Thermal Degradation of HDPE in a Batch Pressure Reactor: Reaction Time and Mechanical Stirring Effect

Abstract

The effect of reaction time and mechanical stirring on thermal degradation of high density polyethylene(HDPE) was studied at 350 • C under nitrogen atomosphere in a batch pressure reactor. Changes in molecular weight(MW), molecular weight distribution (MWD), and crystalline behaviors of the degraded products were investigated by gel chromatography (GPC) and differential scanning calorimetry (DSC). It was found that MWD curves all shifted toward lower molecular weight with increasing reaction time, with both the extent of the movement and its Mw showing a rapid initial drop and then leveling off. In a short period of reaction time, the MW, MWD and crystalline behaviors of the degraded products were affected notably by the mechanical stirring. The Mw of the degraded products without stirring was lower than that of products with stirring in the same time, which should be related to the large difference of temperature distributions in the reactor. When the reaction time reached 4 h, the Mw of the degraded products had dropped to about 5 × 10 3 g/mol from about 3 × 10 5 g/mol for the original Mw, and the product did not show the melting and crystallization behaviors of high density polyethylene again.

Application of Mechanical Heat Treatment for the Recovery of Plastics as Energy Resource

“…As shown in Fig. 3, there is no significant dry weight change before and after cooking process in a steaming condition of 100, 150 and 180 o C. As HDPE has a melting point of 130-140 o C and a degradation point of 350-380 o C [7], the results indicate that the melting of HDPE at 150 and 180 o C has negligible effect on dry weight reduction. …”

Effective dissolution of UHMWPE in HDPE improved by high temperature melting and subsequent shear

“…Also, Fu et al also confirmed that UHMWPE had very little weight loss at 280°C for a duration of 24 h under nitrogen atmosphere. Moreover, according to our previous work , HDPE did not begin the chain scission of the carbon‐carbon bonds under nitrogen until the temperature was above 300°C. Thus, we adopted 280°C in this work to investigate the effect of HTM on the blending of UHMWPE with HDPE.…”