GC value of the 130 °C POE samples obtained with GB/T29848-2018 standard tests after 5 h (left) and after 5 h with additional heating up and cooling down periods (right). Heating and cooling ramps are shown in Figure 8. The first case - an exact extraction time of 5 h - is likely where a laboratory has a lot of samples to process and wants to run the test continuously without cooling and heating the solvent between tests. The second case may occur when the laboratory is less busy or safety requirements prohibit sampling from the 140 °C hot reaction flask. The difference is about 8%, one sample almost reaching the 60% gel content recommended by the manufacturer.