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

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.

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.

Gold nanoparticles (GNP) induced redox modulation in organoselenium compounds: distinction between cyclic vs. linear structures

RSC Advances ◽  
2016 ◽  
Vol 6 (73) ◽  
pp. 69501-69508
Author(s):  
Pavitra V. Kumar ◽  
Beena G. Singh ◽  
Anand Ballal ◽  
Vimal K. Jain ◽  
Michio Iwaoka ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Oxidative Degradation ◽  
Linear Structures ◽  
Organoselenium Compounds ◽  
Redox Modulation ◽  
Redox Behaviour ◽  
Radiation Induced

Structure of organoselenium compounds affects their binding with gold nanoparticles and modulates their redox behaviour and radiation induced oxidative degradation.

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