TY - JOUR
T1 - Temperature-modulated differential scanning calorimetric measurements on pre-melting behavior of nascent ultrahigh molar mass polyethylene
AU - Hoehne, G.W.H.
AU - Kurelec, L.
AU - Rastogi, S.
AU - Lemstra, P.J.
PY - 2003
Y1 - 2003
N2 - Temperature-modulated differential scanning calorimetric (TMDSC) measurements on nascent ultrahigh molecular mass polyethylene (UHMMPE) in scanning as well as quasi-isothermal mode are presented. From these measurements different processes, which contribute to the modulated heat flow in the pre-melting region, both exothermic and endothermic in character, can be separated. One of them only occur on the first heating of the nascent material. Analysis of quasi-isothermal measurements, performed between 90 and 130 °C, show that there are two slow (exponential) relaxation processes with time constants of 2–5 and 10–100 min, respectively. One, exothermic in character, seems to be connected with irreversible structural changes (crystal thickening and ordering). The low activation energy (ca 40 kJ mol-1) points to a chain diffusion process rather than melting and crystallization. The other process (activation energy 60 kJ mol-1) seems to be endothermic. In the melting region, a slow (>100 min) 3rd relaxation process with high activation energy (300 kJ mol-1) can be separated.
AB - Temperature-modulated differential scanning calorimetric (TMDSC) measurements on nascent ultrahigh molecular mass polyethylene (UHMMPE) in scanning as well as quasi-isothermal mode are presented. From these measurements different processes, which contribute to the modulated heat flow in the pre-melting region, both exothermic and endothermic in character, can be separated. One of them only occur on the first heating of the nascent material. Analysis of quasi-isothermal measurements, performed between 90 and 130 °C, show that there are two slow (exponential) relaxation processes with time constants of 2–5 and 10–100 min, respectively. One, exothermic in character, seems to be connected with irreversible structural changes (crystal thickening and ordering). The low activation energy (ca 40 kJ mol-1) points to a chain diffusion process rather than melting and crystallization. The other process (activation energy 60 kJ mol-1) seems to be endothermic. In the melting region, a slow (>100 min) 3rd relaxation process with high activation energy (300 kJ mol-1) can be separated.
U2 - 10.1016/S0040-6031(02)00528-2
DO - 10.1016/S0040-6031(02)00528-2
M3 - Article
VL - 396
SP - 97
EP - 108
JO - Thermochimica Acta
JF - Thermochimica Acta
SN - 0040-6031
IS - 1-2
ER -