Spectra polyethylene terephthalate

Sometimes, small structural differences in morphology of polymer samples can be isolated by using a double subtraction technique. For example, with polyethylene terephthalate) PET, differences in the amorphous phase of the melt-quenched polymer and solution-cast polymer can be isolated by first subtracting out the contribution due to the trans isomer and then subtracting the two difference spectra from each other 214). (Fig. 16) shows the resultingdifference spectrum obtained after the second subtraction. Obviously the two amorphous structures are different from each other. 

Fig. 2. Cls core-level spectrum of a polyethylene terephthalate) film...

Figure 5. Decomposed ESCA carbon is spectra of Beulah lignite (—) and polyethylene terephthalate (—). Plot is of a number of electrons per energy in arbitrary units vs. binding energy in electron volts. The lignite spectrum has been corrected for sample charging (11).

A monomer needed to synthesize polyethylene terephthalate (PET), a polymer used to make plastic sheeting and soft drink bottles (Section 22.16), shows a strong absorption in its IR spectrum at 1692 cm" and two singlets in its h NMR spectrum at 8.2 and 10.0 ppm. What is the structure of this monomer (molecular formula CsHeO ) ... 

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... 

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

Pyrolysis and reforming of several types of common plastics (polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyurethane, and polycarbonate) were studied qualitatively, using a micro-reactor interfaced with a MBMS. Each type of plastic pyrolyzed at 550-750°C. This was followed by steam reforming of vapors in a fixed bed of C-11 NK catalyst at 750-800°C. The composition of the product gas (mass spectrum) was observed for different values of the steam-to-carbon mtio and space velocity that changed depending on the size of plastic samples. Preliminary tests showed that at process conditions similar to those used for reforming natural gas, polymers were almost completely converted to hydrogen and carbon oxides. 

Polyethylene terephthalate (PET) and polyethylene truxillate (PETx) were melt-mixed, 5delding a copolyester. The FAB mass spectrum was recorded, chain statistics was applied (Markoff distribution), and the extent of exchange (see above) was calculated. This study showed the potential of the MS... 

In a similar study, the FAB mass spectrum of a copolyester obtained by melt-mixing polyethylene terephthalate (PET) and of polyethylene adipate (PEA) was recorded. The authors computed the number average length of adipate and terephthalate blocks by applying chain statistics. The result was Uea = 7.1 Uet = 2 implying that the initial copolymer, obtained by meltmixing of the two polyesters, has a Markoffian (block) distribution of tire monomer sequence/ ... 

The two electrons transferred from TDAE to PEDOT-PSS are expected to undope the conjugated polymer chains. Since TDAE diffuses into PEDOT-PSS, long exposures to the electron donor induce changes in the optical properties of the polymer film. Optical absorption experiments on 200 nm thick PEDOT-PSS films coated onto a transparent polyethylene terephthalate (PET) substrate. The pol5mier film was exposed to the TDAE vapor in an inert nitrogen atmosphere and shows the difference in absorption spectrum between a film exposed to TDAE and the pristine PEDOT-PSS layer (Figs. 3.10 and 3.11). The modification of the optical properties and the sheet resistance of the pol5mier layer were recorded versus exposure time. The two absorption features at 550 nm and... 

Applied Spectroscopy 51, No.3, March 1997, p.346-9 AMPLITUDE SPECTRUM APPROACH IN DYNAMIC FT-IR SPECTROSCOPY OF UNIAXIALLY ORIENTED POLYETHYLENE TEREPHTHALATE FILMS. I. DRAW RATIO DEPENDENCE... 

For the accentuation of these small differences in the spectra of the stressed and unstressed polymer the absorbance subtraction technique has proved particularly useful. In Fig. 3 this is illustrated with reference to the 972.5 cm absorption band of the v(0—CH2) skeletal vibration of polyethylene terephthalate. Fig. 3 a shows the shape of this absorption band for the unstressed and stressed (300MN/m ) polymer. In the difference spectrum (see Fig. 3 b) the shift of the peak maximum toward lower wavenumbers and the low-frequency tailing are reflected by a pronounced asymmetrical dispersion-shaped profile. 

One of the most useful applications of FITR is the determination of the conformation of polymer chains. This is a result of the high sensitivity of the IR spectra to rotations around chemical groups. This is illustrated in Fig. 6.2, which shows the IR spectrum of the trans and gauche structures for the ethylene glycol portion of the polyethylene terephthalate (PET) chain. From these spectra, it is possible to determine the conformational composition for PET as a function of crystallization, annealing, and processing conditions. 

Normally, one would not usually consider that the change from an amorphous or glassy state to a crystalline or ordered state is readily discerned by infrared absorption. With some polymers, such as polyethylene terephthalate (PET), this change in structure gives rise to diffefrences in the infrared spectrum that can be used for quantitative analysis of samples for crystalline content. With PET, a band at 10.2 was shown by Cobbs and Burton [ ] to be a function of crystallinity and variously annealed samples were run for infrared absorption and density. The density of amorphous PET is 1.33, while the density for crystalline polymer is 1.47 according to x-ray unit cell measurements. From the density-infrared absorbance samples it was then possible to construct a calibration curve of absorbance versus percent crystallinity. 

The ATR method makes it possible to measure infrared spectra from the layer of the order of up to a few micrometers below a surface but it is also possible to extract information on a thinner layer by combining it with the method of difference spectrometry (see Section 6.2.3) in other words, the ATR method can be applied to more surface specific analysis. Figure 13.14a shows the ATR spectrum of polyethylene terephthalate (PET) covered with 0.05 pm-thick film of another material. The ATR spectrum of PET itself is shown in Figure 13.14b and the absorbance difference spectrum obtained by subtracting the spectrum in (b) from that in (a) is shown in Figure 13.14c. This spectrum is mostly due to the thin film covering the PET, and it is inferred from this spectrum that this surface-layer film is made of some kind of polyurethane. 

FIG U RE 4.57 The diamond ATR spectrum of a polymer film of polyethylene terephthalate, otherwise known as a soda hottle. 

The i.r. spectra of crystalline polymers tend to be sharper and more well-defined than those of their amorphous counterparts. In the case of polyethylene terephthalate certain bands have been found to be characteristic of the crystalline form of the polymer and others are found to be due to vibrations in amorphous polymer. This is because the molecules are all trans in the crystals whereas gauche conformations can exist in amorphous regions. The different conformations give rise to bands with different frequencies of absorption in the i.r. spectrum. 

---