Abstract

Thermal stability and kinetics of thermolysis of postconsumer milk containers made of high-density polyethylene (PC-HDPE) and filament rods extruded from them (HDPE-F) were examined by thermogravimetric analysis (TGA) with six linear temperature programs under a stream of nitrogen. The total weightloss of each sample took place in a one-step decomposition to volatiles at the heating rates, β = 1, 10, 25, 50, 70, and 100 Kmin^-1. The values of initial decomposition temperature, the temperature at the maximum thermal degradation rate, and the maximum rate of decomposition were increased by increasing the heating rate as was the expectation. The isoconversional method was used to evaluate the fundamental kinetic parameters, the activation energy barrier (E_a), the Arrhenius pre-exponential factor (A), and the mechanism of the reaction, f(α). The values of E_a were independent of the model and heating rate, as was expected. However, the values of A depended on the model and the extent of reaction (α). The values of the E_a of PC-HDPE initiated at 171 kJ/mol at α = 0.05 and it increased to 207 kJ/mole at α = 0.95. The values of E_a of the HDPE-F rod were relatively constant for all α values, being 227 ± 3 kJ/mol. It was justified by the absence of easily volatilized substances in the HDPE-F. Knowledge of the thermal stability and decomposition kinetics of the starting materials (PC-HDPE) and the product (HDPE-F) is important in the context of thermochemical conversion processes aimed at the use of PC-HDPE as raw materials for recycling, upcycling, and down-cycling for objects used under room conditions.

摘要

由高密度聚乙烯 (PC-HDPE) 和从中挤出的长丝棒 (HDPE-F) 制成的消费后牛奶容器的热稳定性和热解动力学通过热重分析 (TGA) 在氮气流下使用六个线性温度程序进行检查. 在加热速率 β = 1、10、25、50、70 和 100 Kmin ^-1下，每个样品的总重量损失发生在一步分解为挥发物的过程中。初始分解温度、最大热降解速率的温度和最大分解速率的值随着加热速率的增加而增加，这与预期一致。等转化法用于评估基本动力学参数，活化能垒（E _a)、Arrhenius 指前因子 ( A ) 和反应机理f (α)。正如预期的那样， E _a的值与模型和加热速率无关。然而，A的值取决于模型和反应程度 (α)。PC-HDPE 的E _a值在 α = 0.05 时起始值为 171 kJ/mol，在 α = 0.95 时增加到 207 kJ/mol。E _a的值对于所有 α 值，HDPE-F 棒的 α 值相对恒定，为 227 ± 3 kJ/mol。HDPE-F 中不存在易挥发的物质，这是合理的。在旨在将 PC-HDPE 作为原材料用于回收、升级再造、以及在室内条件下使用的物体的降级循环。