scholarly journals Properties of isotactic polypropylene irradiated in various atmospheres

2010 ◽  
Vol 64 (3) ◽  
pp. 201-208 ◽  
Author(s):  
Dejan Milicevic ◽  
Edin Suljovrujic
Keyword(s):  
Low Temperature ◽  
Ir Spectroscopy ◽  
Gamma Irradiation ◽  
Isotactic Polypropylene ◽  
Oxidative Degradation ◽  
Gel Point ◽  
Dielectric Losses ◽  
Dielectric Relaxations ◽  
Radiation Induced ◽  
Induced Changes

In this paper, changes in structure and physical properties of stabilized isotactic polypropylene (iPP) were created by gamma irradiation, up to a dose of 700 kGy, in different media: air, deionized distilled (DD) water and acetylene. Two main effects occur when polyolefins, such as iPP, are subjected to ionizing radiation: crosslinking and scission of macromolecules. The domination of one or the other of these competitive processes is determined by both the structural peculiarities of the polymers and the experimental irradiation conditions. Gel and infrared (IR) spectroscopy measurements were used to determine the changes in the degree of network formation and oxidative degradation, respectively. Sol-gel analysis was studied in detail using the Charlesby-Pinner (C-P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan ?) analysis in a wide temperature and/or frequency range. Evolution of low temperature dielectric relaxations with gamma irradiation was investigated. The results showed that degradation was the major reaction in the initial step of irradiation, no matter what the atmosphere was. The C-P equation seemed applicable when stabilized iPP was irradiated within a certain dose range in various atmospheres. The iPP irradiated in acetylene/air had the lowest/highest values for oxidation level, dielectric losses, Dg and G(s)/G(x) values. The calculated Dg values are 1.5 and 5 times larger for the irradiation in DD water and air than for the acetylene. Furthermore, our data confirm that oxidation strongly affects the gel point but has a much lower effect on the G(S)/G(X) ratio. In the case of dielectric relaxation measurements, the connection between the oxidative degradation and dielectric properties is well established and is in good agreement with IR spectroscopy measurements. The amount of carbonyl, hydroperoxide and other polar groups is much higher for the irradiation in air than in other media, leading to higher dielectric losses. Disappearance of low temperature (? and ?) relaxations with gamma radiation confirmed great sensitivity of iPP structure to radiation-induced changes. Complete ?vanishing? of the ? relaxation in iPP samples irradiated in air is connected with a large radiation-induced oxidative degradation in this medium. Similar crosslinking, oxidation and dielectric behaviour was observed for the samples irradiated in water and acetylene, indicating DD water as a good crosslinking medium.

scholarly journals Modification of ethylene-norbornene copolymer by Gamma irradiation

2006 ◽  
Vol 60 (11-12) ◽  
pp. 311-315 ◽  
Author(s):  
Zorica Kacarevic-Popovic ◽  
Bojana Secerov ◽  
Milena Marinovic-Cincovic ◽  
Zoran Nedic ◽  
Slobodan Jovanovic
Keyword(s):  
Gamma Irradiation ◽  
Radiation Chemistry ◽  
High Energy ◽  
Spectrophotometric Analysis ◽  
New Combination ◽  
Polymeric Systems ◽  
New Class ◽  
Radiation Induced ◽  
Dsc Method ◽  
Induced Changes

The possibility of modifying polyethylene and many other polymers with high energy radiation has led to many useful applications. Due to their new combination of properties and the shortage of experimental data, the radiolysis of a new class of materials, cyclo-olefin copolymers (COC), polymerised from norbornene and ethylene using metallocene catalysts, is of great interest to the study of radiation chemistry and the physics of polymeric systems. Ethylenenorbornene copolymer, pristine and containing an antioxidant were subjected to gamma irradiation in the presence of air and in water. The irradiated copolymer was studied using IR and UV-vis spectrophotometric analysis. The radiation-induced changes in the molecular structure were correlated to changes in the glass transition temperature measured by the DSC method.

