Degradation Of PET Research Articles

Wplyw modyfikacji rezolowej zywicy fenolowo-formaldehydowej produktami chemicznej degradacji poli(tereftalanu etylenu) na jej wlasciwosci

There were synthesized the resol phenol-formaldehyde resins (PF) modified with various amounts (up to 20 wt. %) of the products of poly(ethylene terephthalate) [PET(N)] chemical degradation (glycolysis). NaOH or NH4OH solutions were used as reaction catalysts. Some physico-chemical properties of modified PF resins were determined (Table 1 and 2) and their structures have been confirmed using GPC method and IR spectroscopy (Figs. 1-5, Table 3). The resins contained very low amounts of free formaldehyde (ca. 0.2 %) and phenol (1.76-3.75 %) whereas dry mass content was in the range 66-80 %. Modified resins showed very good thermal stability (Table 4) and the varnish coatings made of them showed good adhesion to metal surface as well as elasticity and impact strength (Table 5 and 6). Application of PET degradation products to PF resins modification creates the possibility of PET wastes utilization and enables to obtain a new kind of resins showing good functional properties.

Analysis on the Degradation Behavior of Poly(ethylene terephthalate) in Extrusion System

In the melt spinning process of poly(ethylene terephthalate) (PET), extrusion conditions such as shear-flow history and thermal history influence the characteristics of resultant as-spun fibers. For the detailed analysis on the mechanism of thermal degradation of PET in fiber extrusion, an extrusion system consisting of a twin-screw extruder and a melt line equipped with three gear pumps and a draining channel was constructed to control the shear-flow history and residence time independently. Through the analysis of the effect of residence time, rate constants for the reduction of the degree of polymerization in the extruder and that in the melt line were estimated. The analyzed rate constant for the extruder was about three times higher than that for the melt line. It was also found that a certain degree of degradation occurring during the extrusion is independent of residence time. Estimated activation energies for the molecular weight reduction in the extruder and that in the melt line were similar. It was also confirmed that there was an acceleration of molecular weight reduction with an increase in the rotation frequency of the screw in the extruder. Heat and stress caused by the shear-flow are attributable for this result.

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. III. Methanolytic degradation

AbstractThe methanolytic degradation of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units was investigated. Random poly(ethylene terephthalate‐co‐nitroterephthalate) copolyesters (PETNT) containing 15 and 30 mol % nitrated units were prepared from ethylene glycol and a mixture of dimethyl terephthalate and dimethyl nitroterephthalate. A detailed study of the influence of the nitro group on the methanolytic degradation rate of the nitrated bis(2‐hydroxyethyl) nitroterephthalate (BHENT) model compound in comparison with the nonnitrated bis(2‐hydroxyethyl) terephthalate (BHET) model compound was carried out. The kinetics of the methanolysis of BHENT and BHET were evaluated with high‐performance liquid chromatography and 1H NMR spectroscopy. BHENT appeared to be much more reactive than BHET. The methanolytic degradation of PET and PETNT copolyesters at 80 °C was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and 1H and 13C NMR spectroscopy. The copolyesters degraded faster than PET, and the degradation increased with the content of nitrated units and occurred preferentially by cleavage of the ester groups placed at the meta position of the nitro group in the nitrated units. For both PET and PETNT copolyesters, an increase in crystallinity accompanied methanolysis. A surface degradation mechanism entailing solubilization of the fragmented polymer and consequent loss of mass was found to operate in the methanolysis of the copolyesters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2276–2285, 2002

Miscibility and Crystallization Behavior of Poly(ethylene terephthalate)/Poly(vinylidene fluoride) Blends

Poly(ethylene terephthalate) (PET) and poly(vinylidene fluoride) (PVF 2 ) are miscible in the meltstate for the whole composition range. The glass transition temperature (T g ) of the solvent cast film decreases with the decrease in W PET (weight fraction of PET) in the blend, however, the T g for the repeated melt quenched blends remains invariant with W PET . The melting point (T m ) and crystallization temperature (T c ) of PET decrease significantly with decrease in W PET in the blend, but the T m and T c of PVF 2 decrease slightly with increase in W PET . The crystallinity of both PET and PVF 2 decreases with increasing concentration of the other component in the blend, however, the decrease is larger for the former. The equilibrium melting points (T 0 m 's) of PET in the blends are determined by the extrapolation procedures using (i) T m - T c method for 5% crystallinity and (ii) T m -T a method, where T m , T c and T a are melting, crystallization and annealing temperatures, respectively. The data of both the methods indicate a large depression of T 0 m of PET with increase in PVF 2 concentration. The χ 12 values determined from both the data are essentially the same, -0.14. This negative value of χ 12 indicates that the two polymers are miscible in the melt-state, however, they are not miscible in the crystalline state. The onset of degradation of PET increases with increase in PVF 2 concentration in the blend.

