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Background Ghŗta mūrcchana is a process of pre-treatment recommended in Ayurveda to purify ghee before it can be used for siddha ghŗta which is claimed to improve the properties of the ghee in general and that of the prepared siddha ghŗta. Objective This work is aimed at studying the physiochemical properties of ghee and mūrcchita ghŗta in order to understand the impact of ghŗta mūrcchana process. Materials and methods Ghee and mūrcchita ghŗta were prepared from the milk of local Pahadi, Jersey and Holstein cows. The samples were characterized by FTIR spectroscopy, differential scanning calorimetry and free fatty acid measurements. Results Among the samples studied, the Holstein cow ghee was found to contain the least amount of free acid (1.34%) whereas ghŗta mūrcchana process led to further decrease in the free acid content polymorphism was observed in the samples as evidenced by multiple melting points. In most cases, mūrcchita ghŗta was found to contain less solid fat than the corresponding ghee implying that the high melting compound was converted to low melting one during the process. Conclusion The observed lowering of free fatty acid and solid fat contents in the ghee samples may provide a possible validation to the performance enhancement of the ghŗta mūrcchana process.

Star-shaped polystyrene-block-polybutadiene-block-polystyrene (SBS) block copolymer (BCP) was subjected to epoxidation reaction using m-chloroperoxy benzoic acid (MCPBA). The epoxidized SBS block copolymer (eSBS) was then blended with diglycidyl ether of bisphenol-A based epoxy resin (EP) and cross-linked with methylene dianiline (MDA). The materials were characterized by different techniques such as Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The FTIR spectrumwith the peak located at 890 cm−1 and 1230 cm−1 attested the occurrence of epoxidation reaction. The nanophase separated structures as demonstrated by transmission electron microscopy were induced in the eSBS/EP blends by epoxidized eSBS.

Functional grading is used to push the load capacity of parts to within the upper bound of what is theoretically possible. Using interpenetrating polymer networks (IPNs), a material system used to achieve grading during printing, the possibility of producing realistic grading of acrylate/epoxy IPNs is studied with the goal of increasing load capacity to within the limit of what is possible, and substantially beyond the load capacity possible with any uniform mixture of this IPN system. In the process, an upper bound of possible improvement is established for a plate with a circular hole in tensions, and the grading for this plate is adjusted to give an optimal load capacity near this upper bound. The optimal grading proposed is different from that shown in previous work due to the simultaneous consideration of both the effect of grading on elastic moduli and on the ultimate stress. A similar study was done for an L-shaped bracket indicating similar improvements over uniform brackets. Keywords: Functionally graded material, Interpenetrating polymer networks, Load capacity, Finite element method, Optimization

Thermostable nanocomposites based on densely cross-linked Cyanate Ester Resins (CER), derived from bisphenol E and doped by 0.01–10 wt.% epoxycyclohexyl-functionalized polyhedral oligomeric silsesquioxane (ECH-POSS), were synthesized and characterized in detail by means of TEM, SAXS, EDXS, FTIR, DSC, DMA, TGA, far-IR and creep rate spectroscopy techniques. It was revealed that ultra-low POSS contents (≪1 wt.%), covalently embedded into CER network, substantially changed its nanostructure and properties. This resulted in changing network dynamics; increasing glass transition temperatures by 20–50 °C; enhancing high temperature elastic and creep resistance properties, and increasing thermal stability under inert atmosphere at T

The temporal technique analysis by a simplex optimization method of isothermal transient depolarization current measurements (Simplex-TSDC) is presented for the study of the glass transition domain of different polymers. The advantage of the present method compared to the classical TSDC is that it gives direct results comparable to the experiment and allows a good estimate of the relaxation time close to the glass transition temperature in dielectric thin films. The present method also allows a direct determination of two relaxation times corresponding to a fast and a slow dynamics; and then confirms the heterogeneous character of the molecular relaxation dynamics.

Molecular dynamics at the glass transition of three lactose/oil glassy systems have been investigated according to the cooperativity and fragility approaches. From Donth's approach, the cooperativity length is estimated by modulated temperature calorimetric measurements. Results reveal that modification of the disaccharide by oil leads to increase the disorder degree in the lactose, the size of the cooperative domains and the fragility index. These particular hydrogen-bonded organic glasses follow the general tendency observed on organic and inorganic polymers: the higher the cooperativity length, the higher the value of the fragility index at T g .

