Interfacial structure of all -polyethylene laminate using scanning thermal microscope and nano-Raman spectroscope

The interfacial structure of all-polyethylene laminate (linear low density polyethylene (LLDPE)/deuterated polyethylene (D-PE)) was investigated using different microprobe methods, scanning thermal microscopy (SThM), and confocal laser nano-Raman spectroscopy. By scanning the thermal probe under isothermal conditions over a cross section of the laminate film, a high-contrast image of apparent thermal conductivity at the interfacial region was obtained even for the flat height region observed using an atomic force micrograph. The apparent thermal conductivity and the Raman intensity gradually change across the tapered interfacial region between the two PEs. The interfacial thickness was estimated to be in the micrometer-order depending on the thermal treatment of the laminate film. Additionally, the peel strength of the LLDPE/D-PE laminate increased as the interfacial thickness increased. This suggests that both the LLDPE and D-PE molecular chains were entangled with each other, and/or both crystalline lamellae were in an interlocking state during thermal treatment.