The thermal degradation of PET and analogous polyesters measured by thermal analysis–Fourier transform infrared spectroscopy

The thermal degradation of two commercial poly(ethylene terephthalate) (PET) samples and two laboratory prepared polyesters, poly(ethylene isophthalate) and poly(diethylene glycol terephthalate), was studied using thermogravimetry and thermal analysis–Fourier transform infrared spectroscopy. The commercial PET samples were copolymerised with diethylene glycol and isophthalic acid groups in different proportions, and their thermal stabilities were found to differ. Through a study of the thermal degradation of poly(diethylene glycol terephthalate) and poly(ethylene isophthalate), it was found that diethylene glycol and isophthalate units promoted thermal degradation through increased chain flexibility and more favourable bond angles, respectively. The thermal degradation of all the polyesters tested lead to the formation of non-volatile residue. Infrared spectroscopic analysis indicated that the residue consisted almost exclusively of interconnected aromatic rings.

Temperature and atmosphere influences on smoke composition during thermal degradation of poly(ethylene terephthalate)

AbstractThe less‐volatile compounds forming a smoke emitted during the thermal degradation of poly(ethylene terephthalate) (PET) in different conditions were studied. Thermal degradation of PET was carried out within the temperature range of 200–700°C in both a nitrogen and an air atmosphere. The less‐volatile thermal degradation products were trapped on a glass‐fiber filter and analyzed by capillary gas chromatography with mass selective detector (GC‐MS) and high performance liquid chromatography (HPLC). The results are collected in tables and presented on plots as a function of the degradation temperature. The temperature and atmosphere effects on the emission and composition of the smoke during PET thermal degradation were considered. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3064–3068, 2001

Effects of mixing time on phase structure and mechanical properties of poly(ethylene terephthalate)/ polycarbonate blends

AbstractThe effects of interchange reactions on the solid‐state structure and mechanical properties of a 70/30 poly(ethylene terephthalate) (PET)/bisphenol A polycarbonate (PC) blend were studied. Increasing reaction levels were obtained by means of lower screw speeds in the extruder. The progressive production of copolymers with the reaction time increased the amount of each component in the other phase. The concomitant degradation of PET led to a maximum in ductility and tensile and impact strengths whereas the modulus of elasticity and the yield stress were held constant. The maximum in properties took place at a reaction time close to 2.6 min; at longer reaction times the negative effect of degradation began to overcome the positive effect of the interchange reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 121–127, 2001

Promotional effect of copper(II) chloride on the thermal degradation of poly(ethylene terephthalate)

The thermal degradation of fiber-grade powders, bottle-grade pellets, and waste bottle flakes of poly(ethylene terephthalate) (PET) samples were studied by a batch pyrolysis operation at atmospheric pressure. The degradation temperature of this work was in the range 350–500°C. Copper(II) chloride was found to be an effective additive for enhancing the degradation ability of these three kinds of PET samples. The percentage weight loss of these samples degraded with such an additive was in the order, fiber-grade powders>waste bottle flakes≥bottle-grade pellets. The methods of mixing PET sample and additive affect the extent of degradation of PET. For most cases, the impregnation method showed higher extent of degradation than physical mixing. The effect of other factors, degradation temperature and degradation time, on the extent of degradation of PET when copper(II) chloride was used as an additive was also investigated. Pyrolysis GC-MS was carried out at 445°C for 6 s to analyze the gaseous product distribution. The results showed that the gaseous products distribution of PET samples degraded with or without copper(II) chloride were little different. But the relative concentration of each gaseous product was changed.

