Polyethylene Terephthalate Oligomers Research Articles

بررسی مهاجرت ترفتالات از بطری های PET روغن آفتابگردان, تولیدی کارخانه پارس

In Iran, the majority of vegetable oil producers , use PET for packaging their products . Due to high solubility of PET oligomers in the oils , and shelf life of liquid oils , it is expected that some compounds migrate into the oil . This study was carried out to determine the amount of migration of terephtalates from PET bottles into sunflower oil and the effect of temperature and storage time on the degree of migration. 42 samples of liquid sunflower oil packed in one litre PET bottles, from single production bach of pars vegetable oil, were kept at 20˚C and 40˚C. Experiments were carried out on three bottles taken at different periods of time (10, 20, 30, 70, 145 & 202days). According to Castle method , alkaline hydrolysis of all PET oligomers to terephthalic acid followed by its methylation to dimethylterephthalate (DMT) for the measurement of DMT, derivative UV spectrophotometer was used according to Reeves.The results showed that the maximum level of migration of terephthalates at 20 ˚C was 29.43 + 0.93 and at 40˚C was 29.58 + 1.15. Therefore the amount of overall migration obtained in this research is lower than the international permitted level (lower than 60 ppm) and sunflower oil after the final migration can be safely consumed. Migration increased with the passage of time until it reached to its highest level and then stopped (P=0). Migration is faster when the temperature is increased (P=0.014). Therefore, migration is dependant on both temperature and contact time (P=0.001). In this research, linear dependence between migration and square root of time has also been demonstrated (r = 0.96 at 20 ˚C from time zero to 145 days and r = 0.95 at 40˚C from time zero to 70 days). Reproducibility of the method was evaluated by calculating the relative standard deviation which was equal to 3.21% and the detection limit of the method was 0.21 ppm. In conclusion migration of PET oligomers was dependant on time and temperature, until it reaches an equilibrium. Keywords: Plastic bottle, Migration, Sunflower oil, Polyethylene terephthalate (PET), Derivative UV Spectrophotometry , PET oligomers.

A new look at the modification of polyethylene terephthalate by sodium hydroxide

Weight reduction is an alkali treatment of polyethylene terephthalate (PET) fabric with the aim of improving drape, handle and touch. The reaction of aqueous alkaline such as sodium hydroxide on PET is reported to be of the topochemical type meaning that the chemical reaction, hydrolysis, is limited to the fibre surface, and alkali does not affect the PET fibre core. Moreover, it is also reported that roughening of the fibre surface is a result of excess PET oligomers on the fibre surface after hydrolysis. New evidence obtained from small and wide angle X-ray scattering, wide angle X-ray scattering and atomic force microscopy reported in this article reveals that the bulk microstructure of PET is indeed affected by the weight reduction process and the roughening of the surface is a result of the new topology formed after weight reduction. A wide range of mechanical properties are measured. The wetting time is reduced from an average of 30 seconds to less than 1 second as a result of weight reduction. It was also found that dimensions of the PET fabrics were not affected by the weight reduction process.

Survey of formaldehyde, acetaldehyde and oligomers in polyethylene terephthalate food-packaging materials

Polyethylene terephthalate (PET) is frequently used as a packaging material for beverage bottles, fruit and vegetable trays, and egg crates in Japan. Levels of formaldehyde (FA), acetaldehyde (AA) and PET oligomers in various PET food packaging were determined. PET samples were initially dissolved in trifluoroacetic acid with 2,4-dinitrophenylhydrazine to derivatize formaldehyde and acetaldehyde to their dinitrophenylhydrazones. The stable derivatives along with the oligomers were analysed using HPLC with ultraviolet light detection at 360 and 254 nm, respectively. The PET pellets contained 3.5–12.4 µg g−1 AA and 4.0–7.2 mg g−1 oligomers, while FA was below the determination limit. FA, AA and oligomer levels in Japanese bottles were 0.6–3.0 µg g−1, 8.4–25.7 µg g−1 and 5.0–8.7 mg g−1, ND–1.6 µg g−1, 5.0–13.1 µg g−1 and 4.9–8.2 mg g−1 in French and Italian bottles, and ND–1.2 µg g−1, 9.1–18.7 µg g−1 and 5.6–8.0 mg g−1 in US and Canadian bottles, respectively. Compared with European bottles, Japanese bottles contain higher FA and AA levels. In sheet-moulding products, their contents were determined as ND–1.1 µg g−1, 11.5–43.1 µg g−1 and 4.6–9.2 mg g−1, respectively. The results show that sheet-moulding products contain lower FA and higher AA in comparison with bottles. FA and AA are considered to be generated from PET during the heating process for moulding the pellets to bottles or sheet-moulding articles and de-aeration during the sheet-moulding process is effective in removing FA. In contrast, the level of the oligomers remains unchanged during the moulding process from pellets to bottles or sheet products.

Synthesis of (polyethylene terephthalate/polyϵ-caprolactone) copolyesters

Polyethylene terephthalate (PET) was alcoholised with ethylene glycol to synthesize hydroxytelechelic oligomers of PET. On the other hand, commercial hydroxytelechelic polyϵ-caprolactone was modified in order to synthesize carboxytelechelic polyϵ-caprolactone. The chemical structure of the products was investigated by 1H NMR. Multiblock copolyesters were then synthesized by polyesterification of hydroxytelechelic PET and carboxytelechelic polyϵ-caprolactone oligomers, using several catalysts and different reaction conditions, which have been linked with the average molecular weight of the obtained block copolyesters. It appeared that residual distannoxane species coming from glycolysis step are best catalyst for polyesterification reaction. The chemical structure of the synthesized copolyesters was investigated by size exclusion chromatography and 1H NMR. The thermal and thermomechanical behavior of the synthesized copolyesters was investigated by differential scanning calorimetry and by dynamic mechanical analyses. The ester–ester interchange reaction between the two types of oligopolyesters has been enlightened and estimated taking in account the different reaction parameters. This side reaction led to the miscibility of the two phases of the oligomers, that can be explained by a random structure of the copolyester, and prevented to obtain multiblock copolymer.

