Keyword: «degree of crystallinity»

This paper is proposed to take into account in the mathematical model of thermal process the heat of phase transformation when developing the technology of welding polymer pipes at ambient air temperatures below the normative values. The used function of the degree of crystallinity on temperature is determined according to DSC data. A formula is given for determining the effective heat capacity coefficient in the shock-capturing method for solving the heat conduction problem with a phase transition in the temperature range.

The article presents the results of a study of polyethylene samples exposed to natural climatic factors for 18 months by Raman spectroscopy. The spectra were obtained at different depths from the sample surface and it was shown that the stages of material degradation depending on the depth have different degrees. An estimate of the degree of degradation from depth is given, according to which the material undergoes structural changes most intensively at a distance of up to 40 µm from the surface. At depths greater 80–100 µm, structural changes in the material are not detected.