Gamma irradiation of polyester films (original) (raw)
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Effect Of Gamma Irradiation On Poly(Butylene Naphthalate) Based Polyesters
Radiation Physics and Chemistry, 2016
The present work investigates the effect of gamma radiation on the properties of three naphthalate-based polyesters, i.e. poly(butylene naphthalate) (PBN), poly(diethylene naphthalate) (PDEN) and poly(thiodiethylene naphthalate) (PTDEN). In addition, the analogous terephthalate-based polymers of PDEN and PTDEN, i.e. poly(diethylene terephthalate) (PDET) and poly(thiodiethylene terephthalate) (PTDET), are also investigated, in order to check the effect of a lower number of aromatic rings. All the polymers, irradiated in air at different absorbed doses, were characterized by several techniques. The data obtained indicate that all the polymers, except PBN, show a decrease of molecular weight with the dose increase. The thermal behavior and the morphology confirm the previous results and show that the higher the crystallinity degree and number of aromatic rings, the higher the radiation resistance. The introduction of heteroatoms decreases the ability of a polymer to crystallize due to a reduction of polymer chain symmetry, thus worsening their radiation resistance.
Gamma irradiation of PolyEthyleneTerephthalate and PolyEthyleneNaphthalate
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 2007
The effect of gamma irradiation in air is investigated in two thermoplastic polyesters (PET and PEN), in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. EPR measurements were carried out to detect radical stability against oxygen permeation and to provide radical characterization. Viscometric data reveal a different behaviour between films and thick samples. Positron annihilation spectra show a decrease of ortho-positronium intensity, which is more marked in film samples. ortho-positronium lifetime does not depend on the radiation dose.
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.
Irradiation effects on aromatic polymers: 1. Gas evolution by gamma irradiation
Polymer, 1992
The effects of gamma irradiation on aromatic polymers, such as polyimides (Kapton, Upilex-R and Upilex-S), poly(aryl ether ether ketone) (PEEK), poly(aryl ether sulphone) (PES), bisphenol A type Udel poly(aryl sulphone) (U-PS) and poly(aryl ester) (U-Polymer), were investigated based on gas evolution. The radiation resistance in terms of gas evolution was in the following order:
Irradiation effects on aromatic polymers: 3. Changes in thermal properties by gamma irradiation
Polymer, 1992
The effects of gamma irradiation under vacuum on the thermal properties and crystallization behaviour of poly (ether ether ketone) (PEEK-a, amorphous; PEEK-c, crystalline) have been investigated by d.s.c. The glass transition temperature for PEEK-a and PEEK-c increased on gamma irradiation, indicating that crosslinking is the main radiation mechanism for PEEK. The heat and temperature of crystallization for PEEK-a slightly changed on irradiation, indicating that the thermal crystallization process was inhibited by crosslinks because of the restriction in chain mobility. The heat and temperature of recrystallization for PEEK-a and PEEK-c on cooling from the molten state also decreased on irradiation and this is good evidence for crosslink formation in the PEEK structure. The disorder in chemical structure caused by crosslinking resulted in a lowering of the heat and temperature of melting. The effect of crystalline domains on the recrystallization behaviour of PEEK-a and PEEK-c was investigated and the effect of irradiation on the isothermal crystallization of PEEK-a and PEEK-c was also studied.
Study of the effect of gamma irradiation on polyolefins—low-density polyethylene
Polymer Degradation and Stability, 2002
Many of the physical, chemical and utility properties of polymer materials can be altered by means of high energy radiation such as gamma-rays, neutrons and electron beams. In the present work the exposure to gamma radiation of a bulk virgin low density polyethylene (LDPE) was carried out at various doses up to 2000 kGy. The study of the irradiation effects on the material properties has been make by different methods in an integrated way. The experimental data indicate that the gel content, the hardness and the yellowing increase with gamma radiation dose and that the LDPE gamma irradiation process involves crosslinking at lower doses and chain scission at higher doses. The final results show the reliability of gamma radiation as a practical method for the control of long-term properties. #
The Effect of Irradiation on Mechanical and Thermal Properties of Selected Types of Polymers
Polymers, 2018
This article deals with the influence of electron-beam radiation on the micro-mechanical, thermo-mechanical, and structural properties of selected polymers. In the search for the desired improvement of polymers, it is possible to use, inter alia, one particular possible modification-Namely, crosslinking-Which is a process during which macromolecular chains start to connect to each other and, thus, create the spatial network in the structure. In the course of the treatment of the ionizing radiation, two actions can occur: crosslinking and scission of macromolecules, or degradation. Both these processes run in parallel. Using the crosslinking technology, standard and technical polymers can acquire the more "expensive" high-tech polymeric material properties and, thus, replace these materials in many applications. The polymers that were tested were selected from across the whole spectra of thermoplastics, ranging from commodity polymers, technical polymers, as well as high-performance polymers. These polymers were irradiated by different doses of beta radiation (33, 66, 99, 132, 165, and 198 kGy). The micro-mechanical and thermo-mechanical properties of these polymers were measured. When considering the results, it is obvious that irradiation acts on each polymer differently but, always when the optimal dose was found, the mechanical properties increased by up to 36%. The changes of micro-mechanical and thermo-mechanical properties were confirmed by structural measurement when the change of the micro-hardness and modulus corresponded to the crystalline phase change as determined by X-ray and gel content.
2013 8TH INTERNATIONAL SYMPOSIUM ON ADVANCED TOPICS IN ELECTRICAL ENGINEERING (ATEE), 2013
The functional characteristics depend strongly on the chemical structure of polymer and on the formulation of material, as well. In the present work, the effects of gamma irradiation at different doses on the resistivity and on the absorption currents in nanocomposites of thermoplastic polymers, such as low density polyethylene (LDPE), polypropylene (PP) and ethylene-propylene-diene monomer rubber (EPDM) are analysed. The influences of the polymer structure as host matrix (LDPE, PP, EPDM) and nanoSiO 2 concentration (between 2 and 5 wt.%) on electrical features are discussed. A correlation between electrical and thermal properties is illustrated for all formulations.
Dose effect in gamma-irradiated polyethylene studied by positron annihilation lifetime technique
Radiation Physics and Chemistry, 1994
Positron annihilation spectroscopy, thermogravimetric and FT-IR techniques are used to study the effect of low doses of gamma irradiation on microscopic structure of cellulose triacetate films. The irradiation is done at room temperature with doses ranging from 5 to 25 kGy. The ortho-positronium lifetime component associated with the pick-off annihilation of positronium trapped by the free volume is analyzed. Alternation in the ortho-positronium lifetime is observed reaching to a minimum value at10 kGy which is followed by a sharp increase at 15 kGy. Afterward, the ortho-positronium lifetime remains almost constant up to 25 kGy. The intensity of ortho-positronium component, I 3 , revealed an opposite trend with respect to the ortho-positronium lifetime manner. The obtained results are discussed on the basis of free volume model. The thermogravimetric and FT-IR measurements bearded out the findings of positron annihilation spectroscopy and explained the variations on the CTA microstructure due to the effect of the low doses of gamma irradiation.