The transmittance, absorbance, and reflectance of polypropylene (PP), polyethylene (PE), and polypropylene/polyethylene (PP/PE) blends prepared by a hot pressing method are investigated. IR and UV spectra of PP, PE, and PP/PE blends (0-80%) in the wavelength range of 200-25000 nm were examined. The optical absorption spectra are presented and the determined values of energy gaps are listed. The results indicate that both direct and indirect transitions may exist. The analyses of the absorption peaks corresponding to oxygen groups for the PP/PE composite (80/20) show low optical density and, therefore, highly different optical behavior than for pure PP. The PP/PE composite is very promising with regard to optical stability
In this study the mutual investigation of the results obtained from the mechanical stability properties and the IR spectra of polypropylene‐based but differently doped low‐density polyethylene (LDPE) and o‐o‐di‐n‐cresylditio phosphorous (CTPh) acid polymer composites is given. As opposed to the studies of the writers in recent years here, dynamical‐mechanical properties are explained not only by the variations in the oxidation peaks but also by the optical density in the peaks of the variations in the groups in amorphous and crystalline regions. The properties are also explained by the spectra variations in the IR region, which, according to Mamedov (2), is important, and by the extreme variations of the polymer properties. IR spectra analyses show that for both composites, (1) the optical density of the peaks in the crystalline regions for LDPE decreases while for PP those of the peaks in the amorphous regions increase; (2) the optical density of the peaks belonging to the CC groups get higher, whereas those of the peaks 1717, 1748 cm−1 diminish; and (3) the dynamical‐mechanical properties change accordingly, and these changed composites have the maximal characteristics, since the added amount is 0.2–0.3% CTPh by mass and 20–30%LDPE by mass. On the basis of the paper by Abdullayev et al. (3), the mechanism of these processes is given.
In this study, various effects on the properties of the material, such as free-radical (FR) processes, oxygen induction time (OIT), melting temperature and melting heat are examined during several stages of the polyethylene (PE) pipe extrusion process. The spectra in the Electron Spin Resonance (ESR) are researched between 77–293 K and in a wide range of magnetic fields. At 77 K a triplet signal in ESR is observed. The parameters of the signal are ΔHm1 ≅ 1:4 – 1:6 mT; ΔHm2 ≅ 1 – 1:2 mT; ΔHm3 ≅ 0:6 – 0:8 mT and g1 ≅ 2:020; g2 ≅ 2:011; g3 ≅ 1:99 and Hyper Fine Structure constant ΔH12 ≅ 2:1 mT; ΔH23 ≅ 5:3 mT. As the temperature increase from 77 K up to 293 K, the signal for g4 ≅ 2:02 (ΔHm4 ≅ 0:7 – 0:8 mT) appears and intensity of signals increase. It is also thought that the triplet observed at 77 K belongs to macroradicals of alkyl (–CH2–CH–CH2), alyl(~CH2 C HCH = CHCH2~), carboanions and the acyl (H C O) radicals of the fourth signal. At room temperature, all the FR's transform into peroxide radicals. The total concentration of the FR's is minimum at 463 K and increases at the outlet of the extruder and the pipe sample.It is observed that the OIT (Oxygen Induction Time) values decrease as one approaches the outlet of the extruder (from 20–30 to 10–15 minutes), while they increase for the processes of 433 K to 463 K. This event proves that the peroxide radicals form as one passes to room temperature. These results support those of the effects of the extrusion stage on the dynamic-mechanical characteristics [2].Finally, FR's appear as a result of the breaking of the C-C bonds in the main polymer chains starting from the first step in the extrusion process (433 K) and in the later stages, due to the oxygen in the polymer structure, oxidation processes take place.
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