Polyethylene terephthalate) Recycling with Organic Phosphates-I. Increase in Molecular Weight

Recycling of poly(ethylene terephthalate) by processing flakes obtained from post-consumer PET bottles was investigated. Flakes were additivated with organic phosphites during the processing in an internal mixer and the torque and temperature of the melt were monitored in each run. The molecular weight and polydispersity of the recycled PET were measured by viscometry and SEC. Some of the phosphites acted as chain extenders increasing the polymer M w . Best chain extension results were obtained with triarylphosphites, while dialkyl and trialkylphosphites promoted PET degradation. The study showed that triphenylphosphite was the best chain extender used in this work.

Volatile products of poly(ethylene terephthalate) thermal degradation in nitrogen atmosphere

Thermal degradation of PET was studied in a nitrogen atmosphere at 200–700°C. The experiments were carried out in a tubular furnace under isothermal conditions. The volatile substances evolved from PET were identified and quantified. Weight losses of PET during the thermal degradation in different temperatures were determined. The results are presented on plots as a function of the degradation temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1894–1901, 2000

Estudo da influência de resíduos catalíticos na degradação de plásticos reciclados (Blenda HDPE/PP e PET) provenientes de lixo urbano

A degradação derivada do processamento, uso, descarte, lavagem e reprocessamento foram caracterizados neste estudo. Para o HDPE/PP pós-consumo, a degradação foi estudada em função da presença de garrafas de HDPE/LDPE reprocessadas (recicladas) e da presença de tampas e rótulos de LDPE e PP. Esses materiais mostraram uma influência significativa na degradação total de HDPE/PP apenas quando presentes em conjunto. Os resíduos que apresentaram menor estabilidade termo-oxidativa foram os rótulos e tampas de LDPE e PP. As análises usadas na caracterização da influência destes resíduos foram espectroscopia do Infra-vermelho (IR) e Calorimetria Diferencial Exploratória (tempo de indução oxidativa - OIT). Além disso, a degradação do PET foi estudada em função das condições de lavagem e da presença de resíduos de soda cáustica e adesivo. Foram usadas medidas de viscosidade intrínseca e de titulação para caracterizar estas variáveis. Foi observado que apesar do uso de altas temperaturas (80 ºC) durante a lavagem, a extensão de tempo desta etapa (5 ou 15 min) não afetou a degradação do PET, pelo menos não em níveis detectáveis pelas análises. No entanto, a remoção do resíduo de adesivo mostrou uma influência significativa na degradação catalítica do PET.

Studies on degradation of PET in mechanical recycling

AbstractPET Poly(ethylene terephthalate) was processed repeatedly in a twin extruder. Effect of reprocessing on molecular structure of PET was evaluated in terms of reduction in molecular weight and mechanical properties. This study shows that weight‐average molecular weight Mw drops more notably compared with mechanical properties. Mechanical blending of virgin polymer with recycled PET was studied. The results of mechanical testings indicate that there is only slight loss in mechanical properties. The results suggest that mechanical recycling is a suitable method for recycling of PET for economic and environmental purposes.

Rigid polyurethane foams with poly(ethylene terephthalate)/triethanolamine recycling products

A product of the chemical degradation of poly(ethylene terephthalate) (PET) with triethanolamine was used as a polyol component for rigid polyurethane foam synthesis. Miscibility of the product with water, some polar organic solvents and commercial polyols was investigated. Viscosities of the product as a function of temperature as well as in solutions with water and the polyols were examined. The PET chemical recycling product was used instead of the commercial polyol in rigid polyurethane foam formulation. Technological times were defined for the process of the foam synthesis. These foams have density of about 30 kg/m3, compression strength in a range of RC = 80–160 kPa and thermal conductivity coefficient λ = 0.028–0.038 W/m K. Rigid polyurethane foams prepared from the product of PET degradation with triethanolamine can be considered as insulation materials. Copyright © 1999 John Wiley & Sons, Ltd.

New trends in chemical recycling of poly(ethylene terephthalate)

AbstractChemical recycling of poly(ethylene terephthalate) (PET) by nonconventional transesterification and ammonolysis/aminolysis methods are discussed on the basis of literature and own experimental data. The obtained products of deep PET degradation using allylamine (N,N′‐diallylterephthaldiamide), triethanolamine and other alkanolamines were prepared and characterized by DSC and elemental analysis.

