Dynamic mechanical properties of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐polystyrene blends
01 May 1970-Polymer Engineering and Science (Society of Plastics Engineers, Inc.)-Vol. 10, Iss: 3, pp 133-138
TL;DR: In this article, a mixture of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) has been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments.
Abstract: Blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) have been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments. Three different compositions were studied by the dynamic mechanical and DSC techniques. The weight fractions of PPO in the mixtures were 0.25, 0.50 and 0.75. The dynamic mechanical measurements indicate that partial mixing took place but that two distinct phases, one rich in PS and the other in PPO, exist in all the mixtures studied. Each phase exhibits a characteristic relaxation peak associated with the glass transition of that phase. DSC measurements, on the other hand, reveal only a single glass transition apparently characteristic of the PS rich phase in each case. The results indicate that a given type of experiment will indicate compatibility or incompatibility depending upon the size of the molecular process it represents.
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TL;DR: In this paper, a self-concentration φ is estimated by assigning a length scale (or volume) to a particular dynamic mode, and then the relevant self-consistency φs can be estimated.
Abstract: In a miscible polymer blend the local environment of a monomer of type A will, on average, be rich in A compared to the bulk composition, φ, and similarly for B; this is a direct consequence of chain connectivity. As a result, the local dynamics of the two chains may exhibit different dependences on temperature and overall composition. By assigning a length scale (or volume) to particular dynamic mode, the relevant “self-concentration” φs can be estimated. For example, we associate the Kuhn length of the chain, lK, with the monomeric friction factor, ζ, and thus the composition and temperature dependences of ζ should be influenced by φs calculated for a volume V ∼ lK3. An effective local composition, φeff, can then be calculated from φs and φ. As lower Tg polymers are generally more flexible, the associated φ s is larger, and the local dynamics in the mixture may be quite similar to the pure material. The higher Tg component, on the other hand, may have a smaller φs, and thus its dynamics in the mixture w...
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01 Jan 1980
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TL;DR: In this article, a general guide to polymer miscibility is presented, which is based on a simple balance between unfavourable physical forces, described in terms of non-hydrogen bonded solubility parameters, and favorable specific interactions.
272 citations
TL;DR: In this article, a calorimetric study was carried out on blends of poly(vinylidene fluoride) (PVF 2 ), and isotactic, atactic and syndiotactic poly(methyl methacrylate) (i-, a-, and s-PMMA).
200 citations
TL;DR: In this paper, the authors used differential scanning calorimetry to examine blends of poly(ethylene oxide) (PEO), Mn = 300 g/mol, and a poly(methylmethacrylate) (PMMA) (n = 10,000 g/m) across the complete composition range.
Abstract: Differential scanning calorimetry has been used to examine blends of a poly(ethylene oxide) (PEO), Mn = 300 g/mol, and a poly(methylmethacrylate) (PMMA), Mn = 10,000 g/mol, across the complete composition range. The relatively low molar mass of the PEO minimizes interference from crystallization. In the midrange of composition, ∼25–70% PEO, two broad, but distinct, glass transitions are resolved. These are interpreted as distinct glass transitions of the two components, as anticipated by the self-concentration model of Lodge and McLeish. The composition dependence of the observed transitions is well described by the self-concentration approach, using lengthscales of approximately two-thirds of the Kuhn length. The results are compared with previous measurements on PEO/PMMA blends and other miscible systems. The principal, general conclusion is that one should actually expect two glass transitions in a miscible polymer blend or polymer solution; the rule of thumb that two transitions indicate immiscibility is incorrect. Furthermore, attempts to rationalize two transitions on the basis of incomplete segmental mixing, or other unspecified “nanoheterogeneity,” may not be justified in many cases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 756–763, 2006
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TL;DR: The Gordon-Taylor equation relating the glass transition temperature of a copolymer to glass transition temperatures of the homopolymers is equivalent to a linear plot as discussed by the authors, where c1 and c2 are the weight fractions of the constituents and A1 and A2 are constants.
Abstract: The Gordon-Taylor equation relating the glass transition temperature θ of a copolymer to the glass transition temperatures θ1 and θ2 of the homopolymers is equivalent to
where c1 and c2 are the weight fractions of the constituents and A1 and A2 are constants. It can be recast into the following forms suitable for linear plots
and
where k = A2/A1. Data from the literature on 10 copolymer systems, including butaciene-styrene copolymers, give linear plots, verifying the equation within experimental error. However, the observed value of k is in most cases significantly smaller than the ratio of the differences of the volume-temperature coefficients for each homopolymer in the rubbery and glassy states, as required by the derivation of Gordon and Taylor. The glass transition temperature (in °C.) for a butadiene-styrene copolymer prepared by emulsion polymerization at 50°C. may be calculated from the weight fraction c2 of bound styrene as
and for a similar 5° copolymer as
306 citations
TL;DR: In this article, sound velocity, v, and damping factor were determined in poly(2.6-dimethyl-1.4-phenylene oxide) over a wide range of temperature (from 80 to 500°K) at acoustic frequencies.
Abstract: Dynamic mechanical properties (sound velocity, v, and damping factor, Q−1) have been determined in poly(2.6-dimethyl-1.4-phenylene oxide) over a wide range of temperature (from 80 to 500°K) at acoustic frequencies.
The examined polymer exhibits two mechanical relaxation effects, one, α, at temperatures above 480°K, characterized by a sudden strong drop of the elastic modulus and by a rapid increase of the damping factor with increasing temperature, and another, β, below the glass transition point, Tg, characterized by a small drop of the elastic modulus, between 290 and 370°K, and by a damping maximum at about 370K (fm = frequency corresponding to the maximum ⋍ 7000 Hz).
The α relaxation effect has been attributed to the thermal excitation of cooperative motions in the chain, while the secondary β relaxation has been interpreted as due to oscillation of aromatic rings around COC bond. The damping maximum, for the lateer, is shifted toward higher temperatures with increasing frequency, following an ARRHENIUS-type equation with an apparent activation energy of about 20 kcal/mole.
Die dynamischen Eigenschaften von Poly(2.6-dimethyl-1.4-phenylenoxid) wurden im akustischen Bereich und im Bereich langsamer Ultraschallfrequenzen untersucht. Diese Untersuchungen wurden mit einer elektrostatischen Methode (Biegeschwingung) bei Temperaturen von 80° bis 500°K durchgefuhrt.
Das Polymere zeigt zwei mechanische Relaxationseffekte, den ersten, „α”, bei Temperaturen uber der Glas-Temperatur, den zweiten, „β”, bei tieferen Temperaturen, im glasartigen Zustand. Der α-Prozes steht in Zusammenhang mit der thermischen Aktivierung der Bewegungen in der Kette, wahrend der β-Prozes mit der oszillatorischen Rotation in den Ringen zusammenhangt. Das β-Dampfungsmaximum verschiebt sich mit steigender Frequenz nach hoheren Temperaturen. Aus der Neigung der Kurve von log fm−1/T ergibt sich ein Wert der Aktivierungsenergie ⋍ 20 kcal/Mol.
24 citations