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1.
Kinetic studies of PET glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have shown, in a previous study, that the order of reactivity of the glycols differs according to the conditions of temperature and catalysis. Indeed, their global reactivity depends both on their chemical reactivity and physico-chemical properties.Glycolysis of model polyesters which are liquid at the reaction temperature, which allows us to overcome the problem of the polyesters' solubility, were studied to compare the chemical reactivity of these glycols. Three oligoesters were synthesized from dimethyl terephthalate and three different glycols namely triethylene glycol, ethylene glycol and hexanediol to form, respectively, PE3T, OET and PTHD.Results showed that the order of reactivity of the glycols is the same for PET, OET and PTHD but different for PE3T. Indeed, DPG without catalyst has a particular and unexpected behaviour: its reactivity seems to be strongly influenced by the presence of oxygen atoms in the chain. 相似文献
2.
Kinetics of poly(ethylene terephthalate) glycolysis by diethylene glycol. I. Evolution of liquid and solid phases 总被引:1,自引:0,他引:1
The kinetics of uncatalysed glycolysis, at 220 °C, of poly(ethylene terephthalate) (PET) by diethylene glycol (DEG) in high excess has been studied. An experimental device allowing good separation, at reaction temperature, of the solid and liquid phases was set up.The results suggest that PET is initially depolymerized in the slightly swollen solid phase, by glycolysis of the amorphous interlamellar chains. This mechanism continues until a solid phase of highly crystallized polyester is obtained.The internal tensions engendered by this chemical modification cause cracks, delamination and mechanical disintegration of the polymer. The transfer towards the liquid phase is then strongly accelerated and the solvolysis of the depolymerization products continues in the liquid phase, up to equilibrium. 相似文献
3.
The kinetics of poly(ethylene terephthalate) (PET) glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have been studied with two experimental procedures: uncatalysed at 220 °C and catalysed at 190 °C. An experimental device was set up allowing the isothermal kinetics to be monitored. A precise initial reaction time was obtained by separately warming the glycol and the polyester at the temperature of reaction before mixing them.The reactivity order of different glycols varies according to the conditions of temperature and catalysis. Schematically, the global reactivity does depend not only on the chemical reactivity of the glycol but also on its physico-chemical properties: ability to solvate the solid polyesters and polarity of the reaction mixture. Attempts to find synergic effects failed for almost all mixtures, except the mixture DPG + Gly in which the PET is digested more quickly than in pure DPG or Gly. 相似文献
4.
George P. Karayannidis Dimitris S. Achilias Irini D. Sideridou Dimitris N. Bikiaris 《European Polymer Journal》2005,41(2):201-210
In this investigation the production of secondary value-added products, such as alkyd resins, derived from the glycolysis of poly(ethylene terephthalate) (PET) is examined as an effective way for its recycling. PET was taken from common soft-drink bottles and diethylene glycol (DEG) was used for the depolymerization at several initial molar ratios. The oligomers obtained were analyzed according to their average molecular weights. Furthermore, the glycolyzed PET products (oligomers) were reacted with maleic anhydride, phthalic anhydride and propylene glycol to form unsaturated polyester resins. These were subsequently mixed with styrene and cured using the benzoyl peroxide/amine initiator system to carry out the reaction in ambient temperature. The curing characteristics of the resins produced were investigated with respect to the initial molar ratio of DEG/PET as well as the initial initiator concentration. Finally, the mechanical properties (tensile strength and elongation at the break point) of the resins were compared with the conventional general purpose resin and were found to be comparable. 相似文献
5.
PET做为一种常用的塑料制品,已经使用了很多年,在为人类生产生活提供便利的同时也产生了环境污染。通过微波降解PET具有效率高、时间短、产率高的特点,本文通过微波研究乙二醇的降解,并得出最佳反应条件。 相似文献
6.
