A linear Union Carbide PE (UC) has been analyzed by nonstandard calorimetry with a common DSC calorimeter and a Setaram C80 calorimeter. Nonstandard calorimetry entails using a low rate of heating (0.5-1 K/min), a small mass (0.5-1.5 mg), and an open cell (O-cell) instead of the standard C-cell. Events in O-cells overlap less and occur with a faster kinetics than in C-cells. PE crystals are nascent, solution-grown (S-grown), press-grown (P-grown), and strained by extrusion. In Part A, the traces show that the phase-changes in the melt, previously observed in a C80 calorimeter (slow T-ramp) and characterized by Delta H-network, can be observed with a common DSC in nonstandard conditions. In Part B, the difference between the C- and O-cells and the changes in the main peak enthalpy (Delta H-ortho) are of interest. The main result is that, in O-cells, the value of Delta H-otho around T-ortho, exceeds unambiguously in certain conditions Delta H-ortho found for perfect orthorhombic crystals. The main endotherm contains then another contribution, namely Delta H-network. Crystal reorganization during the slow T-ramp is followed in the C- and O-cells on S-grown crystals. In O-cells, lamellar thickening observed in the slow-ramp is more extensive. The ease of phase-change depends on the sample history. It is as follows: strained-part extruded > nascent > S-grown > P-grown. Co-operative chain motions are more hindered in the standard C-cells than in the O-cells. In Part C, lower values of m succeed in bringing phase-changes in P-grown (O-cells) samples. The origin of the events is discussed: three processes are thought to contribute to the phase-changes namely, melting of strained short-range order, activation of vibrations in the CH2 groups, and fast decay of chain orientation which occurs simultaneously with melting. (c) 2007 Wiley Periodicals, Inc.