Relation between the Anomalous Freezing Point Depression and the Mechanical-Elastic Behavior of Gels

Kühn, Werner; Peterli, E.; Majer, Helge

doi:10.5254/1.3542140

Cited by 23 publications

(9 citation statements)

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“…Hence, the solvent ought to have more space to crystallize [33,34]. However, according to the literature data, depression (decrease) of the freezing temperature of the solvent trapped in a polymer network may have various origins and a few theories have been proposed over the years [35,36,37,38].…”

Section: Resultsmentioning

confidence: 99%

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Sulfur/Organic Copolymers as Curing Agents for Rubber

2018

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It is widely acknowledged that waste sulfur generated from the petroleum industry creates huge storage and ecological problems. Therefore, the various methods of utilization are becoming increasingly attractive research topics worldwide. The thermal ability of elemental sulfur to homolytic cleavage of S8 rings enables its free radical copolymerization with unsaturated organic species and the obtaining of chemically stable polymeric materials. Here we report a novel possibility to use sulfur/organic copolymers obtained via “inverse vulcanization” as curatives for rubber. For this purpose, several various sulfur/organic copolymers were synthesized and analyzed from the point of view of their performance as rubber crosslinking agents. Solvent extraction was used to purify sulfur/organic copolymers from unreacted (elemental) sulfur. Thermal properties of the prepared copolymers were characterized by thermogravimetric analysis and differential scanning calorimetry (TGA–DSC). Crosslink density and structure of cured elastomers was studied by equilibrium swelling, thiol-amine analysis and freezing point depression. Mechanical properties of the vulcanizates were determined under static and dynamic conditions (DMA—dynamic mechanical analysis). It is proved that the utilization of sulfur/organic copolymers as curatives enables an effective crosslinking process of rubbers. Taking into account the results of a crosslink density analysis and mechanical properties of the vulcanizates cured with purified copolymers, it is evident that relatively long copolymer macromolecules are also involved in the formation of chemical bonds between unsaturated rubber macromolecules.

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Section: Resultsmentioning

confidence: 99%

“…W. Kuhn and co-workers [35,36] claimed that the depression of the freezing temperature of the solvent trapped in the polymer network is associated with mechanical restrictions of the network (namely the mesh width) that enforce the size of forming crystals. Free solvent surrounding the sample does not show such restrictions.…”

Section: Resultsmentioning

confidence: 99%

Sulfur/Organic Copolymers as Curing Agents for Rubber

2018

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“…It has been observed 13,14,16 that the higher the volume fraction of rubber in solvent/rubber mixtures, the lower the freezing point of the solvent. This phenomenon was described by Khun et al, 15 who proposed that the freezing point depression of solvents in solvent/ rubber mixtures or gels is related to the "mesh size" of the swollen network strands of the polymer in the gel. It was shown that the smaller the mesh size, the smaller the crystal size and the lower the observed freezing point.…”

Section: Introductionmentioning

confidence: 87%

“…Many researchers [13][14][15][16][17] have investigated the interaction between a solvent and a rubbery polymer by studying the freezing and melting behavior of the solvent. It has been observed 13,14,16 that the higher the volume fraction of rubber in solvent/rubber mixtures, the lower the freezing point of the solvent.…”

Section: Introductionmentioning

confidence: 99%

Thermal behavior of core-shell rubber/styrene monomer gels

Roberts

Simon

Cook

et al. 2000

J. Polym. Sci. B Polym. Phys.

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“…This anomalous freezing-point depression has been widely described by various authors. [13][14][15][16][17] Kuhn and Majer [13] attributed this anomaly to limited crystal growth in the gel, resulting from a mesh formed by chain segments in the polymer network. Hence, a higher vapor pressure can be expected for microcrystals because of their high surface to volume ratio, rendering a decrease in their freezing point.…”

Section: Introductionmentioning

confidence: 99%

Novel Approach of Evaluating Polymer Nanocomposite Structure by Measurements of the Freezing‐Point Depression

López–Manchado

Valentín

Herrero

et al. 2004

Macromol. Rapid Commun.

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IntroductionIn recent years, polymer/layered silicate (PLS) nanocomposites have attracted great interest, both in industry and in academia, because they exhibit unique properties not shared by their micro counterparts or conventional filled polymers. [1][2][3][4][5] The addition of just a few weight percent (<5 wt.-%) of nanolayered inorganic material gives rise to sensible increases in the stiffness and strength with minimal loss of ductility and impact resistance, [6,7] decreased gas permeability [8,9] and flammability, [10] improved abrasion and heat resistance, [11] and increased biodegradability of biodegradable polymers. [12] The physical mixture of a polymer and a layered silicate not necessarily gives rise to a nanocomposite. Depending on interfacial interactions between the polymer and layered silicates, three types of morphologies can occur: immiscible, intercalated, and exfoliated.The improved properties are only achieved when an exfoliated nanocomposite is formed. For this reason, it is very important to characterize the polymer nanocomposite structure prior to the analysis of their properties. The structure of the nanocomposites has typically been established by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Because of their easiness and availability, X-rays are most commonly used to determine the nanocomposite structure. However, one needs to be very careful with the interpretation of the results. Lack of sensibility in the analysis and limits of the equipment can lead to wrong conclusions about the nanocomposite structure. That is, the nanocomposites generally contain a fairly small amount of clay (less than 10 wt.-%), therefore the XRD analysis must be sensitive enough to detect the crystalline structure of the clay in the polymer. If this is not the case, no peaks appear in the diffraction pattern and a false conclusion, that a delaminated nanocomposite has been synthesized, might be drawn. Moreover, the analysis is Summary: A novel experimental approach based on the freezing-point depression of a solvent in a swollen gel has been developed to characterize the structure of nanocomposites. A higher depression in the freezing point has been related with an exfoliated nanocomposite. This increased depression not only depends on the formation of a tighter network but also on the decrease of the size of the solvent cages where the nucleation takes place.The nucleation process of unfilled and organoclay-filled natural rubber with the same crosslinking density.Communication 1309 performed at low angles in order to detect the (001) reflection and evaluate the spacing between the clay layers. It means that the irradiated surface may include not only the sample but also the sample holder. This might create a large amount of noise and, as a consequence, complicate the interpretation of the XRD patterns. Therefore, TEM is a necessary complement to confirm results obtained by XRD about the organization of the clay layers in the nanocomposite. TEM allows a qualitative u...

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Relation between the Anomalous Freezing Point Depression and the Mechanical-Elastic Behavior of Gels

Cited by 23 publications

References 0 publications

Sulfur/Organic Copolymers as Curing Agents for Rubber

Sulfur/Organic Copolymers as Curing Agents for Rubber

Thermal behavior of core-shell rubber/styrene monomer gels

Novel Approach of Evaluating Polymer Nanocomposite Structure by Measurements of the Freezing‐Point Depression

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