Thermal Degradation Of High Density Polyethylene Research Articles

Catalytic pyrolysis of petroleum-based and biodegradable plastic waste to obtain high-value chemicals

The petroleum-based plastics, high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), and the biodegradable plastic, polylactide (PLA) were processed by thermal and catalytic pyrolysis to investigate their suitability as feedstock for chemical recycling. The influence of pyrolysis temperature (400–600 °C) and catalyst (zeolite, spent FCC, and MgO catalyst) on the pyrolysis liquid composition and yield was studied. The studied petroleum-based plastics had similar decomposition temperature ranges but produced their highest pyrolysis yields at different temperatures. Pyrolysis liquids from thermal degradation of HDPE and LDPE consisted high yield of waxes but those of PP and PLA consisted of both waxes and liquid oil. Catalysts affected not only the pyrolysis yield, but also the proportions of liquid oil and wax in pyrolysis liquids. Alkenes, alkanes, and aromatics were the main compounds in the pyrolysis liquids. Spent FCC catalyst reduced the production of waxes and increased the production of gasoline-range hydrocarbons and aromatics. MgO catalyst led to high coke formation from polyolefins and PLA. Lactic acid, lactide and propanoic acid were examples of valuable chemicals recovered from the pyrolysis of PLA. Lactide was the main product (up to 79%) of catalytic pyrolysis with zeolite at 400 °C. Spent FCC catalyst produced mostly propanoic acid at 400 °C but at 600 °C, L-lactic acid became the most abundant compound.

Study on Thermal Degradation and Kinetic of Microencapsulated Red Phosphorus (MRP)/High Density Polyethylene (HDPE) Composite

Thermal degradation of the composite constituted by high density polyethylene (HDPE) and microencapsulated red phosphorus (MRP) were studied using thermogravimetric (TG) data obtained at different heating rates. The kinetic models and parameters of the thermal degradation of MRP/HDPE composite were evaluated by FWO, KAS and IKP method. It indicates that the activation energy E of 4 % MRP/HDPE composite is higher than HDPE for three methods. MRP could improve the thermal stability and slow down the thermal degradation of HDPE. With adding MRP, the degradation mechanism of HDPE is changed and the degradation rate decreases.

Thermal degradation of High-Density Polyethylene Containing Cobalt Stearat as Oxidant Additive

Cobalt stearate can be used as an oxidant additive into High Density Polyethylene (HDPE). HDPE with the addition of 0.075% (w/w) of cobalt stearate was printed with a hot press. SEM results showed damage to the membrane surface which had been thermally degradation at 75 °C for 10 days. The TGA results also showed that the film had a weight loss of 75.99%. This decrease in weight indicated that an oxide compound had been formed due to the degradation of HDPE. The oxide compound is a chemical compound containing oxygen. With this oxygen, the degradation process of polyethylene will be easier and faster.

High-density polyethylene degradation into low molecular weight gases at 1823 K: An atomistic simulation

Using molecular dynamics simulation, we present a comprehensive study of the volatile thermal degradation of high-density polyethylene (HDPE) across a temperature range of 300K to 1823K. We find that degradation at temperatures higher than ∼1373K generates significant quantities of reducing gases such as CHn and hydrogen molecules which are beneficial to the steelmaking industry. Our results provide a new understanding of HDPE's phase transformation from solid to gas that occurs during superheating at steelmaking's electric arc furnace environment offering a new method for eliminating end-of-life HDPE from landfill.

Influence of fullerene on the kinetics of thermal and thermo-oxidative degradation of high-density polyethylene by capturing free radicals

The influence of fullerene (C60) on the thermal and thermal-oxidative degradation of high-density polyethylene (HDPE) was studied using non-isothermal thermogravimetric analysis under nitrogen (N2) and air atmosphere. Kinetic parameters of the degradation were evaluated using the Flynn–Wall–Ozawa method, which does not require the knowledge of the reaction mechanism. The results showed that the addition of C60 enhanced the thermal stability of HDPE and increased the activation energy both in N2 and air atmosphere and especially affected the initial stage of degradation. In N2, C60-trapped carbon-centered radical originated from the degradation of HDPE to improve the thermal stability and increase the activation energy. While in air, C60 trapped the alkyl radicals and alkyl peroxide radicals to inhibit the hydrogen abstraction (especially the initial stage of thermo-oxidative degradation) and form more stable species, which improved the thermal stability and increased the activation energy during the thermal degradation of HDPE. Comparing with that of pure HDPE, the changes of activation energy for HDPE/C60 nanocomposites were higher in air than in N2, especially in the initial stage.

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

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 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 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 of the degraded products had dropped to about 5 × 103g/mol from about 3 × 105g/mol for the original , and the product did not show the melting and crystallization behaviors of high density polyethylene again.

