Polyethylene terephthalate irradiated

Such a reaction has been shown to give 1-butene and carboxyl groups in equivalent yields (about 2 x 10-2) in the liquid-phase photolysis of undiluted di-n-butylterephthalate [116]. From Table 4 it can be seen that the quantum yields of chain scission and of carboxyl group formation are almost identical this suggests that reaction (22) is the main cause of chain scission in the photolysis of polyethylene terephthalate. It must also be pointed out that reactions (19) and (21) do not necessarily yield chain scission, since the probability of the macro-radicals escaping the cage is rather low in a rigid matrix. Indeed, the appearance of an absorption maximum near 775 cm-1 in the infrared spectrum of polyethylene terephthalate irradiated at 313 nm has been ascribed to... 

With the exception of ethylene vinyl acetate added in the 1980 s, the list of materials and polymers approved as packaging for food irradiated products has remained static for decades. This article supplies details of the approved list, which includes such polymers as polyethylene terephthalate and polyvinyl chloride. The article provides an update on the latest proactive move to expand the list of packaging materials and polymers approved for the irradiation of foods. The expanded list would include ethylene vinyl alcohol, PVC film, ionomers, nylon 66, 6/12 and copolyesters among others. 

T wo aspects of the radiation chemistry of polyethylene terephthalate (PET) are reviewed here the dependence of product yields on radiation dose and on dose rate. The review is limited to work with thin films from which air and water were pumped prior to irradiation. Moreover, it is judged that in the experiments described postirradiation effects were negligible. 

When a polymer film is used as a substrate, aqueous Ti02 paste without organic surfactants is sintered at relatively low temperatures, with approximately 150°C being sufficient to produce mechanically stable 2 films. Sommeling et al. at ECN used an ITO-coated polyethylene terephthalate) (PET) film as a substrate and prepared a plastic DSSC [164-167]. A cell performance with a 7 of 15 pA/cm2, Voc of 0.48 V, and ff of 0.67 was obtained at an illumination intensity of 250 lux. This performance is sufficient for a power supply for indoor applications such as watches and calculators. Under AM 1.5 irradiation, a Vtx of 0.7 V and /sc of 2 mA/cm2 were obtained. 

In addition, such a method of synthesis can be generated by making use of another destructive means for ligand synthesis. In that sense, the method was verified by achieving some polycondensation products of polyethylene terephthalate and ethylenediamine and their complexation with different metals by irradiating the system with cobalt-60 (gamma rays). These results also make up the subject of other studies. 

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

Polyethylene terephthalate film (Mylar) is often used at cryogenic temperatures for electrical- or thermal insulation, as described in the preceding section. However, the radiation tolerance of Mylar is rather poor as shown in Fig. 5. Takamura and Kato reported that Mylar was too brittle to handle after irradiation of 6.2 x 106 Gy at 5 K [45]. 

FIGURE 43.7 Examples of porous structures produced in thin polymeric films using various methods of irradiation and chemical treatment. (Reprinted from Apel, P., Radial. Meas., 34, 559, 2001. With permission from Elsevier.) (A) Cross section of a polycarbonate membrane with cylindrical nonparallel pore channels (B) polypropylene membrane with slightly conical parallel pores (C) polyethylene terephthalate membrane with cigar-like pores and (D) polyethylene terephthalate membrane with bow-tie pores. 

Komolprasert V, McNeal TP, Begley TH. Effects of gamma- and electron beam irradiation on semi-rigid amorphous polyethylene terephthalate copolymers. hood Addit Contain 2003 20(5) 505 17. 

From Table I it is clear that polystyrene (PS) and polyethylene terephthalate (PET) are much more resistant to y-rays than polypropylene (PP), low density PE (LDPE), poly(oxymethylene) (POM), poly(vinyl acetate) (PVAc), poly(propylene oxide) (PPOx), and somewhat more resistant than poly(methyl methacrylate) (PMMA) or 6-6 nylon. A very commonly used plastic, poly(vinyl chloride) (PVG), is perhaps the least resistant of all the plastics giving off hydrogen chloride with quite a high G-value when irradiated. 

Polyethylene terephthalate becomes crosslinked and partly insoluble in o-chlorophenol [113] or trifluoracetic acid [114] when irradiated with... 

The electron spin resonance spectrum of irradiated polyethylene terephthalate has tentatively been assigned to radicals... 

