Low Stress Brittle Fractures in Polymers: Progress Report, August 1, 1987--August 1, 1988

摘要

The results of the effect of molecular parameters show: (1) that crack resistance varies as (M/sub w/--M sub 0 ) for PE where M/sub w/ is weight average molecular weight and M sub 0 --20,000; (2) butyl branches are more effective than ethyl; (3) crack resistance increases with branch density; (4) there is an unknown factor that increases crack resistance even if molecular weight and branch density is the same. Fundamental parameters such as the stress distribution on the boundary of the process zone can now be measured. The activation energy of slow crack growth for different types of polyethylene range from 83-115 KJ/mol. The basic research data is being applied toward the prediction of the life-time of the 200,000 miles of polyethylene gas pipe that is now in service in the United States. (ERA citation 13:046963)