and air. The notched tensile tests were conducted in Igepal and air at 50°C and 4.2 MPa and in air at 80°C and 2.4 MPa. For failure times less than 10 3 min, the difference between the Igepal and air environments was not measurable. As the failure time increased beyond 10 3 min, the ratio of failure in air compared to that in Igepal increased so that for the very highest failure times of 5 × 10 5 to 108 min in air, the failure time in Igepal was reduced by 25—50 times. The correlation between the Igepal and air tests was generally good with respect to all types of polyethylene. However, a separation of the polyethylenes with respect to their comonomer, butene, hexene, or octene improved the correlation. The resistance to slow crack growth of all the current commercial polyethylene copolymers can be assessed by a notched tensile test in Igepal in about a week or less.