Effects of Liquid Paraffin on Dynamic Mechanical Properties of Linear High-Density Polyethylene
Asae Ito, Kaori Hioki, Koichi Kono, Yusuke Hiejima, Koh‐hei Nitta
Abstract
We found that the dynamic mechanical spectra of linear high-density polyethylene (HDPE) can be controlled by swelling using liquid paraffin (LP) at 100 and 110 °C. The relaxation strength of α relaxation observed above 50 °C decreased with an increase in swelling time. Two novel peaks appeared between γ and α relaxations, denoted as β1 and β2 on the lower temperature side, respectively. These peaks are absent in pristine HDPE and are associated with the immersion of LP molecules in the amorphous phase. β1 appeared at approximately −50 °C and was almost independent of frequency; it is believed to be responsible for the glass transition of LP domains. Meanwhile, β2 appeared at approximately −20 °C, similar to the β-relaxation temperature observed in linear low-density polyethylene (PE) and ultrahigh molecular weight PE. β2 was responsible for the activation of molecular motion in the rigid amorphous chains, such as taut tie-chains in the interlamellar regions, in which the addition of LP expanded the amorphous layers and caused surface melting of the crystalline lamellae.