Radiation-induced changes in the structure of polypropylene

1959 ◽  
Vol 253 (1274) ◽  
pp. 322-330 ◽  
Keyword(s):  
Main Chain ◽  
High Energy ◽  
Theoretical Expression ◽  
Cross Linking ◽  
Gel Point ◽  
High Energy Radiation ◽  
Infra Red ◽  
Radiation Induced ◽  
Induced Changes ◽  
Good Agreement

Polypropylene undergoes both cross-linking and random main-chain fracture when exposed to high-energy radiation, the ratio of cross-linking to chain fracture varying with the dose received up to the gel point. An examination of the infra-red absorption spectrum of the irradiated polymer has shown that, in addition, vinylidine unsaturation ( R . R' /C=CH 2 ) is formed in the ratio of one vinylidene double bond to each chain fracture. The rate of main-chain fracture deduced from intrinsic viscosity measurements has been found to be initially (up to a dose of 35 Mrad) a function of the number of chain fractures produced, rather than proportional to the intensity of the radiation, as might have been expected from the behaviour of other polymers. After a dose of 50 to 60 Mrad an insoluble cross-linked gel can be separated from the polymer by solvent extraction, and the sol fraction decreases on further irradiation in accordance with the theoretical expression derived by Charlesby (1953), assuming that for every cross-link formed, one bond between two monomer units is broken. A mechanism for the radiation-induced changes is proposed, based upon the application of classical chemical kinetics, which is in good agreement with the observed phenomena.

Radiation-induced oxidative degradation of isotactic polypropylene

1981 ◽  
Vol 26 (4) ◽  
pp. 1361-1372 ◽  
Author(s):  
El-Sayed A. Hegazy ◽  
Tadao Seguchi ◽  
Kazuo Arakawa ◽  
Sueo Machi
Keyword(s):  
Isotactic Polypropylene ◽  
Oxidative Degradation ◽  
Radiation Induced

Radiation induced changes in low-temperature oxide mos structures (Al-Si02Si)

1982 ◽  
Vol 62 (1-2) ◽  
pp. 1-5 ◽  
Author(s):  
V. G. Litovchenko ◽  
V. Ya. Kiblick ◽  
S. S. Georgiev ◽  
K. I. Kirov
Keyword(s):  
Low Temperature ◽  
Radiation Induced ◽  
Temperature Oxide ◽  
Induced Changes ◽  
Mos Structures

scholarly journals Influence of the irradiation conditions on the effect of radiation on polyethylene

2004 ◽  
Vol 69 (12) ◽  
pp. 1029-1041 ◽  
Author(s):  
Zorica Kacarevic-Popovic ◽  
Dusan Kostoski ◽  
Ljiljana Novakovic ◽  
Nada Miljevic ◽  
Bojana Secerov
Keyword(s):  
Molecular Structure ◽  
Oxidative Degradation ◽  
Spectrophotometric Analysis ◽  
Low Density Polyethylene ◽  
Structure Evolution ◽  
Low Density ◽  
Double Bonds ◽  
Radiation Induced ◽  
Induced Changes ◽  
Evolution Of Oxygen

Two types of polyethylene, low density (LDPE) and high density (HDPE), as well as low density polyethylene containing an antioxidant were subjected to ?-irradiation in the presence of air and in water. The irradiated polymers were studied using IR spectrophotometric analysis. The radiation induced oxidative degradation was followed through the formation of oxygen containing groups by the development of bands in the 1850?1650 cm-1 region and double bonds formation by the development of bands in the 1050?850 cm-1 region. The crosslinking efficiency was determined by measuring the gel content by extraction with xylene. The radiation induced changes in the molecular structure, evolution of oxygen containing species and formation, of vinyl double bonds as well as of the crosslinking efficiency are discussed in terms of the properties of the polymers in an electric field of low strength.

Radiation Induced Graft Copolymerization of Vinyl Acetate and Isopropenyl Acetate Onto Isotactic Polypropylene

1996 ◽  
Vol 61 (2) ◽  
pp. 259-267 ◽  
Author(s):  
Bhupendra N. Misra ◽  
G. S. Chauhan ◽  
Inderjeet Kaur
Keyword(s):  
Vinyl Acetate ◽  
Isotactic Polypropylene ◽  
Graft Copolymerization ◽  
Optimum Conditions ◽  
Reaction Parameters ◽  
Maximum Percentage ◽  
Radiation Induced ◽  
Isopropenyl Acetate

Radiation-induced graft copolymerization of vinyl acetate (VAC) and isopropenyl acetate (PAC) onto isotactic polypropylene (IPP) has been studied. The percentage of grafting was calculated for various reaction parameters, and the optimum conditions for attaining the maximum percentage of grafting were determined. Maximal achieved extents of grafting are 39% and 29% for VAC and PAC, respectively. The reactivity of the two monomers with respect to grafting is discussed.

Sign in / Sign up

Export Citation Format

Share Document