Thermo-oxidative degradation of isotactic polypropylene at high temperatures: phenolic antioxidants versus HAS

Gensler, R.; Plummer, C. J. G.; Kausch, H. H.; Kramer, E.J.; Pauquet, J. R.; Zweifel, Hans

doi:10.1016/s0141-3910(99)00113-5

Cited by 130 publications

(72 citation statements)

References 35 publications

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“…The most facile alternative for chemical resistance improvement is the addition of a suitable antioxidant. Several classes of antioxidants were intensively studied for various purposes: prevention of thermal degradation [6][7][8] or weather aging [9][10][11][12] , and radiation stability. [13][14][15] The majority of products reach high performances due to protective action of antioxidants, which confer excellent protection against the action of permanent Summary: The thermal stability of gamma irradiated low density polyethylene (LDPE) films in presence of various structures of hindered amine stabilizers (HAS) was investigated by the oxygen uptake method under constant temperature of 180 8C and normal pressure conditions.…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Zaharescu¹,

Kaci

Hebal

et al. 2004

Macro Materials & Eng

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Summary: The thermal stability of gamma irradiated low density polyethylene (LDPE) films in presence of various structures of hindered amine stabilizers (HAS) was investigated by the oxygen uptake method under constant temperature of 180 °C and normal pressure conditions. The thermo‐oxidation was run using air environment. The sigmoidal dependency of oxygen uptake allows the calculation of the main kinetic parameters: oxidation induction time and oxidation rate on the propagation step. The various steps involved in the thermal degradation process were detected by the derivative procedure applied to the dependencies of oxygen uptake on time. It was found that the kinetic parameters of the thermal degradation process, determined by oxygen uptake, revealed the antioxidant role of HAS in γ‐irradiated LDPE films by providing better stability, when compared with the unstabilized samples. Moreover, the results indicated that the dependencies of oxygen uptake on thermal degradation time involved two degradation stages: the former occurring in the ungrafted moiety and the latter taking place after the antioxidant depletion is achieved. The stabilization efficiency of these oxidation inhibitors provides satisfactory thermal resistance to LDPE films, especially those based on an alkoxyamine structure.Dependencies of oxygen uptake on time at the thermal degradation of LDPE irradiated at 812 kGy. (‐□‐) free of additive; (‐○‐) Tinuvin 123; (‐▵‐) Sanduvor PR 31; (‐⋄‐) Uvasil 299.magnified imageDependencies of oxygen uptake on time at the thermal degradation of LDPE irradiated at 812 kGy. (‐□‐) free of additive; (‐○‐) Tinuvin 123; (‐▵‐) Sanduvor PR 31; (‐⋄‐) Uvasil 299.

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Section: Introductionmentioning

confidence: 99%

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Zaharescu¹,

Kaci

Hebal

et al. 2004

Macro Materials & Eng

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“…The initial point of attack may be the tertiary carbon in propylene. 27,28 The data presented here indicate, however, that the rate of aging processes in HPEC is determined by the increased rate of oxygen diffusion and reactants mobility in polymers with higher EPR content. The higher proportion of the amorphous domains in HPEC1 in comparison to HPEC2, 6% versus 60%, and the corresponding higher amount of the EPR represented by the F component, 26 vs 21, 11 may also enhance the local reactivity.…”

Section: Degradation Of Hpec As a Function Of Epr Contentmentioning

confidence: 55%

“…In the case of samples prepared by injection molding of PP/EPR blends, depth-profiling studies have revealed the formation of a skin consisting of several layers ("stratification"), whose composition is different compared to the bulk phase 8,9,28 ; a transcrystalline layer (≈10 µm thick) followed by an elastomer region (≈20 µm thick) were detected in the outer regions of these samples. The resolution in the ESRI experiment is ≈100 µm; therefore, we cannot visualize these narrow regions.…”

Section: Effect Of Morphology On Thermal Degradationmentioning

confidence: 99%

Spatially resolved degradation in heterophasic polymers by ESR imaging and FTIR: The case of propylene-ethylene copolymers

Schlick

Kruczała

2005

J Coat. Technol. Res.

