In the petrochemical industries, a variety of low density polyethylene (LDPE) grades are produced from a single reactor line with changes in process conditions and/or materials. Herein the microstructure parameters, for example, monomer conversion, average molecular weight ($\overline{Mn}$), long chain branches (LCB) and short chain branches (SCB), are calculated for various process conditions in the polymerization process such as chain transfer agent (CTA) type and concentration, CTA feed position, initiator feed position, temperature profile, and residence time in the reactor, all based on industry data. Our results showed the CTA with a high rate constant makes three times more LCB but decreases the SCB by 13% relative to the CTA with a low rate constant. Also, for the same CTA type, $\overline{Mn}$ decreased if the CTA concentration was increased. Injection of initiators at the beginning of the process had no significant effect on the SCB but increased the LCB by 54%. The new equations presented here to predict the microstructure of LDPE produced in tubular reactors resulted in good agreement with reported experimental values. The equations advantage is that the industrial data of the LDPE polymerization can be analyzed with high accuracy and speed to obtain the LDPE microstructure.

在石油化学工业中，随着工艺条件和/或材料的变化，从单个反应器生产线可生产各种低密度聚乙烯（LDPE）级。此处的微观结构参数，例如单体转化率，平均分子量（$\overline{\mathrm{中号}ñ}$），长链支链（LCB）和短链支链（SCB）是针对聚合过程中的各种过程条件计算的，例如链转移剂（CTA）的类型和浓度，CTA进料位置，引发剂进料位置，温度分布和反应堆中的停留时间全部基于行业数据。我们的结果表明，相对于低速率常数的CTA，高速率常数的CTA可使LCB增大三倍，但SCB降低13％。另外，对于相同的CTA类型，$\overline{\mathrm{中号}ñ}$如果增加CTA浓度，则降低。在过程开始时注入引发剂对SCB无明显影响，但LCB增加了54％。此处提出的用于预测管式反应器生产的LDPE微观结构的新方程式与报告的实验值具有很好的一致性。该方程式的优点是可以高精度和快速地分析LDPE聚合的工业数据以获得LDPE微观结构。