The electrical properties of sisal fiber reinforced polyester composites fabricated by resin transfer molding (RTM) have been studied with special reference to fiber loading, frequency and temperature. The dielectric constant ( e ′), loss factor ( e ″), dissipation factor (tan δ ) and conductivity increases with fiber content for the entire range of frequencies. The values are high for the composites having fiber content of 50 vol.%. This increment is high at low frequencies, low at medium frequencies, and very small at high frequencies. The volume resistivity varies with fiber loading at lower frequency and merges together at higher frequency. When temperature increases the dielectric constant values increases followed by a decrease after the glass transition temperature. This variation depends upon the fiber content. Finally an attempt is made to correlate the experimental value of the dielectric constant with theoretical predictions.

Temperature Modulated Differential Scanning Calorimetry (TMDSC) is used to estimate Cooperative Rearranging Region (CRR) average sizes for polymer/clay nanocomposites, obtained by mixing polyethylene 1,4-cyclohexylenedimethylene terephthalate glycol (PETg) filled and organically modified nanoclay (C15A) following a master-batch process. Two different basal distances are obtained. It is shown that the greater the basal distance and the nanofiller content, the lower the heat capacity step at the glass transition temperature ΔCp(Tg), and the lower the CRR volume. It is also shown that the evolution of the CRR volume is consistent with the evolution of the fragility index obtained by DSC and Broadband Dielectric Spectroscopy (BDS) when the nanofiller content changes. The fragility index and the CRR size decreases can be correlated to nanofiller presence, hindering the molecular movements. From the Vollenberg and Heikens [34] approach, this behaviour can also be interpreted through the existence of an interfacial bilayer. This interfacial bilayer is composed by a zone, which is next to the nanofiller, with a density higher than the matrix one, followed by a more expanded zone with a density lower than the matrix one.

Arresting of segmental mobility in polymer systems on cooling from the melt was simulated by means of the Bond Fluctuation Model. In order to represent the behaviour of the system, three potentials were included: a Lennard-Jones potential, a bond length potential and a bond angle potential. The effect of the bond angle and bond length potential combination is to stretch the chains, while the Lennard-Jones potential leads to a lack of free volume which appears when temperature decreases. So, when a cooling ramp is applied, depending on the balance of these potentials, the system shows a transition in which molecules densely pack or, on the contrary, remains amorphous. Therefore, the choice in the weighting of these three potentials is a key point to simulate a physical system by using the Bond Fluctuation Model. © 2010 Elsevier Ltd. All rights reserved., The authors would like to acknowledge the support provided by the Conselleria d'Educacio of the Generalitat Valenciana through the GV/2009/033 project. This work was supported by the computer-time grant (No. 2003014) of the Centre de Ressources Informatiques de Haute Normandie (CRIHAN).

Wheat flour based thermoplastic having glycerol content (20%, 23%, 25%, 30% and 35% w/w) were fabricated using extrusion followed by compression molding. Dynamic mechanical analysis (DMA) has been done with reference to the amount of glycerol, sisal fiber loading, frequency and temperature. Two transitions peaks were observed for the, matrix, one at low temperature, due to the molecular dynamics associated to glycerol rich phase, and another at high temperature attributed to the molecular relaxation of starch rich phase. By changing the amount of glycerol, it has been observed that, at all temperature ranges, a plasticization effect which concerns mainly in the starch rich phase. Introduction of sisal fiber (up to 10% w/w) increases the storage modulus of the thermoplastic matrix. The peak height of damping curves (tan δ ) was lowered as the fiber content. The activation energy was calculated from the maximum temperature ( T max ) of damping curves.

A 100% green thermoplastic obtained by extrusion of a mixture of wheat flour and plasticizers has been realized. The existence of two vitreous phases in this 100% green thermoplastic film has been pointed out by means of calorimetric measurements ( T g =−56 °C and T g =10 °C) and confirmed by electron microscopy. The molecular dynamics have been investigated by means of DMA measurements for temperature domains in the vicinity of the glass transition of each phase. We show that each phase exhibits a molecular dynamic characteristic of a fragile glass liquid former. The size of the cooperative domain engaged in the relaxation processes have also been estimated and we show that this new green thermoplastic exhibits relaxation mechanisms as expected for a conventional thermoplastic, as for instance a PMMA.

Sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100 °C, permanganate treatment, benzoylation and silanization to improve the interfacial bonding with matrix. Composites were prepared by these fibers as reinforcement, using resin transfer molding (RTM). The mechanical properties such as tensile, flexural and impact strength were examined. Mercerized fiber-reinforced composites showed 36% of increase in tensile strength and 53% in Young’s modulus while the permanganate treated fiber-reinforced composites performed 25% increase in flexural strength. However, in the case of impact strength, the treatment has been found to cause a reduction. The water absorption study of these composites at different temperature revealed that it is less for the treated fiber-reinforced composites at all temperatures compared to the untreated one. SEM studies have been used to complement the results emanated from the evaluation of mechanical properties.