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Heterophasic propylene-ethylene copolymers (HPEC) containing bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770) as a hindered amine stabilizer (HAS) were thermally aged at 393 and 433 K. Two types of HPEC were examined, containing 25% and 10% ethylene (E), respectively, as ethylene/propylene rubber (EPR). Electron spin resonance (ESR) spectra of nitroxide radicals in HPEC were studied in the temperature range 100-433 K; the nitroxides were derived from the HAS and are termed HAS-NO. The results were compared with ESR spectra of the same radicals obtained first by oxidation of Tinuvin 770 and then were doped in HPEC and related homopolymers, polyethylene (PE) and polypropylene (PP); these nitroxides are termed "spin probes." ESR spectra indicated that HAS-NO and the spin probes reside in a range of amorphous sites differing in their dynamic properties. The relative population of the sites was explained by assuming that the crystalline domains exert a restraining effect on chains located in vicinal amorphous domains. Spatial and temporal effects of the aging process were studied by ESR and ESR imaging (ESRI) of HAS-derived nitroxide radicals, and by FTIR of films prepared by compression molding. 1D ESRI enabled the visualization of an outer region of thickness ≈100 µm that contained a lower amount of nitroxides, and is believed to result from the loss of the stabilizer by diffusion ("blooming") and possibly also in chemical reactions during aging. Two-dimensional spectral-spatial ESRI indicated the presence of nitroxide radicals in two amorphous sites, fast and slow; the corresponding relative intensity varied with sample depth. Both ESRI and FTIR experiments suggested a faster degradation rate in HPEC containing 25% E, as compared to 10% E; moreover, a larger Tinuvin 770 content in the polymers led to less efficient stabilization. FTIR spectra indicated increased ordering of polypropylene segments in HPEC during aging at 433 K.H eterophasic propylene-ethylene copolymers (HPEC) systems, known commercially as impact polypropylene copolymers (IPC), are an important class of polymers, due to their attractive mechanical properties and low cost. 1,2 The polymers consist of crystalline polypropylene (PP) modified by an elastomeric component, typically ethylene-propylene rubber (EPR), and are prepared by the polymerization of propylene in the presence of catalysts, and the sequential polymerization of a propylene-ethylene mixture with the same catalysts. 3 The resulting polymeric materials are heterophasic, but the specific morphology depends on the preparation method and monomer ratio. Many studies have demonstrated the presence of four phases in HPEC: crystalline PP, amorphous PP, crystalline EPR (mostly polyethylene, PE), and amorphous EPR. 4-7 The morphology of HPEC is of considerable interest because processing them at high temperatures can lead to morphological changes. Therefore, an understanding of the morphology and of the temperature dependence of domain size has enormous practical importance. For ...

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“…[29] The Molecular weight distributions (MWD) were determined using Polymer Laboratories PL-GPC220 High Temperature Gel Permeation Chromatograph. [5] Pentad distribution (mmmm content) was measured through 13 C { 1 H} NMR experiments on Bruker Avance-II 400 MHz NMR instrument. [30] Xylene soluble (II) was measured as per the standard ASTM method.…”

Section: Polymer Characterizationmentioning

confidence: 99%

“…The produced resin is, then, converted into stabilized polypropylene pellets through extrusion technology using different combination of additives for preventing thermal as well as non-thermal degradation, which is critical for end-use applications. [13] New developments in stabilization technology are focused on two directions. One approach involves the development of new and modified molecules based on synthetic [14][15][16][17] and naturally occurring [18] chemicals for better efficiency through extrusion mixing.…”

Section: Introductionmentioning

confidence: 99%

Stabilized polypropylene synthesis using supported titanium catalyst system in presence of phenolic compounds

Kothari

Makwana

Desai

et al. 2014

Designed Monomers and Polymers

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Stabilized polypropylene synthesis is carried out using supported titanium catalyst system in presence of phenols. The effect of phenolic compounds such as 2,2′-methylenebis(4-tert-butyl-6-methylphenol) (PH1) and 4,4′-methylenebis(2,6-di-tert-butylphenol) (PH2) is studied on the productivity and stereospecificity of catalyst system as well as on molecular weight characteristics. The extent of stabilization of PP resin by phenolic compounds for oxidative degradation is determined by measurement of oxygen induction time. Molecular weight and b color change are also investigated before and after thermal aging. The catalyst productivity was found to be unaffected by the concentration of phenolic compounds in the studied range. The thermal stability of the polymer resin is, however, found to be dependent on the nature of phenolic compound. The masked PH1 phenolic compound showed better antioxidant characteristic as compared to PH2.

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Thermo-oxidative degradation of isotactic polypropylene at high temperatures: phenolic antioxidants versus HAS

Cited by 130 publications

References 35 publications

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Spatially resolved degradation in heterophasic polymers by ESR imaging and FTIR: The case of propylene-ethylene copolymers

Stabilized polypropylene synthesis using supported titanium catalyst system in presence of phenolic compounds

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