Radiation induced oxidation of isotactic polypropylene and mechanism of action of HALS stabilizers

Faucitano, A.; Buttafava, A.; Mongini, G.; Martinotti, F.; Berzero, A.; Strada, L.

doi:10.1016/0969-806x(96)00024-2

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…It is generally accepted that the decomposition of polymers initiated by ionizing radiation proceeds comparably to UV‐induced degradation, i.e., via free radical mechanism 4. The efficiency of HAS additives depends on their molecular weight, structure, solubility and concentration in the polymer matrix 5. Conversion of amines into nitroxyl radicals following the reaction with peroxyl radicals leads to relatively stable intermediate species 6.…”

Section: Introductionmentioning

confidence: 99%

Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Aquino¹,

Araújo²

2008

J of Applied Polymer Sci

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Commercial Poly(methyl methacrylate) (PMMA) containing Tinuvin 622, a Hindered Amine Stabilizer (HAS), in 0.3% (wt/wt) concentration was investigated. The samples were irradiated with gamma radiation ( 60 Co) at room temperature in air. The viscosity-average molecular weight (M v ) was analyzed by viscosity technique. Both control PMMA (without HAS) and PMMA 1 622 (with HAS) showed a decrease in molecular weight with the increase in dose, reflecting the random scissions that occurred in the main chain. The G value (scissions/ 100 eV of energy transferred to the system) was also obtained by viscosity analysis. G value results showed that the addition of Tinuvin 622 into the PMMA matrix significantly decreased the number of scissions/100 eV at dose range of 0-60 kGy. Analysis of infrared spectra showed a decrease in the carbonyl index (CI) in irradiated samples.However the CI decrease was found lower for PMMA 1 622 than for control PMMA sample. Thermogravimetric analysis (TGA) revealed that maximum decomposition temperature of additive PMMA is 428C higher than control PMMA for unirradiated system. On the other hand this difference is not significant in irradiated systems at 60-kGy irradiation dose. The activation energy of the thermal degradation of PMMA was 165 kJ/mol, this activation energy increased 60 kJ/mol when Tinuvin 622 was added to PMMA matrix. Therefore Tinuvin 622 is a suitable radiostabilizing agent for commercial PMMA in a 0-60 kGy dose interval.

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Section: Introductionmentioning

confidence: 99%

Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Aquino¹,

Araújo²

2008

J of Applied Polymer Sci

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“…Otuda, ukoliko treba da potisnemo kidanje, potreban je efikasan umreživač [16][17][18][19]. Protektivni i umrežavajući efekat antioksidanasa i čistača radikala na PP i efekti zračenja na efikasnost antioksidanasa u ovom polimeru je uočena od strane više autora [10,13,[16][17][18][19][20][21][22][23]. U najvećem broju slučajeva doza potrebna za sterilizaciju je oko 25 kGy.…”

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Properties of isotactic polypropylene irradiated in various atmospheres

Miličević¹,

Suljovrujić²

2010

Hem Ind

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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 δ) 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 (δ and γ) relaxations with gamma radiation confirmed great sensitivity of iPP structure to radiation-induced changes. Complete “vanishing” of the γ 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

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The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation

Suljovrujić

2009

European Polymer Journal

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Radiation induced oxidation of isotactic polypropylene and mechanism of action of HALS stabilizers

Cited by 5 publications

References 2 publications

Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Properties of isotactic polypropylene irradiated in various atmospheres

The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation

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