Manifestation of the monoclinic phase in IR spectra of ultrahigh-molecular-weight polyethylene

Abstract

A new band situated in the vicinity of 1056 cm−1 has been observed in the IR spectrum of UHMW PE. This band appears during compaction of the reactor powder, pressing of pellets, and drawing of the resulting films at room temperature. The intensity of the band increases with the time of staying under pressure in proportion to logt with a simultaneous reduction in the intensity of absorption bands corresponding to the orthorhombic phase of PE. Upon staying of the samples at room temperature, the intensity of this band decreases for a long time with a concomitant increase in the intensity of the bands due to the orthorhombic phase of PE. An increase in temperature accelerates this process, and annealing at 100°C for 30 min brings about disappearance of the 1056-cm−1 band and cessation of an increase in the intensity of absorption bands corresponding to the orthorhombic phase of PE. On the basis of the above data, it is inferred that the band at 1056 cm−1 may be attributed to the monoclinic phase of PE.