Studies of temperature influence on volatile thermal degradation products of poly(ethylene terephthalate)

The temperature influence on the thermal degradation products evolved from poly(ethylene terephthalate) (PET) was investigated. The experiments were carried out within the temperature range of 200–700°C in air. The main volatile toxic products and weight losses during thermal degradation of PET were determined. The results are presented on plots as a function of the degradation temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2377–2381, 1998

Microwave irradiation as an energy source in poly(ethylene terephthalate) solvolysis

Solvolysis by glycols and alcohols is an established method for the chemical recycling of poly(ethylene terephthalate) (PET). In our work, we investigated the use of microwave radiation as the energy source in PET solvolysis reactions, and the conditions that govern its effectiveness. The main advantage of microwave use are short reaction times, between 4 and 10 min, in which complete PET degradation is achieved. Solvolysis reagents used were methanol, propylene glycol, and polyethylene glycol 400. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1115–1118, 1998

Microwave irradiation as an energy source in poly(ethylene terephthalate) solvolysis

Solvolysis by glycols and alcohols is an established method for the chemical recycling of poly(ethylene terephthalate) (PET). In our work, we investigated the use of microwave radiation as the energy source in PET solvolysis reactions, and the conditions that govern its effectiveness. The main advantage of microwave use are short reaction times, between 4 and 10 min, in which complete PET degradation is achieved. Solvolysis reagents used were methanol, propylene glycol, and polyethylene glycol 400. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1115–1118, 1998

Grafting to achieve flame retardancy

Vinyl monomers, such as methacrylic acid, may be grafted onto styrenebutadiene copolymers, SBS, or onto acrylonitrile-butadiene-styrene terpolymer, ABS, by either a photochemical process or chemical initiation. The amount of grafting is similar using both procedures. Vinyl monomers may not be grafted onto poly(ethylene terephthalate), PET; rather the vinyl monomers homopolymerize within the PET and form a semi-interpenetrating network. All of these copolymers have been analyzed by TGA and TGA-FTIR. For SBS and ABS, the grafted char-former serves to retain the base polymer. There is little difference in the degradation pathway between the grafted and the virgin polymers. Homopolymerization of methacrylic acid within the PET matrix has no effect on the degradation of PET. When one attempts to convert the methacrylic acid contained within the PET into its sodium salt, the entire sample is hydrolyzed. There is good reason to think that the addition of a surface layer of a good char-former onto a polymer will improve the thermal resistance of the polymer.

Melt viscosity reduction of poly(ethylene terephthalate) by solvent impregnation

The melt viscosity of poly(ethylene terephthalate) (PET) was decreased by the impregnation of an aromatic solvent, such as l-methyl naphthalene or diphenyl ether. Porous PET granules for impregnation of the solvent were prepared by swollen-state polymerization in hydrogenated terphenyl as the swelling solvent. The PET granules could take up 20% of the solvent by heating with the solvent. On the other hand, PET granules polymerized in the solid-state scarcely absorbed the solvent, except for l-methyl naphthalene. The apparent melt viscosity of PET decreased to 1/5 by the impregnation of l-methyl naphthalene (20%). The solvent-containing PET granules allowed extrusion at lower temperature (270°C), which led to a reduction of the degradation of PET and produced high tensile strength (2 GPa) and high modulus (30 GPa) fibres.

Thermal degradation of polyethylene mixed with poly(vinyl chloride) and poly(ethyleneterephthalate)

Thermal degradation of plastics such as polyethylene (PE), poly(vinylchloride) (PVC), poly(ethyleneterephthalate) (PET) and their mixtures (PE + PVC and PE + PET) was studied at 430 °C by batch operation to analyse the conversion of waste plastics into fuel oil. A visual inspection of the inside of the reactor was made and the macroscopic process of degradation was monitored. Products of degradation were classified into three groups: gases, liquids and residues in the reactor. The degradation of PE produced liquid products which consisted of C 5-C 25 fraction of hydrocarbons with a yield of 70 wt%. On the other hand, the degradation of PVC produced only 4.7 wt% liquid products which consisted of C 5-C 20 fraction of hydrocarbons and the degradation of PET produced no liquid products. The effect of mixing PVC and PET with PE on the yield and compositions of liquid products was investigated. The addition of either PVC or PET to PE decreased the overall liquid products yield; however, it promoted the degradation of PE into low molecular weight liquid hydrocarbon products.