Formulations were prepared by dissolving the base resin in 100 phr of 2-butanone, then adding the photoinitiator and any monomers to the resin solution. Films were cast from the resin solution onto 75 urn polyethylene terephthalate (PET) sheets, dried in a convection oven at 60°C for 15 minutes to remove residual solvent, and cured. A LESCO C612 conveyor system with Fusion Systems F450-10 irradiator was used for curing. A 300 W/inch Fusion "V" lamp was used in all experiments. Cure dose was varied by changing belt speed at constant irradiator power. 

K.A. Tawab, S.M. Ibrahim, M.M. Magida, The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA). J. Radioanal. Nucl. Chem. 295, 1313-1319 (2013)... 

The fibre must also be able to withstand prolonged exposure to sunlight, specifically irradiation by UV light. The twin considerations of thermomechanical stability up to 200 °C and resistance to UV radiation do rule out several types of commodity fibre. These fibres include most natural fibres, as well as commercial polyolefin and acrylic fibres, all of which melt or begin to decompose below 200 °C. Nevertheless, polyethylene terephthalate (PET) fibres are potentially suitable substrates they melt at 260-270 °C and exhibit good stability to UV radiation [6]. They are also commercially... 

The dominant effect of high energy irradiation on a polyester is chain scission, although both crosslinking and scission occur. With the aromatic polyesters such as polyethylene terephthalate (PET) and polybutylene tereph-thalate (PBT) the aromatic groups will act as protection, and the yields of any process will have a tendency to be low. 

Buchalla, R. Begley, T.H. Characterization of gamma-irradiated polyethylene terephthalate by liquid-chromato-graphy-mass-spectrometiy (LC-MS) with atmospheric pressure chemical ionization (APCI). Radiat. Phys. Chem. 2006, 75, 129-137. 

In many cases, plastics degrade in the presence of oxygen at irradiation doses that are without influence or result in crosslinking in vacuum. Because of oxidation, ultimate tensile strength and strain at break in polyethylene, polypropylene, polyvinyl chloride, polystyrene and in styrene-copolymers decrease faster with increasing doses when irradiated in air than when irradiated in a vacuum, whereas this is not the case for polyethylene terephthalate, polyvinyl alcohol, and acetyl cellulose. Oxidative degradation is also the reason for radiation damage doses that are notably smaller when irradiated in air than when irradiated in a vacuum [711],... 

Polyethylene terephthalate is relatively resistant to ionizing radiation. More noticeable degradation occurs at radiation doses higher than 100 kGy. During irradiation, crosslinking and degradation occur simultaneously in polyethylene terephthalate [32]. 

Figure 5.147 Radiation resistance of 80 fjm thick polyethylene terephthalate films irradiation in a vacuum at 5000 kGy/h with 1 MeV electrons from a van de Graafgenerator and irradiation in...

Demertzis and co-workers [48] carried out an in-depth study of the influence of gamma irradiation on the formation of solvent extractable radiolysis prodncts of flexible films and sheeting for food packaging. The packaging, which was made from PE, PP, polyethylene terephthalate (PET), PS, polyvinylchloride (PVC) and polyamide (PA), was subjected to Co irradiation at a dose of 44.0 kGy. Separation and identification of extracted compormds were carried out using GC-MS and compositional changes in the radiolysis prodncts quantified by calibration using MS detector response. 

Figure 9 Ultraviolet spectral absorption of 2 mil polymer films and spectral irradiance of sunlight. Abbreviations PVC, Polyvinyl chloride PE, polyethylene PS, polystyrene PC, polycarbonate AP, aromatic polyester PSF, polysulfone PET, poly(ethylene terephthalate) PAR, polyacrylate. Source From Ref. 16.

Surface oxidation reactions have been carried out on a number of polymers, particularly polyethylene. Surface oxidation techniques include the use of corona discharge, ozone, hydrogen peroxide, nitrous acid, alkaline hypochloride, UV irradiation, oxidizing flame, and chromic acid The reactions lead initially to the formation of hydroperoxides, which catalyze the formation of aldehydes and ketones and finally, acids and esters. Surface oxidation treatment has been used to increase the printabdity of polyethylene and poly(ethylene terephthalate) and to improve the adhesion of polyethylene and polypropylene to polar polymers and that of polytetrafluoroethylene to pressure-sensitive tapes. Surface-oxidized polyethylene, when coated with a thin film of vinylidene chloride, acrylonitrile, and acryhc acid terpolymers becomes impermeable to oxygen and more resistant to grease, oil, abrasion, and high temperatures. The greasy feel of polyethylene has also been removed by surface oxidation. 

Irradiation of polyethylenes (PEs) could lead to graft some oxidized species on the polyethylene backbone. This treatment was performed in order to improve the compatibility of polyethylenes toward polar polymers as poly(ethylene terephthalate) or polyamide Irradiation in air of... 

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