Miscible polymer blend

There are, however, some miscible polyolefin blend systems. There is evidence of miscibility (sometimes limited) between various copolymers/terpolymers of ethylene with amorphous isotactic polypropylene [20 to 22]. These copolymers include ethylene-butene, ethylene-hexene and ethylene-octene copolymers  

Among hydrocarbon polydienes, there is miscibility between 1,2-polybutadiene and ds-1,4 polyisoprene [23] 

Polymer miscibility is most striking with polar polymers. There have been an especially large number of studies of the miscibility of poly(vinyl chloride) (PVC). Notable examples of miscible blends with PVC are aliphatic polyesters and their copolymers [24,25] 

Miscibility between halogenated polymers and aliphatic polyesters seems to be associated with hydrogen bonding interactions such as 

Other polar polymers also have wide ranges of miscibility with other polymers. An example is poly(vinylidene fluoride) (PVDF), 

Miscibility in polymer blends has been studied by both theoreticians and experimentalists. The number of polymer blend systems that have been found to be thermodynamically miscible has increased in the past 20 years. Systems have also been found to exhibit the upper or lower critical solution temperatures. So complete miscibility is found only in limited temperature and composition ranges. A large number of polymer pairs form two-phase blends. This is consistent with the small entropy of mixing that can be expected of high polymers. These blends are characterized by opacity, distinct glass transition temperatures, and deteriorated mechanical properties. Some two-phase blends have been made into composites with improved mechanical properties. Often, incompatibility is the general rule, and miscibility or even partial miscibility is the exception. 

Polycarbonate (PC) and aliphatic polyesters were found to form a miscible polymer blend. Kambour et al. [6] reported that copolymer of styrene and bromostyrene formed a miscible pair with copolymer of xylenyl and bromoxylenyl ether. 

Amoco [7] reported several polyaryl ether-sulfones to be miscible with each other. The miscible blend comprises a 1,4-arylene unit separated by ether oxygen and another resin 1,4 arylene separated by an SO2 radical. The miscible blends showed a single glass transition temperature in between the constituent values. The blend was transparent. These can be used for printing wiring board structures, electrical connectors, and other fabricated articles that require high heat and chemical resistance and good dimensional and hydrolytic stability. 

Differential scanning calorimetry (DSC) experiments indicated that atactic polystyrene and polyvinyl methyl ether (PVME) form miscible blends [8,9]. Syndiotactic and isotactic polystyrene when blended with PVME, phase separate at aU temperatures above the glass transition temperature of PVME. Only weak van der Waals interactions between the phenyl rings in polystyrene with the methoxy group of PVME were detected using 2-dimensional nuclear magnetic resonance (NMR) spectroscopy. 

and Barlow [10] found that an alpha-methylstyrene-acrylonitrile (AMS-AN) copolymer at 50 mole fraction AN formed miscible polymer blends with poly(methyl methacrylate) (PMMA) and with poly(ethyl methacrylate) (PEMA). AMS-AN copolymer did not form miscible blends with polyacrylates or polyvinyl acetate. The miscible blends were found to exhibit lower critical solution temperature (LCST) behavior. 

In general, the phase behavior and the morphological characteristics, as well as the crystallization process of blends of crystallizable polymers, depend on the composition, the chemical structure of the macromolecules, and their reciprocal interactions, that is, on the miscibility effects (in the melt and the amorphous solid phase). 

For miscible blends containing a crystallizable component, the overall Gibbs free energy change of the 

To analyze the crystallization behavior of crystalliz-able polymer blends, it is suitable to distinguish between systems containing only one crystallizable component (crystalline/amorphous blends) and those containing both crystallizable components (crystalline/crystalline blends). In all cases, the crystallization of a polymer blend will take place in a defined temperature range, between the values of the glass transition temperature, Tg, and the equilibrium melting temperature of the crys-taUisable polymer, below Tg the chain mobility is inhibited, while at temperatures near T° the crystal nucleation does not occur. 

For a binary miscible blend (A amorphous polymer, B crystalline polymer) the glass transition is intermediate between those of plain components (Tg, Tje) and thus the crystallization range—and the crystallization behavior— will depend on the glass transition of the amorphous component (Tja) (Fig. 10.2) [19]. In fact, if FgA is lower than T,b, the glass transition of the crystallizable polymer, the crystallization window of the blend (T°-Tg), where T° represents the equilibrium melting point of B in the blend, is larger than that of the neat crystallizable component (T b -TgB), and the ability to crystallize is enhanced. On the contrary, if TgA 

The effect of the amorphous component on the crystallization ability of the crystallizable polymer has been examined for some miscible blends. An improvement of poly( -caprolactone) (PCL) crystallization has been observed in blends with chlorinated polyethylene (CPE) [20], while for poly(ethylene oxide)/poly(ethyl methacrylate) (PEO/PEMA) [21], PCL/SAN [22], and poly(butylene therephthalate)/polyarylate (PBT/ PAr) [23] blends, the crystallization ability is markedly reduced. 

