The effects of measuring technique and sample preparation on the breakdown strength of polyethylene

The effects of specimen thickness, testing conditions and preparation technique on the measured ramp-breakdown strength of 2 polyethylene systems have been investigated. The obtained data have been found to be highly reproducible, enabling results under different test conditions to be correlated with one another. In all cases, an increase in ramp rate results in an increase in the measured breakdown strength, as does a reduction in sample thickness. Irrespective of the test parameters, the short-term performance of a polyethylene blend containing a designed microstructure is always improved compared to that of the base low density polyethylene alone. Impulse testing leads to an identical conclusion. The effect of the blending method has been shown to have a negligible effect on the breakdown strength, despite consequent changes in nucleation density, implying that it is the local lamellar texture that is responsible for the enhanced properties of the blend.