Gopal Jeya Ravikumar Dhanalakshmi Murugan Anbarasu Viswanathan Vinitha Vajiravelu Sivamurugan 《印度化学会志》2022,99(1):100291
Chemical recycling of plastic wastes is top among the effective management of the solid wastes. Particularly the post-consumer polyethylene terephthalate (PET) plastic wastes mainly generated from the disposal of beverage bottles and placed third most produced polymeric waste. However, PET wastes could be chemically recycled using several types of homo-/heterogeneous acid or base catalysts, and an effective recycling process has yet to be achieved. Therefore, the present short review is intended to display recent reports on the depolymerization of PET polymer wastes. The review aimed to cover glycolysis and aminolytic depolymerization using various catalytic systems. There is a wide spectrum of catalytic systems such as metal oxides, ionic liquids, organic bases, nanoparticles, porous materials and microwave-assisted rapid depolymerization methods have been developed toward the yield enhancement of the depolymerized products. Ideologically, the present review would benefit the researchers in familiarizing themselves with the latest developments in this field. 相似文献
7.
We have studied the effect of advection on reaction–diffusion equations by using toroidal velocity fields. Turing patterns formation in diffusion–advection–reaction problems was studied specifically, considering the Schnackenberg and glycolysis reaction kinetics models. Four cases were analyzed and solved numerically using finite elements. For glycolysis models, the advective effect modified the form of Turing patterns obtained with diffusion–reaction; whereas for Schnackenberg problems, the original patterns distorted themselves slightly, making them rotate in direction of the velocity field. We have also determined that the advective effect surpassed the diffusive one for high values of velocity and instability driven by diffusion was eliminated. On the other hand the advective effect is not considerable for very low values in the velocity field, and there was no modification in the original Turing pattern. 相似文献
8.
Kinetics of poly(ethylene terephthalate) glycolysis by diethylene glycol. Part II: Effect of temperature, catalyst and polymer morphology 总被引:1,自引:0,他引:1
The influence of various parameters on the kinetics of poly(ethylene terephthalate) (PET) glycolysis by diethylene glycol (DEG), namely temperature (from 190 to 220 °C), temperature profile, catalysis and PET morphology has been studied.The results showed a strong influence of some experimental conditions (temperature and catalysis) on the mixture evolution during depolymerisation. The temperature study showed a critical temperature between 210 and 220 °C which seems to be the consequence of a better diffusion of DEG in PET, allowing easier reactions in solid phase. The initial morphology of PET scraps does not affect the rates of reactions much, in contrast to the temperature profile which has a great importance: time of PET dissolution at 220 °C is considerably shorter by heating PET and DEG separately at 220 °C before mixing, than by heating a cold mixture of the two reagents to 220 °C. 相似文献
9.
Minerva Monroy-Barreto Margarita Romero-Ávila Jesús Recillas-Mota 《International Journal of Polymer Analysis and Characterization》2017,22(1):11-16
The degradation of polyethylene terephthalate (PET) bottles has been successfully achieved by depolymerization through glycolysis with pentaerythritol. The reaction was performed at 250°C in the presence of an organotin catalyst. The glycolyzed products were characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The existence of the chemical bond between the polyol and the PET was detected through heteronuclear multiple bond correlation spectroscopy, and the NMR signals of different species were separated according to their diffusion coefficient by diffusion-ordered spectroscopy. This method offers a rapid quantification of glycolyzed products. Furthermore, it was found that the major product was the mono-pentaerythritol ester followed by the di-pentaerythritol ester, and lastly the tri-pentaerythritol ester. 相似文献
10.
K. El Gersifi 《Polymer Degradation and Stability》2006,91(4):690-702
The chemical recycling by solvolysis of epoxy resins, in particular those of the type including bisphenol A diglycidyl ether (DGEBA) cured by anhydrides, appears rather easy. The association of titanium(IV) n-butoxide (TBT) and diethyleneglycol (DEG) catalyst/solvent system proved effective. The depolymerisation of a model matrix, as well as composite waste, is pushed practically to the monomer stage. The glycolysis products are constituted by esterdiols, tetraalcohols and excess of glycol. The excess solvent can be eliminated by distillation under vacuum, without re-equilibration reactions towards the formation of higher molar mass species. Solvolysis by monoethanolamine (MEA) has also been studied. The reaction is more effective but the depolymerisation products are solid. Characterization of the depolymerisation products by NMR and Maldi-Tof has confirmed the reaction mechanism of transesterification and the presence of other alcoholysis side reactions. 相似文献