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Finally, similar effects can be seen in miscible polymer blends where the surface tension correlates with the enrichment of the lower-energy component at the surface as monitored by x-ray photoelectron spectroscopy [104],... 

Miscible Polymer Blends A subclass of polymer bends encompassing those blends that exhibit single-phase behavior. 

Partially Miscible Polymer Blends A subclass of polymer blends including those blends that exhibit a window of miscibility, i.e, they are miscible only at certain concentrations and temperatures. 

Fig. la —c. Schematic drawing of some specific examples of polymer molecules at an interface (a) the free surface of a homopolymer, (b) the surface enrichment of one component in a miscible polymer blend, and (c) the interface between polymers of different molecular weight and/or chemical composition... 

Randomisation in miscible polymer blends (formation of random copolymers). 

Miscible polymer blends, 20 318 barrier polymers, 3 398-399 Mishandling failure, 26 982 Mist... 

Simulation Study of Relaxation Processes in the Dynamical Fast Component of Miscible Polymer Blends. 

Most of the experiments reported so far have been performed on linear homopolymer systems. In Chap. 6 we discuss what has been achieved so far beyond such simple materials. We begin with the discussion of neutron spin echo data on miscible polymer blends, where the main issue is the dynamic miscibility . There are two questions Firstly, on what length and time scales and to what extent does a heterogeneous material like a blend exhibit homogeneous dynamics Secondly, how does it relate to the corresponding homopolymer properties ... 

In the future we will witness a drive towards more complexity. In this review, we have discussed a number of preliminary experiments pointing in this direction. In polymer blends, the question of dynamic mixing on a local scale was addressed and the Rouse dynamics in miscible polymer blends was studied. How the tube confinement evolves in blends where the two components have different tube diameters is a completely open question. Also, the question of how... 

Comparisons of the theory with experiment can not be presently made due to the lack of data on well characterized molecular IPN. Indications about its validity can, however, be deduced by examining its consistency at extreme cases of material behavior. The agreement at the one-component limit, for example, provided that the rubber is not very weak (iji not very small), has been successfully demonstrated by Ferry and coworkers [ ]. A useful result is obtained at the version of the theory applicable to the fluid state (i.e., at the limit of zero crosslinking). From the last two terms of Equation 13, the following relationship can be derived for the plateau [ ] and time dependent relaxation modulus of miscible polymer blends ... 

Note In polymers, because of the low mobility of polymer chains, particularly in a glassy state, metastable mixtures may exist for indefinite periods of time without phase separation. This has frequently led to confusion when metastable miscible polymer blends are erroneously claimed to be miscible. 

Polymeric material, exhibiting macroscopically uniform physical properties throughout its whole volume, that comprises a compatible polymer blend, a miscible polymer blend, or a multiphase copolymer. 

Table 2.8 Complementary Groups Found in Miscible Polymer Blends...

Table 4. Dimensionless self- and inter-association equilibrium constants values determined from miscible polymer blends scaled to a common reference volume (100 cm /mol) [83]...

Theoretically miscible polymer blends will show Tg values that are intermediate between those of the parent polymers. They follow such models as the Fox or Gordon-Taylor relationships (18,19). However, in the case of HPL/PVA blends, the Tg data did not follow any of these well known models, and Tg values above those of the parent polymers were observed (10). The quotient of the experimental blend-Ttf divided by the predicted (Fox) Tg consistently rose above 1.00 for blends exceeding 5% HPL content (10). This indicates molecular interactions between HPL and PVA. An... 

It has been shown that miscible polymer blends and copolymerization offer complementary routes to polymer systems of tailored properties. The recognition that miscibility (at least in a transient sense) is much more common with aromatic heterocyclic polymers than is observed with low temperature flexible... 

Fig. 2. Correlation of experimental values of the Langmuir capacity parameter (Sq) for C02 at 35 °C with the glass transition temperature of the polymer25) [cf. Eq. (10)]. Pure polymers (PSF = a poly-sulphone 231 COP = a copolyester 26) remaining abbreviations as in the text). Miscible polymer blends O PPO-PS 65> O PC-COP 26>...

J. A. Zawada, Component contributions to the dynamics of miscible polymer blends, Ph J). Thesis, Stanford University (1993). 

J. Zawada, C. Ylitalo, G. Fuller, R. Colby, and T. Long, Component relaxation dynamics in a miscible polymer blend Polyethylene oxide)/poly(methyl methacrylate), Macromolecules, 25,2896 (1992). 

Moskala EJ et al. (1984) On the role of intermolecular hydrogen bonding in miscible polymer blends. Macromolecules 17(9) 1671—1678... 

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