Enhanced Production of α-Olefins by Thermal Degradation of High-Density Polyethylene (HDPE) in Decalin Solvent: Effect of the Reaction Time and Temperature

The thermal degradation of high-density polyethylene (HDPE) in decalin has been investigated as a method for the feedstock recycling of plastic wastes. The study is focused on the effects of the reaction time and temperature. The solvent increased the HDPE conversion and had a significant effect on the product distribution, which may be assigned mainly to the decalin participation on the reaction mechanism. Short reaction times and low temperatures in the presence of decalin contributed to an enhanced production of gaseous hydrocarbons. Longer reaction times and high temperatures in the presence of this solvent improved the production of C5−C55 hydrocarbons. The gaseous olefins and C5−C32 α-olefins increased with time and temperature; however, the best selectivity to olefins (96.5%) in the gaseous fraction was obtained at 5 h and 375 °C, whereas the higher selectivity to α-olefins (76%) within the C5−C32 fraction was achieved after 5 h and 425 °C.

Fluidized bed thermal degradation products of HDPE in an inert atmosphere and in air–nitrogen mixtures

Different processes involving thermal decomposition such as incineration, pyrolysis, gasification or co-combustion are becoming important for energy generation using plastic wastes as combustible materials. The thermal degradation of the material, the product distribution and consequently the economics of the process are strongly influenced by the experimental conditions used. In this work, the thermal degradation of high-density polyethylene (HDPE) has been carried out using a fluidized bed reactor under different temperature conditions. Two types of experiments have been performed, pyrolysis experiments, in which nitrogen has been used as inert gas, and gasification experiments, meaning that the thermal decomposition has been carried out in a nitrogen–air mixture with low oxygen concentration. The influence of the operating parameters on the product distribution and gas composition has been investigated using GC and MS/GC for the analysis of the gas, wax and oil fractions obtained. The results obtained show a widely differing product yield in both processes. The main objective of the paper is a comparison of pyrolysis and gasification in terms of the generation of products of high heating value, and the energy requirements for the thermal degradation and production of residues and polyaromatic compounds. An optimum interval of operation temperatures is suggested in order to obtain high yield to gases of high heating values and low yield to PAHs.

Catalytic and thermal degradation of high-density polyethylene in vacuum gas oil over non-acidic and acidic catalysts

In this study, the conversion of HDPE in VGO to fuels was carried out in absence and presence of catalyst. The blend containing 20% HDPE was co-processed in presence of hydrogen at the temperatures of 435 and 450 °C. Five kinds of metal supported on active carbon catalysts (M-Ac) and acidic catalysts (HZSM-5 and DHC-8) were tested. The product distribution and the quality of liquid product changed depending upon the temperature and the type of catalyst. Among the metal supported active carbon catalyst, Co-Ac showed the highest cracking activity where as Mo-Ac showed the highest hydrodesulfurization activity. Co-Ac had better cracking activity than commercial hydrocracking catalyst (DHC-8). Although HZSM-5 had the best cracking effect in the hydrocracking of HDPE/VGO blend, the liquid product from HZSM-5 contained the highest sulphur. The use of carbon-supported metal catalysts in the co-processing of HDPE with VGO looks promising solution from an environmental viewpoint.

Binary Interactions between High-Density Polyethylene and 4-(1-Naphthylmethyl)bibenzyl during Low-Pressure Pyrolysis

Low-pressure pyrolysis experiments employing a high molecular weight polymer and a model compound for coal were conducted to address the effect of phase behavior on the overall degradation mechanism and reaction pathways during coprocessing. Thermal degradation of high-density polyethylene (HDPE) and 4-(1-naphthylmethyl)bibenzyl (NBBM) was conducted at 420 °C at different reactant loadings, both neat and in binary mixtures. During binary mixture experiments, there was an enhancement in the selectivities to primary products of NBBM at longer reaction times, with a significant reduction in the formation of secondary and tertiary products. These favorable interactions occurred because the polymer induced diffusion limitations in the system compared to neat NBBM pyrolysis, which minimized NBBM self-interactions and promoted reactions with the surrounding polymer. The degradation pathways of HDPE during binary mixture experiments were similar to those during neat reactions, with slight changes to the product y...

A kinetic analysis of thermal degradation of polymers using a dynamic method

A new method of kinetic analysis using a dynamic model which accounts for the thermal degradation of the polymer at any time, is proposed. The method was applied to predict the thermal degradation of high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) by a conventional nonisothermal thermogravimetric technique at several heating rates between 10 and 50°C/min. In addition, the various analytical methods reported in the literature were used in comparison with the kinetic analysis results obtained from the dynamic method. It was found that the dynamic method gave a reliable value of kinetic parameters, and the apparent activation energy and overall reaction order of HDPE were larger than those of LDPE and LLDPE.