Use of oligomeric wastes for the modification of epoxy resin

A series of polymer semi-interpenetrating polymer networks (semi-IPNs), based on different compositions of a PolyEthylene Terephthalate Oligomer (PETO) {Bis(2-HydroxyEthyl) Terephtalate} (BHET) and epoxy resin were prepared. These materials form a kind of blend in which microstructural, thermal, and tensile properties are shown to be dependent on composition. Also, Tg behavior of these semi-IPNs materials, as a function of concentration, follow the well-known Fox equation and this behavior explains quite well the solubility of the PETO in the epoxy resin.

THE HIGH-PRESSURE CRYSTALLIZATION AND ANNEALING BEHAVIORS OF POLYETHYLENE TEREPHTHALATE OLIGOMER

Polyethylene terephthalate (PET) oligomer samples crystallized and annealed at high pressure were investigated with differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that better crystals were obtained through high-pressure crystallization from the melt than annealing under the same conditions. The difference of the effects of crystallization and annealing on the morphology of crystals reduced with the increase of crystallization time. The melting temperature was determined by the lamellar thickness when it was shorter than the length of the molecular chains, while the main factor governing the melting temperature changed from lamellar thickness to density of chain-end defects when the lamellar thickness was much longer than the molecular length. PET oligomer extended-chain crystals with thickness up 100 μm were obtained.

Qualitative liquid chromatographic-atmospheric-pressure chemical-ionisation mass spectrometric analysis of polyethylene terephthalate oligomers

The oligomeric fraction of polyethylene terephthalate (PET) has been studied as it has the potential to migrate to foods and beverages packaged in virgin and recovered PET plastics. We have applied positive ion atmospheric-pressure chemical ionisation (APCI) to extracts of food-grade PET resin and beverage bottles. A reversed-phase HPLC system was connected directly to a VG Platform mass spectrometer. An acetonitrile-water-acetic acid gradient elution was performed. Low APCI probe temperatures (as appropriate for a polyethylene glycol calibrant) produced no significant ions from a PET cyclic trimer standard. A high probe temperature of 500–600°C gave a strong protonated molecular ion. Characteristic spectra of the cyclic oligomers from the trimer to the heptamer were obtained. A second homologous series of substances 44 mass units higher than each PET oligomers eluted prior to each PET oligomer. The mass spectra indicated these to be oligomers with one monoethylene glycol unit replaced by a diethylene glycol unit. To our knowledge this is the first time that cyclic oligomers above the tetramer have been confirmed by LC-MS. The technique was considerably more sensitive than published thermospray methods and gave food spectra with sub-microgram quantities injected. This work demonstrates the advantages of APCI over thermospray as an MS technique for substances of this type.

Modification of polyester resins by an oligomeric additive

Blends of unsaturated polyester resin (UP) and polyethylene terephthalate oligomers (PETO) have been prepared with different relative compositions. These materials form a kind of semiinterpenetrating polymer networks (semi-IPN's) in which the microstructure and the tensile properties are shown to depend on composition. Impact strength of the blends is also reported, and the performance of the blends was found to be superior to pure UP.

Semi-interpenetrating polymer networds produced with polyethylene terephthalate oligomer and unsaturated polyester resin

A series of semi-interpenetrating polymer networks (semi-IPN's) based on different compositions of an acyclic polyethylene terephthalate oligomer and unsaturated polyester resin (UP) were prepared. The oligomer was dissolved in the resin containing styrene crosslinker. Later this mixture was crosslinked at room temperature using methyl ethyl ketone peroxide catalyst and cobalt naphtanate as promoter. The tensile strength of the IPN's decreases as the concentration of oligomer increases, whereas, elongation to break increases. A characterization of the oligomer used is also presented.

Migration of Dibenzoate Plasticizers and Polyethylene Terephthalate Cyclic Oligomers from Microwave Susceptor Packaging into Food-Simulating Liquids and Food

Migration of diethylene and dipropylene glycol dibenzoate and the polyethylene terephthalate (PET) cyclic oligomers from microwave susceptor packaging into oils (food-simulating liquids) and food (french fries) has been determined. The PET susceptor film did not provide a barrier to migration of adhesive components when oils or food were cooked in contact with the PET susceptor film. The dibenzoate plasticizers migrated to a greater extent into oils and food then did the PET oligomers.

Migration into food of polyethylene terephthalate (PET) cyclic oligomers from PET microwave susceptor packaging

A quantitative method has been developed to measure the migration of polyethylene terephthalate (PET) cyclic oligomers from aluminized PET susceptor film-type food packaging into several food types. Microwaveable French fries, popcorn, fish sticks, waffles and pizza sold in susceptor-type packaging were purchased in local markets, cooked according to package instructions and analysed for PET oligomers. Appropriate food blanks were cooked in glass containers. Quantities of PET oligomers found in the foods ranged from less than 0.012 micrograms/g to approximately 7 micrograms/g.

The cyclic oligomers in polyethylene terephthalate

The cyclic oligomers in polyethylene terephthalate