What are the differences in thermal expansion between filled and unfilled polyethylene?

Polyethylene, a widely used thermoplastic, exhibits distinct thermal expansion behaviors depending on whether it is filled with additives or remains in its pure, unfilled state. Unfilled polyethylene typically has a high coefficient of thermal expansion (CTE), ranging from 100-200 μm/m·°C, due to its semi-crystalline structure and weak intermolecular forces that allow significant molecular movement when heated. This substantial expansion can limit its applications in precision engineering.

In contrast, filled polyethylene incorporates materials like glass fibers, minerals, or carbon additives, which dramatically reduce its thermal expansion. These fillers restrict polymer chain mobility and provide dimensional stability, lowering the CTE to 20-50 μm/m·°C. The reduction depends on filler type, concentration, and orientation within the matrix. While filled polyethylene offers improved thermal stability and mechanical strength, it may sacrifice some flexibility and impact resistance.

The choice between filled and unfilled polyethylene involves balancing thermal performance with other material properties, making understanding these differences crucial for applications in automotive, construction, and packaging industries where temperature fluctuations are common.