Effect Of Gamma Irradiation On The Crystalline Structure Of Poly(Vinylidene Fluoride) (original) (raw)
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Gamma Irradiation Effects on Poly (Vinylidene Fluoride) Films
2002
In this work, the properties of Poly(vinylidene fluoride) PVDF films after exposing to gamma radiation at different doses (5, 10 and 15 kGy) were investigated. PVDF is a semicrystalline polymer that shows good properties in terms of chemical, thermal and electrical stabilities. The gamma radiation is a convenient and effective way of modification perfluorinated and partially fluorinated polymers such as PVDF. The properties of the pristine and irradiated PVDF films were studied by infrared spectroscopy, thermal analysis (TGA and DSC) and mechanical measurements at room temperature and at melting temperature of the PVDF. The infrared spectra of the irradiated PVDF samples do not present significant alterations in the absorption bands at all irradiated doses. The results obtained by thermal analysis indicate that the radiation does not alter significantly the decomposition temperature of the pristine PVDF film. Tensile strength measurements at room temperature before and after exposition to gamma radiation showed decrease of elongation at rupture in relation of pristine PVDF, suggesting that the radiation caused the crosslinking or chain scission of the PVDF film.
Changes in poly-vinylidene fluoride produced by electron irradiation
Radiation Physics and Chemistry, 1999
A study was made of the eects of electron irradiation of poly-vinylidene¯uoride, using the DSC, FTIR, and Xray techniques, as well as determining the percent cross-linking. Changes in crystallinity and melting point of the sample as a function of dose were found, the latter due to competition between cross-linking and crystallinity. The cross-linking was observed to increase with radiation dose. Chemical changes observed include the formation of carbonyl groups and double bonding, associated with the loss of HF. #
Structural Modifications of Gamma Irradiated Polymers: An FT-IR Study
A comprehensive study of structural modifications of gamma irradiated polymers in the dose range of 10 1 Gy to 10 6 Gy, was conducted using FT-IR technique. The results were varied in nature, proving that all polymers do not undergo similar type of destruction under similar irradiation conditions. The IR spectrum of polypropylene polymer confirmed the total destruction of isotactic arrangements of the polymer. The destruction of the polypropylene polymer lead to the formation of alcoholic and ketonic groups. For polyacetate polymer, elimination of carbon dioxide took place due to destruction of the ester group. Interestingly, for polycarbonate polymer also, it was observed that at the dose of 10 6 Gy, phenolic group formed due to cleavage of ester bonds. For polyvinyl chloride, there was a clear spectral indication regarding the formation of C=C bond and simultaneous decrease in concentration of C-Cl bond which took place upon gamma irradiation.
Increase in crystallinity in poly(vinylidene fluoride) by electron beam radiation
Journal of Polymer Science Part B-polymer Physics, 1987
We examine the influence of high-energy radiation and subsequent aging and orientation on the degree of crystallinity of poly(vinylidene fluoride) (PVDF) films. In particular, PVDF films were exposed to electron beam radiation (doses up to 50 W a d) and aged a t room temperature for varying lengths of time followed by uniaxial orientation. The degree of crystallinity of these films was found to increase significantly with increasing radiation dase. In addition, a further substantial increase in the degree of crystallinity was observed upon subsequent aging of irradiated films a t room temperature. Upon orientation, in addition to a further rise in the degree of crystallinity, the crystallits were observed to undergo the a form + p form transformation, the latter phase being the polar phase effective for piezo-electric/pyroelectric activity.
Changes in the physical and chemical properties of PVDF irradiated by 4 MeV protons
Revista Mexicana De Fisica, 2003
The behavior of poly-vinylidene fluoride (PVDF) under bombardment of different kinds of radiation is of interest due to the polymer's unique piezo-electric properties and various crystalline forms. In this work, PVDF film samples of 0.3 mm thickness and density 1.76 g/cm 3 were irradiated with 4 MeV protons from the Instituto de Física 9SDH-2 Pelletron Accelerator. Changes in the physical and chemical properties were investigated using Fourier Transform Infrared Spectroscopy (FTIR) with ATR, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and gel fraction measurements. The gel percent increases with fluence to almost 60% for a fluence of 10 13 cm −2 , and then more slowly up to 100% for a fluence of 3 × 10 14 cm −2. The DSC curve of the control sample shows a sharp band at 176 • C with a shoulder on the low temperature side. A well defined lower temperature peak, related to the relaxation of inter-crystalline regions appears at a fluence of 10 13 cm −2. At 3 × 10 14 cm −2 there are no melting peaks, due to complete destruction of the crystalline structure. This was confirmed at this high fluence by the FTIR spectra, and by x-ray diffraction, where an amorphous structure was observed.
