Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. I. Electron spin resonance spectra

Varghese, Biji; Schlick, Shulamith

doi:10.1002/polb.10109

Cited by 19 publications

(24 citation statements)

References 23 publications

(30 reference statements)

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“…For this reason, our initial objective was to study spatial effects in the degradation of HPEC containing a hindered amine stabilizer (HAS), with methods developed and used in our study of degradation in UV-irradiated and heat-treated poly(acrylonitrile-butadiene-styrene) (ABS) containing HAS: 15 The major method of study was 1D and 2D electron spin resonance imaging (ESRI) based on the formation of nitroxide radicals from the HAS during aging. Deductions from the ESRI experiments were supported by the spin probe study of ABS and related polymers 16 and by attenuated total reflectance (ATR) FTIR spectra of microtomed layers (50 µm thick) of the polymer. 17 Our expectation was that the clear connection between phase heterogeneity and degradation, which was key to the interpretation of the results in ABS, would also be applicable to the HPEC system.…”

Section: Introductionmentioning

confidence: 99%

Thermal Aging of Heterophasic Propylene−Ethylene Copolymers: Morphological Aspects Based on ESR, FTIR, and DSC

et al. 2003

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Electron spin resonance (ESR) spectra of nitroxide radicals formed in thermally treated heterophasic propylene−ethylene copolymers (HPEC) containing bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770) as a hindered amine stabilizer (HAS) were studied in the temperature range 100−433 K; the nitroxides are 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 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 in HPEC and homopolymers reside in a range of amorphous sites differing in their dynamical properties. Evidence for the various sites was obtained from the ESR line widths, the temperature variation of the extreme separation in the ESR spectra, and the effect of stress on the ratio of the fast and slow components in the spectra of HAS−NO in thermally treated HPEC. The relative population of sites was explained by assuming that the crystalline domains exert a restraining effect on chains located in vicinal amorphous domains; in PE the restraining effect was more pronounced in the polymer with the higher crystallinity (HDPE vs LDPE). Additional support for this assumption was provided by Fourier transform infrared (FTIR) spectra of HPEC and related polymers and by differential scanning calorimetry (DSC). The dynamically restrained chains evidenced by the spin probes are thought to be located in a rigid amorphous phase, which was described in the literature. In HPEC the fast spectral component represents unrestrained ethylene−propylene rubber (EPR) chains, and the slow spectral component represents amorphous PP and EPR chains in the rigid amorphous phase. This study has demonstrated the exceptional sensitivity of ESR spectra from nitroxide radicals to polymer morphology and degree of crystallinity.

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Section: Introductionmentioning

confidence: 99%

Thermal Aging of Heterophasic Propylene−Ethylene Copolymers: Morphological Aspects Based on ESR, FTIR, and DSC

et al. 2003

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“…Polymers doped with nitroxide spin probes are usually prepared by the dissolution method, which involves solubilization of the polymer and probe in the solvent, followed by solvent evaporation. This was the method used in the case of ABS polymers doped with spin probes . Dissolution of HPEC1 and HPEC2 can be achieved in xylene at ≈400 K, but the process is slow and sometimes incomplete.…”

Section: Methodsmentioning

confidence: 99%

“…This was the method used in the case of ABS polymers doped with spin probes. 32 Dissolution of HPEC1 and HPEC2 can be achieved in xylene at ≈400 K, but the process is slow and sometimes incomplete. For this reason, in this study the polymers were doped with the nitroxides by the melting method: Weighed amounts of the radical and polymer were mixed slightly above the melting point of the polymer.…”

Section: Methodsmentioning

confidence: 99%

Measuring Diffusion Coefficients of Nitroxide Radicals in Heterophasic Propylene−Ethylene Copolymers by Electron Spin Resonance Imaging

Kruczała

Schlick

2010

Macromolecules

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Heterophasic propylene-ethylene copolymers (HPECs), also known as impact-modified polypropylene copolymers (IPC), are an important class of materials because of their attractive mechanical properties and low cost. Their chemical composition and phase heterogeneity have important effects on the physical and mechanical properties of these systems. Commercially used HPECs usually contain stabilizers such as hindered amines, which can be lost by diffusion (blooming). We present the measurement of the diffusion coefficient of nitroxide radicals by electron spin resonance imaging (ESRI); the radicals were obtained by oxidation of the commercial Tinuvin 770 hindered amine stabilizer (HAS) with m-chloroperoxybenzoic acid and consist of a mixture of mono-and biradicals. The diffusion rates were measured in two polymers, HPEC1 and HPEC2, which differed in the ethylene (E) to propylene (P) ratio, 25:75 and 10:90 wt %, respectively. One dimensional (1D) ESRI allowed the visualization of the radical distribution ("profiles") within the sample as a function of storing time at 393 K. Simulation of this distribution led to the determination of the macroscopic diffusion coefficients, D, of the paramagnetic tracer in HPEC1 and HPEC2. The results indicate that the main factor determining the diffusion rates in these polymers is the amount of the crystalline phase, mostly composed of isotactic polypropylene (iPP). The D value was the same within experimental error in both systems, 1.42 Â 10 -8 cm 2 s -1 . Comparison with literature data of the temperature variation of D for the same diffusant in polyethylene (PE) and polypropylene (PP) suggest that in both HPEC1 and HPEC2 the diffusion takes place in the amorphous phase restrained by the proximity of the crystalline domains. The results also indicate that ≈20% of the diffusant is lost by evaporation ("blooming"). Results of spectral-spatial 2D ESRI show that the ESR spectra of the nitroxides do not change significantly along the sample length during diffusion, suggesting that the loss of stabilizer is due to diffusion and not to chemical reactions.

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“…In the spectra of nitroxyl radical XVII in all homopolymers, as well as in the copolymers SAN and SB, only one motional component was detected. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene-rich domains (the fast component) and SAN-rich domains (the slow component) (Figure 14.13) [49,50].…”

Section: Copolymersmentioning

confidence: 99%

ESR Spectroscopy of Multiphase Polymer Systems

Valić

Andreis

Klepac

2011

Handbook of Multiphase Polymer Systems

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Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. I. Electron spin resonance spectra

Cited by 19 publications

References 23 publications

Thermal Aging of Heterophasic Propylene−Ethylene Copolymers: Morphological Aspects Based on ESR, FTIR, and DSC

Thermal Aging of Heterophasic Propylene−Ethylene Copolymers: Morphological Aspects Based on ESR, FTIR, and DSC

Measuring Diffusion Coefficients of Nitroxide Radicals in Heterophasic Propylene−Ethylene Copolymers by Electron Spin Resonance Imaging

ESR Spectroscopy of Multiphase Polymer Systems

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