Density of Polyethylene Crystals Grown From Solution.

Area of Science:

• Polymer Science
• Materials Science

Background:

• Marlex 50 polyethylene is a widely used polymer.
• Understanding crystal density is crucial for predicting material properties.

Purpose of the Study:

• To accurately measure the density of Marlex 50 polyethylene crystals.
• To investigate the discrepancy between measured and crystallographic densities.

Main Methods:

• Crystals were grown from a 0.75% solution in p-xylene at 70 °C.
• Density was determined using a pycnometric method.
• Measurement accuracy challenges were addressed.

Main Results:

• The measured density was approximately 0.98 g/cm³ at 30 °C.
• This value is significantly less than the theoretical crystallographic density of 1.00 g/cm³.
• A density deficiency was observed.

Conclusions:

• The pycnometric method yielded a density lower than the crystallographic value for Marlex 50 polyethylene.
• Several potential explanations for this density deficiency were proposed.
• Further research is needed to fully understand the observed phenomenon.