generally require the use of high temperature and stirring in order to destroy the crystals. On cooling, the polymer will recrystallize and precipitate from the solution. For this reason, high temperature is required throughout the entire analysis to ensure that the samples remain in solution during the experiment. Thus, it is necessary that the GPC systemisequipped withacolumn heater inorder tokeep the polymer in solution and to obtain reliable and reproducible results. In general, all different sections of the equipment have to be kept at high temperature to avoid the precipitation of the polymer and the blockage of the tubing due to an increase of the pressure of the system. The equipment
for HT-GPC is specially made to stand high temperatures. HT-GPC allows the measurement of average MWs and MWDs of polymers that will not dissolve in GPC solvents at conventional GPC temperatures. For analysis at high temperature, it is necessary to prepare standards at the same experimental conditions as used to prepare the normal samples; the standards commonly used for high temperatures are polystyrene and polybutadiene, among others.