Polymer Degradation and Stability, 1998
X-ray radiation-induced structural changes in the semicrystalline random copolymer poly(vinylidene fluoride-co-trifluoroethylene) (70-30) film were studied by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, ultraviolet/visible and infrared absorption spectroscopies and Raman scattering. The X-ray diffraction shows a decreasing degree of crystallinity with increasing X-ray irradiation times. The differential scanning calorimetry experiments show that the ferroelectric transition temperature Tc and the melting temperature Tm are lowered under X-ray irradiation. Thermogravimetric analysis shows one step weight loss with a decreasing decomposition temperature and increasing amount of residue with increasing irradiation times. The UV/vis spectra of irradiated copolymer film show the appearance of absorptions at ~192, 222, 272, 342 and 364 nm related to CC<, diene, triene and chromophores of radical ion species, respectively. Infrared spectra show a small high wavenumber shift for bands associated to CH stretching vibrations, decreasing intensities at 1293 and 852cm−1 and the appearance of new bands at 1847, 1750 and 1717cm−1, that increase in intensity with irradiation times. Raman spectra show an increasing fluorescence contribution with increase of irradiation time. A decreasing intensity of bands at 847 and 884cm−1 could be related to decreasing degree of crystallinity of the copolymer film. The X-ray irradiated P(VDF-TrFE) (70-30) films show physical and chemical change consisting in diminished degree of crystallinity, loss of ferroelectric property and the formation of new chemical structures (CC<, diene, triene and chromophores of radical ion species).
Effect of X-rays on poly(vinylidene fluoride) in X-ray photoelectron spectroscopy
Journal of Applied Polymer Science, 1998
The polymer poly(vinylidene fluoride) (PVDF) was irradiated with X-rays produced by a nonmonochromatic (MgKa) source and the structural and electronic PVDF surface modifications were studied by X-ray photoelectron spectroscopy (XPS). Changes in the shape and intensity of the C 1s and F 1s lines show that a PVDF degradation consisting of the polymer defluorination takes place.
Effects of gamma irradiation on poly(ethylene isophthalate)
Journal of Radioanalytical and Nuclear Chemistry, 2010
Radiation methods are largely used for polymerisation and polymer modification, since irradiation induces transformations in the structure of materials which can be exploited to improve their performance. On the other hand, combined action of ionising radiation and oxygen may lead to degradation of the polymer, with worsening of properties such as mechanical strength or electrical insulation resistance. Therefore, the change of the chemical and physical properties of polymers under irradiation is a dynamic topic of research. In this work there are discussed data on the physical features of a polyester, poly(ethylene isophthalate) (PEI), subjected to gamma irradiation up to 1 MGy. PEI is a semicrystalline polymer with a structure similar to polyethylene terephthalate. Viscosity and differential scanning calorimetry measurements were carried out which allowed the monitoring of changes in the structure in terms of variations in the molecular weight, as well as of the percentage crystallinity depending on the dose. Furthermore, positron annihilation lifetime spectroscopy supplied information on the free volume present in the amorphous phase of the irradiated polymer.
Characterization of gamma irradiated polyethylene films by DSC and X-ray diffraction techniques
Polymer International, 2000
The effect of gamma radiation on the thermal behavior and crystalline structure of low density polyethylene (LDPE) has been investigated using differential scanning calorimetry (DSC) and X-ray diffraction techniques (XRD). Gamma irradiation was carried out in atmospheric air to a maximum dose of 883 kGy. DSC results of the heating run from room temperature up to 150°C showed that the melting temperature (T m), and onset temperature of LDPE ®lm decrease linearly with increasing irradiation dose. However, upon cooling LDPE ®lm from 150°C to room temperature, the crystallization temperature (T c) and onset temperature were found to decrease non-linearly with increasing irradiation dose up to 500 kGy and then tended to level off. The change in heat of fusion (DH f) with irradiation dose was found to proceed with different behaviour, two stages, with a kink at irradiation dose of about 500 kGy, being observed. This suggests the occurrence of degradation and crosslinking at low and high doses, respectively. However, parameters of the X-ray diffraction pattern such as number of diffraction patterns, peak position (2u) and width of the diffraction pattern, support the results of DSC measurements.