Melting behavior of thin polyethylene films

Melting behavior in thin films of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) was studied by local thermal analysis (µTA). Even in the films thinner than 100 nm, the melting temperature ( T _m ) was successfully observed by µTA. For LLDPE, T _m decreased as the thickness became thinner than 150 nm. For HDPE, T _m increased with decreasing thickness. Polarized infrared spectroscopy revealed that an edge-on lamellar structure formed in both cases, meaning that the crystallite orientation may not be a reason why the thickness dependence of T _m was not the same for both resins. A possible explanation is that for LLDPE the segmental mobility in the amorphous region predominates with decreasing thickness, and for HDPE the chain orientation in the region predominates with decreasing thickness.