Crosslinking of elastomers resulting from ageing: use of thermoporosimetry to characterise the polymeric network with n-heptane as condensate

Baba, Mohamed; Nédélec, Jean-Marie; Lacoste, J.; Gardette, J-L.; Morel, Myriam

doi:10.1016/s0141-3910(03)00014-4

Cited by 55 publications

(42 citation statements)

References 12 publications

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“…Unlike some other systems in which the solvent displays two independent melting peaks (corresponding to the melting of bulk solvent on the surface of the gel and confined solvent inside the gel), 13,20,31 cyclohexane just has one melting peak when v 2 \ v 0 2 . As the polymer volume fraction increases from 0 to 14%, the shape and position of the melting peak of the cyclohexane remains unchanged, but the area becomes smaller as discussed subsequently.…”

Section: Melting Behavior Of Cyclohexane In Model Networkmentioning

confidence: 93%

Anomalous melting behavior of cyclohexane and cyclooctane in poly(dimethyl siloxane) precursors and model networks

McKenna

2008

J Polym Sci B Polym Phys

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Building on previous observations of anomalous melting behavior of solvents in polyisoprene, we have expanded our insight into the melting behavior of organic solvents in polymers and polymer networks through a calorimetric investigation of cylcohexane and cyclooctane in poly(dimethyl siloxane) (PDMS) precursors and model networks. The results are contrary to general expectations. Besides deviations between the predictions of the Flory-Huggins model and observed melting point depression of the small molecule organics, it is found that the melting point depression of cyclohexane in model networks is lower than that in the uncrosslinked precursors and unaffected by the molecular weight between crosslinks, which is not consistent with the general observation that higher crosslinking density leads to greater melting point depression. We interpret the observed phenomenon in terms of phase separation. In the case of cyclooctane, it exhibits a double melting peak in the model networks with high molecular weight between crosslinks. Furthermore, the heats of fusion of both cyclohexane and cyclooctane decrease with increasing polymer volume fraction which violates the underlying assumption that the heat of fusion of solvent in the polymer is the same as that in the bulk for both the Flory-Huggins model and the Gibbs-Thomson equation.

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Section: Melting Behavior Of Cyclohexane In Model Networkmentioning

confidence: 93%

Anomalous melting behavior of cyclohexane and cyclooctane in poly(dimethyl siloxane) precursors and model networks

McKenna

2008

J Polym Sci B Polym Phys

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“…The thermodynamic treatment of the phenomenon allowed the conversion of temperature shifts into porous size distribution (thermoporosimetry). We developed this approach in a few studies [7][8][9][10]. DSC was carried out using two calorimeters.…”

Section: Differential Scanning Calorimetry (Dsc)-thermoporosimetrymentioning

confidence: 99%

Durability of crosslinked polydimethylsyloxanes: the case of composite insulators

Delor‐Jestin¹,

Tomer²,

Singh³

et al. 2008

Science and Technology of Advanced Materials

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Most applications of silicones are linked to their hydrophobic properties and (or) their high resistance to ageing (e.g. thermal ageing and photoageing). However, when placed in extreme environments, these materials can fail as in the case of epoxy/fiber glass composite powerlines insulators, where crosslinked polymethylsyloxanes (PDMSs) are used as the protective envelope (housing) of the insulator. We report on the behavior of both pure/noncrosslinked PDMSs and typical formulations used in industrial insulators, i.e. containing peroxide crosslinked PDMS, alumina trioxide hydrated (ATH) and silica. Special attention is paid on both (i) the sources of potential degradation and (ii) the best analytical methods that can be applied to the study of very complex formulations. (i) Aside from conventional types of ageing such as photo-ageing and thermal, hydrolytic, and service life ageings, treatments with acidic vapors, plasma and ozone possibly generating species from the reaction of a high electric field with air were also performed, which allowed to accelerate electrical and out-door ageings and to obtain differently aged materials. (ii) Aside from conventional analytical methods of polymer degradation such as FTIR/ATR spectroscopy and SEC, TG, hardness measurements, more specific methods like photo/DSC, TG/IR, thermoporosimetry, resistivity and density measurements were also performed to characterize the chemical and physical evolutions of polymer materials. In particular, it was found that treatment with nitric acid vapor has detrimental effects on the properties of both fire retardants (e.g. ATH) and PDMSs, affecting the hardness and resistivity of the formulated material.

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“…A number of solvents including linear alkanes [22], cyclohexane [23], substituted benzene [24], CCl 4 [25,26], acetone [21], and acetonitrile [27] were tested. Various polymers like polystyrene (PS) [26], ethylene-propylene rubber (EPR) [28], ethylene-propylene-diene-monomer (EPDM) [29,30], polybutadiene, polyisoprene [31], and poly(dimethyl siloxane) (PDMS) [32], cross-linked by UV or gamma irradiation, by heating or aging degradation, were characterized and their mesh size distributions calculated.…”

Section: Thermoporosimetrymentioning

confidence: 99%

Polymer Microstructures: Modification and Characterization by Fluid Sorption

Boyer

Baba

Nédélec³

et al. 2008

Int J Thermophys

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Polymer micro-organization can be modified by a combination of three constraints, thermal, hydrostatic, and fluid sorption. In selecting the fluid's nature, chemically active or inert, and its physical state, liquid or supercritical, new "materials" can be generated. In addition, the interplay of temperature and pressure allows tailoring the obtained material structure for specific applications. Several complementary techniques have been developed to modify, analyze, and characterize the end products: scanning transitiometry, vibrating-wire (VW)-PVT coupling, thermoporosimetry, and temperature-modulated DSC (TMDSC). The great variety of possible applications in materials science is illustrated with different polymers which can produce materials from soft gel to rigid foams when submitted to fluid sorption, typical fluids being methane or a simple gas (CO 2 or N 2 ). Absorption of an appropriate fluid in a crosslinked polymer leads to a swelling phenomenon. Thermoporosimetry is a calorimetric technique developed to measure the shift by confinement of thermal-transition temperatures of the swelling fluids, which can be currently used solvents or mercury.Application of thermoporosimetry to a swollen cross-linked polymer allows calculation of the mesh size distribution and evaluation of the degree of reticulation of the polymer. The same technique can be applied to characterize the pore size distribution in a foamed polymer.

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Crosslinking of elastomers resulting from ageing: use of thermoporosimetry to characterise the polymeric network with n-heptane as condensate

Cited by 55 publications

References 12 publications

Anomalous melting behavior of cyclohexane and cyclooctane in poly(dimethyl siloxane) precursors and model networks

Anomalous melting behavior of cyclohexane and cyclooctane in poly(dimethyl siloxane) precursors and model networks

Durability of crosslinked polydimethylsyloxanes: the case of composite insulators

Polymer Microstructures: Modification and Characterization by Fluid Sorption

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