Effect of some current antioxidants on the thermo-oxidative stability of poly(ethylene terephthalate) (original) (raw)
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Polymer Degradation and Stability, 2001
A comparative study was conducted into the thermo-oxidative degradation of poly(ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). Degradation of the polymer films and model compounds, ethylene dibenzoate (EDB) and butylene dibenzoate (BDB), was carried out in an oxygen atmosphere at 160 C. On the basis of the compounds identified by GC-MS a mechanism is proposed for the degradation of the model compounds that involves the oxidation at the a-methylene carbon with formation of unstable peroxides and carboxylic acids. From the studies performed under N 2 at 160 C it could be concluded that benzoic acid and esters are products of the thermal degradation, while benzoic and aliphatic acids, anhydride and alcohols are due to thermo-oxidative degradation. In contrast to the thermo-oxidative degradation of other polymers, for PET and PBT, especially at the beginning, thermal degradation plays an important role. The results clearly showed that PET is more stable towards degradation than PBT. #
Evaluation of effects of thymolphthalein on thermooxidative stability of polypropylene
2017
The present work is aimed to find a new and efficient type of antioxidants for polypropylene. Hence, effects of 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one, generally known as thymolphthalein, on thermo-oxidative stability of polypropylene in solid and melt states were evaluated and compared with those of SONGNOX 1010, an efficient commercially used antioxidant for the polymer. Oven ageing experiments followed by Fourier transform infrared (FTIR) spectroscopy showed that thymolphthalein increased thermo-oxidative stability of the polymer outstandingly in the solid state and its stabilization efficiency was comparable to that of SONGNOX 1010. In addition, measurements of oxidative induction time (OIT) and oxidation onset temperature (OOT) revealed that thymolphthalein improved thermo-oxidative stability of the polymer in the melt state significantly. It was also observed that thymolphthalein did not interfere with the stabilization action of SONGNOX 1010 in the...
A series of poly(ethy1ene terephthalate) (PET) samples was prepared from dimethyl terephthalate and ethylene glycol. In each sample a phosphorous compound was added as heat stabilizer after the transesterification and before the polycondensation. These compounds were: phosphoric acid, tributyl phosphate, triphenyl phosphate, phenylphosphonic acid, phenylphosphinic acid, and sodium phenylphosphinate. Firstly, their interference with the transesterification catalyst was examined. Their stabilization effect was estimated by DSC analysis in nitrogen and air. Various thermal criteria have been used, such as stabilization coefficient and induction period of oxidation. Under the conditions used for polymerization, the more efficient stabilizers were tributyl phosphate, phenylphosphonic and phenylphosphinic acid.
A comparative study on the thermo-oxidative degradation of poly(ether-esters)
Polymer Degradation and Stability, 2001
A comparison is made between the thermo-oxidative degradation processes in two copolymers of polybutylene terephthalate, one containing polyethylene oxide (PBT/PEO) and the other polybutylene oxide (PBT/PBO), in an oxygen atmosphere at 140 C. The degradation processes were followed by monitoring the oxygen uptake and CO/CO 2 formation during degradation and characterizing the degraded samples by GC-MS, FTIR and 1 H-NMR techniques. The formation of peroxides was measured titrimetrically. The presence of carboxylic acids and alcohols was detected by chemical treatment with SF 4 and NO, respectively. In order to gain more insight into the mechanism of the degradation, model compounds of each of these copolymers were used, namely diethyleneglycol dibenzoate (DEGDB) and dibutyleneglycol dibenzoate (DBGDB). The results are explained in terms of the initiation of oxidation at the methylene carbon vicinal to the oxygen ether, leading to the formation of new ester linkages. Simultaneously carbon-carbon and carbon-oxygen bond cleavage occurs, leading to aliphatic and aromatic carboxylic acids, formates and alcohols. #
Poly (ethylene terephthalate) thermo-mechanical and thermo-oxidative degradation mechanisms
Polymer Degradation and Stability, 2009
H NMR MALDI-TOF MS a b s t r a c t 1 H NMR and MALDI-TOF MS measurements were used to study the thermo-mechanical and thermooxidative degradation mechanisms of bottle-grade PET (btg-PET). In the thermo-oxidative degradation, the concentration of low molar mass compounds increased with time and the main products were cyclic and linear di-acid oligomers. In the thermo-mechanical degradation, the main-chain scission reactions affect the stability of the cyclic oligomers. One of the most important bottle-grade PET co-monomers is diethylene glycol (DEG), which is a ''reactive site'' in the thermal degradation of btg-PET. The DEG co-monomer was shown to be the precursor to colour changes in btg-PET, owing to the attack by molecular oxygen on the methylenic protons adjacent to the ether oxygen atoms of DEG. This behaviour was observed in the thermooxidative degradation process in which the degradation of DEG causes the release of hydroxyl radicals in the polymeric matrix, thereby producing mono-and di-hydroxyl substituted species. This was also observed in the thermo-mechanical degradation process.
Radiation Physics and Chemistry (1977), 1985
In part one of this series the effects of a phenolic, an amine and a thioester antioxidant on the thermo-oxidative stability of irradiated and unirradiated low-density polyethylene was reported. In this paper the effects of combined phenolic and thioester stabilizers are described. Isothermal thermogravimetric analysis was used to study the systems. Pronounced synergism was observed with the induction periods, the time when the initial weight loss begins and the 5% weight loss. At about 50% of each stabilizer increases greater than twofold were observed both with the unirradiated and irradiated polymers. The rate constants for oxygen uptake were decreased. However, the rates of degradation at 5% weight loss fell between the values of the two pure stabilizers with no pronounced synergism in either case. In the absence of oxygen little effect of either antioxidant or their mixtures was observed. The corresponding activation energies were somewhat higher, however, with the irradiated samples containing antioxidants. Dynamic thermogravimetry was used for this study. A kinetic analysis indicated that there were somewhat different modes of degradation at lower-and highertemperature ranges.
New catalyst for the synthesis of poly(butylene terephthalate) with high thermo-oxidative stability
Journal of Applied Polymer Science, 2007
In this paper we report the employment of Ti(acac) 2 (O-iPr) 2 (titanium bisacetylacetonate diisopropylate) as a novel catalyst for the synthesis of poly(butylene terephthalate) (PBT). Large scale synthesis of several polymers with the new catalytic system and with the standard catalyst Ti(O-nBu) 4 (titanium tetra-n-butylate) have been performed in a 20 L pilot plant. In the optimized reaction conditions, Ti(acac) 2 (O-iPr) 2 has shown significantly higher activity than standard catalyst, Ti(O-nBu) 4. Furthermore, a stabilized PBT has been synthesized in the presence of Ti(O-nBu) 4 as catalyst with the addition of the stabilizer U626. Then, the stability of the synthesized polymers toward thermo-oxidation has been tested in a forced circulating air oven. The polymers obtained in the presence of Ti(acac) 2 (O-iPr) 2 system showed higher stability towards thermo-oxidation than stabilized and not stabilized PBT, synthesized in the presence of Ti(O-nBu) 4 .