Comparison of the mechanical properties of styrene-based ionomers containing either crown ether or pentaethylene glycol with those of underneutralized ionomers
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Dynamic mechanical properties of styrene-based ionomers containing varying amounts of either 15-crown-5 ether (CE) or pentaethylene glycol (PG) are compared with those of ionomers of varying degree of neutralization (ND). The cluster Tg (Tg,c) and ionic modulus of the ionomers decrease with increasing amount of CE or PG or decreasing ND. Thus, we propose that the CE binds Na+ strongly to form a large-sized complex. Thus, the electrostatic interactions between charges decrease, leading to lower Tg,c. For the PG-containing ionomers, the PG acts as polar plasticizer, further lowing the Tg,c. In the case of the underneutralized ionomers, the Tg,c is reduced by the existence of both relatively weak hydrogen bonds between carboxylic acid groups and relatively strong ionic bonds between ion pairs in the multiplets. The small-angle X-ray scattering results are also supportive of the above interpretations. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1358–1367Keywords:
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Sodium and zinc salts of poly(ethyaene-co-methacrylic acid) ionomers consist of three phases, i.e. ionic aggregates, amorphous, and crystalline phases. Dye molecules after soaked from the methanol solution are located near the amorphous phase or ionic aggregates within ionomer films. Depending on the location of the molecules in the ionomer film, they are under influence of dispersion forces (ethylene parts), polar forces (acid parts). and ionic dipole (ionic aggregates) interactions. The UV/Vis absorption peak of Nile Red under the dispersion force is found at near 500 nm, for the dye under the polar force effect 525 nm, and 550 and 610 nm for the dyes under and ionization effects, respectively. Since the divalent ion has larger ionic dipole than the monovalent ion, the larger red-shift of the absorption band due to the ionic dipole interaction is observed for counter ion.
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This paper reviews the current trends in replacing commonly used plasticizers in poly(vinyl chloride), PVC, formulations by new compounds with reduced migration, leading to the enhancement in mechanical properties and better plasticizing efficiency. Novel plasticizers have been divided into three groups depending on the replacement strategy, i.e., total replacement, partial replacement, and internal plasticizers. Chemical and physical properties of PVC formulations containing a wide range of plasticizers have been compared, allowing observance of the improvements in polymer performance in comparison to PVC plasticized with conventionally applied bis(2-ethylhexyl) phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) terephthalate and di-n-octyl terephthalate. Among a variety of newly developed plasticizers, we have indicated those presenting excellent migration resistance and advantageous mechanical properties, as well as those derived from natural sources. A separate chapter has been dedicated to the description of a synergistic effect of a mixture of two plasticizers, primary and secondary, that benefits in migration suppression when secondary plasticizer is added to PVC blend.
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In this paper,the migration of three kinds of plasticizers(terephthalate,citrate,phthalate) in flexible crosslinked PVC was studied in 40℃ olive oil.The results show that the migration ratio increases with time,and increases quickly in initial 24 h,and then tends to be gently after 192 h,which can be attributed to two reasons.The first,concentration gradient of plasticizers between the samples and solution is high at beginning,it is propitious to migration.The second,crosslinked net which is formed by peroxide is located at the inner of PVC sample and can?t inhibit the migration of the plasticizers located at the edge of the sample,which consequently migrate quickly into solution in initial stage.As the soak time increasing,the concentration gradient of plasticizers between sample and solution is reduced.Moreover,crosslink structure of PVC could effectively inhibit the migration of plasticizers,and the higher gel content the sample has,the more effective inhibition it shows.The migration ratio can be reduced about 30% when the sample has the maximal gel content.In addition,the results reveal that the migration ratio of plasticizers is ranged in the order of citrate,phthalate,terephthalate from large to small,which can be attributed to the difference of molecular structure of plasticizers.The higher molecular polarity the plasticizer has,the smaller migration ratio is shown in 40℃ olive oil environment.It was found that the effect of PVC crosslink on inhibiting the migration ratio among the three plasticizers has no obvious rule.
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A new criterion for evaluating different plasticizers the ability of suppression of the Β transition in plasticized PVC blends. Accordingly, the Β suppression ability is proportional to the PVC-plasticizer compatibility, expressed either by the critical solution temperature, CST, or by the interaction parameter related to the difference between the solubility parameters of the blend components. The criterion is, however, valid for low plasticizer contents (<5%w/w) only, as long as the Β transitions are not overlapped by the α transitions, shifted towards lower temperatures due to the effect of the plasticizer. For higher plasticizer contents the α transition starts to overlap the Β transition and the Β suppression ability of the plasticizer depends increasingly on the efficiency of the plasticizer i.e. on the depression of the glass transition temperature of PVC (related to theT g of the plasticizer). Accordingly, plasticizers with both good efficiency (lowT g) and compatibility are more effective in the Β suppression than plasticizers which have only a higher compatibility but also a highT g (i.e. reduced efficiency).
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The advance in synthesis and application of ionomer was reviewed in this paper. The morphology of ionomer is unique because of multiplets and ionic clusters formed by aggregation of ionic pairs. Morphology character of ionomer and principal factor such as nature of the host polymer, nature of ionic pairs, heat history, temperature etc. affecting morphology were studied. The models of morphology were also reviewed. The mechanics, dielectric and solution properties resulting from specific morphology were presented in this paper. The presence of multiplets and ionic clusters make ionomer better suited for some specific application, such as food package, insulation material, polymer improvement etc..
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Plasticizers improve polymer material flexibility and durability by lowering glass transition and cold flex temperatures. While many different classes of plasticizers have been synthesized and used in various applications, several classes have been phased out due to concerns over their safety. One of the main problems that hinder the development of a new generation of efficient and safe plasticizers is the plasticizers' migration and exudation from polymer materials, which leads to a reduction of mechanical properties and premature degradation. Here, we employed multiscale molecular dynamics, validated by experiment, to investigate the molecular mechanism of exudation of an orthophthalate plasticizer (di-2-ethylhexyl phthalate (DEHP)), non-orthophthalate plasticizers (di-n-butyl terephthalate (DnBT) and di-2-ethylhexyl terephthalate (DEHT)), and their blends from polyvinyl chloride (PVC). The results suggest that DnBT acted as an intermediary between PVC and DEHT, improving the compatibility of the plasticizer blend and reducing the degree of exudation. Specifically, it was predicted that the 70:30 wt % DnBT–DEHT blend was on par with the DEHP control system. These results also suggest that plasticizer-PVC compatibility is a stronger determinant of plasticizer exudation than the plasticizer size, diffusivity, and viscosity, given that DnBT is a smaller, more mobile, faster-diffusing, and lower-viscosity plasticizer than DEHT. Overall, our results indicate that the most important parameters that control exudation were Hansen solubility and consequently Flory–Huggins interaction parameters.
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