Mechanical and dielectric investigations of relaxations in polymers

Pechhold, W.; Sautter, E.; Soden, W. v.; Stoll, B.; Grossmann, H.P.

doi:10.1002/macp.1979.020031979114

Cited by 42 publications

(49 citation statements)

References 30 publications

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“…The T g s can be detected from the activation curves of Figure 7 by reading the temperatures corresponding to the dielectric relaxation frequencies. [26][27][28][29] The dielectric relaxation frequencies corresponding to the calorimetric T g s were found to be 0.006 Hz and 0.5 Hz for PMMA and PαMSAN, respectively. One can draw straight line between these two frequencies of the pure components which can inter- sect the other activation curves of the different composition at different frequencies.…”

Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

“…This method has been derived by considering that the distance along the logarithmic frequency (or time) scale in the activation diagram is nearly constant between the curves which were determined by different experimental methods. [26][27][28][29] The current method has been successfully used for detecting the dielectric T g s for some of plasticized polymers. 26 Extrapolation of the activation curves (to make the solid lines in Figure 7) can be done either by WLF-equation or more precisely by fitting f 0 , Q γ , Q s and 3r/d in the Meander model equation [27][28][29] …”

Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

“…This model was derived by considering the dislocation concept and described elsewhere. [27][28][29] One can fit this Meander model to the experimental activation curves using the non-linear regression technique. Table I represents the fitting parameters obtained from the regression.…”

Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

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Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Madbouly

2002

Polym J

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ABSTRACT:Blends of poly(methyl methacrylate), PMMA, and Poly(α-methyl styrene-co-acrylonitrile), PαMSAN, random copolymer have been studied by broadband dielectric relaxation spectroscopy and differential scanning calorimeter (DSC). The dielectric measurements were carried out over a wide range of frequency (10 −1 to 10 6 Hz) and temperature (30-155• C). The molecular dynamics of the glass relaxation process, α-process, was investigated as functions of composition, frequency and temperature. It has been found that, only one common α-relaxation process has been observed for all measured samples, its dynamics and broadness were found to be composition dependent. The existence of only one common α-relaxation process located at a temperature range between those of the pure polymer components was taking as a strong evidence for the miscibility of the blend over the entire range of composition. The miscibility was also confirmed by measuring the glass transition temperatures of the blends, T g s, calorimetrically using DSC and dielectrically from the activation curves of the α-relaxation processes of the blends. The T g s of the blends were found to follow Fox-equation. The composition dependence of the dielectric relaxation strength, ∆ε has been also examined for α and β-relaxation processes. In addition, the blending was found to have no effect on the kinetics and broadness of the β-relaxation processes of the PMMA, indicating that blending does not change the local environment of each component in the blend. This also led to in turn that the mixing of the two polymer components should take place on a structure level bigger than the segmental level to keep the local environment unchanged and small enough to have the same volume as the cooperative dipoles, which are related to the single T g of the miscible blend. KEY WORDS Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) (PMMA/ PαMSAN) / Miscibility / Molecular Dynamics / Physical or chemical combination of two structurally different polymers can be used to obtain materials with properties which differ from those of the constituent components and which can be optimized to meet specific needs, like chemical resistance, impact strength, flexibility or weatherability. The final properties of the blend depend on the properties of the pure polymer components, miscibility and adhesion between the phases as well as the size and uniformity of the phase texture or morphology. Many techniques have been extensively used to investigate the miscibility and molecular dynamics of polymer blends, such as, differential scanning calorimetry (DSC), 1, 2 NMR, 3-6 dielectric spectroscopy, 7-12 and mechanical measurements. [13][14][15][16][17] The dielectric relaxation spectroscopy is a powerful tool cable of providing information about the molecular dynamics and the nature of the interactions in blends by monitoring the motion of dipolar groups attached to molecular chains. The dielectric spectroscopy has been widely used in polymer relaxation analysis and has the advan...

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Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

Section: Pmma/pαmsan Blendsmentioning

confidence: 99%

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Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Madbouly

2002

Polym J

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“…Moreover, the plastic deformation within the 'crystal-0 lite ensemble' is assumed to be strongly related to global processes running within the 'short chain network' which is constituted by crystallites themselves. Figure 6, where hi is the relative weight of the i-th internal process should be originated by a broad size distribution of cooperatively jointed molecular aggregates up to large micro-blocks [69,40]. The largest number of the mechanism has according to the spectrum a mean relaxation time of about 100 sec.…”

Section: The Crystal Networkmentioning

confidence: 99%

Irreversible deformation of semicrystalline PUR-elastomers —a novel concept

Enderle

Kilian

Heise

et al. 1986

Colloid & Polymer Sci

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A description of irreversible quasi-isothermal deformation of PUR-elastomers to large strains is developed on the basis of the classical thermodynamics of irreversible processes. This approach is shown by representing stress-strain cycles at different constant strain rates and at two temperatures.The discussion implicates the description of birefringence data and first stretchingcalorimetric results.

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“…It is surprising to find in the literature that, regardless of the model used in calculation and its basic assumption, the domain length responsible for the glass transition process is of the order of 10-15 nm. 13,[16][17][18][19][20] According to this value, the concentration of the segments that experience a different local environment through blending will be less than lo%, since the interchain distance of PS is about 8.7f$18 i.e. this domain length is large enough to maintain the local environment of segments unchanged.…”

Section: 01mentioning

confidence: 99%

Dielectric Investigation of Molecular Dynamics of Blends: III. Effect of Molecular Weight in TMPC/PS Blends

1996

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Dielectric and calorimetric measurements have been carried out for tetramethyl polycarbonate/polystyrene (TMPC/PS) blends with different compositions. The effect of varying the molecular weight of the weakly polar component (PS) on the molecular dynamics of the polar segments of TMPC has been thoroughly studied over wide ranges of frequency (10−2−105 Hz), temperature (50–220°C) and number average molecular weight, M̄n, (6500–560 000 g mol−1). All blends were found to be compatible regardless of the composition ratio and the molecular weight of PS. Some new and interesting experimental findings have been observed concerning the effect of molecular weight on the glass temperature and on the broadness of the glass transition and relaxation. Neither the kinetics nor the distribution of relaxation times of the local process observed in pure TMPC was affected by blending with PS, regardless of the composition ratio or the molecular weight of PS. It has been concluded that the mixing of the polymeric components to form a homogeneous single phase (compatible blend) does not take place on a segmental level but on a structural one. The size of this structural level has been suggested to have the same volume as the cooperative dipoles, which is assumed to be the minimum volume responsible for a uniform glass transition (10–15 nm). The molecular weight dependence of the relaxation characteristics of the glass process and temperature could be attributed to the variation in the size and packing of the structural units.

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Mechanical and dielectric investigations of relaxations in polymers

Cited by 42 publications

References 30 publications

Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Broadband Dielectric Spectroscopy for Poly(methyl methacrylate)/Poly(α-methyl styrene-co-acrylonitrile) Blend

Irreversible deformation of semicrystalline PUR-elastomers —a novel concept

Dielectric Investigation of Molecular Dynamics of Blends: III. Effect of Molecular Weight in TMPC/PS Blends

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