In this work, the process of co-drawing followed by bundling and restacking was used to fabricate composite wires with a metallic copper matrix and High Density Polyethylene (HDPE) polymer fibres. After processing, copper matrix composite wires with 3770 polymer domains of approximately 20 μm in diameter were obtained. Differential Scanning Calorimetry analysis, optical microscopy and microhardness measurements were performed on the polymer and the copper components of the composites. The volume fraction and the degree of crystallinity of the polymer remain constant during the drawing. This procedure leads to a lamellar reorganization and fragmentation of the crystalline HDPE phase.

New composites materials, 100% ecofriendly, having waste cotton fibre as reinforcement in wheat flour based thermoplastic matrix were prepared by extrusion method. The fibre content in the composite varied from 0 to 15% w/w. Using X-ray diffraction and scanning electron microscopy, the structure and morphology of the composites have been analysed. This investigation is focused on the effects of the fibre content on the mechanical and thermal properties of the composites. Addition of the waste cotton fibre to the matrix increased the tensile properties. For the composite with 10% w/w of fibre the values of the tensile stress are found maximum. We also show that thermal conductivity and resistivity are not affected by the fibre content. By thermogravimetry we show that the addition of fibres to the matrix has no significant influence on the thermal stability of the composites. Finally, to analyse the efficiency of the present system, a comparative study of the mechanical properties obtained with flax and cotton fibres is performed.

The effects of the incorporation of monoglyceride on the structure and thermal stability of extruded thermoplastic films based on modified wheat flour have been investigated using X-ray diffraction (XRD) and thermogravimetric method (TGA). Addition of the monoglyceride reduced the intensity and widened the peaks obtained by XRD indicating a reduction in crystal size. A significant decrease of apparent length of the crystals have been noticed when the quantity of monoglyceride increases. The thermal analysis proved that the thermal stability of the polymeric material decreases as a function of the monoglyceride content. Finally an attempt is made to correlate the thermal stability of the polymeric materials, with the degree of crystallinity.

Amorphous films of poly(ethylene terephthalate) were uniaxially drawn at temperature above the glass transition for different draw ratio λ in order to study samples with various structural states. When λ is lower than 2, the films remain practically amorphous while for higher λ values, a strain induced crystallization takes place and reaches a maximum. In regard to the Strong Fragile concept proposed by C.A. Angell, the different materials show a behaviour breaking when the draw ratio λ is greater than 3. Indeed, the weakly drawn samples show a fragile behavior, while the highly drawn samples show a strong one. Moreover, the determination of the average size of the Cooperative Rearranging Regions (CRR) proves the crystallite presence drastically reduces the CRR size in the remaining amorphous phase. This is attributed to an amorphous phase confinement effect by the crystallites and the rigid amorphous fraction.

Thermal analyzes have been performed on poly( l -lactide acid) (PLLA) annealed at 353 K for different durations in order to obtain a crystallinity degree varying between 0% and 42%. From temperature modulated differential scanning calorimetry investigations, we have calculated the average volume of a cooperative rearranging region (CRR) at the glass transition temperature ξ T g 3 , according to the method developed by Donth. The results show that the presence of crystalline phase in PLLA amorphous matrix implies modifications on structural relaxation phenomena, in particular on the average number of monomer units relaxing in the same time at the glass transition temperature.

Bulk glasses with the chemical composition Gey Se94−yIn6 (8 ⩽ y ⩽ 30 at%) have been prepared from high purity constituent elements. Fragments of the bulk glasses are used to deposit thin films by vacuum thermal evaporation. The optical band gaps (Eg s) of the as-deposited films have been measured. The allowed optical transition is found to be indirect. The relation of Eg to the covalent coordination number, Z, is demonstrated by varying the composition parameter y of the thin films. A maximum in the compositional dependence of Eg is attained at Z = 2.63. The cohesive energies (CE) of the investigated samples have also been calculated using the method suggested by the chemical bond approach. It is found that the composition dependence of the CE also possesses a peak at Z = 2.63. A plausible explanation based on the bonding considerations between the constituents has been provided for the understanding of the Eg-Z and CE-Z dependences for these Ge–Se–In thin films.

Differential scanning calorimetry measurements have been performed on elemental Se as well as on Ge x Se 94− x In 6 ( x =4, 8, and 11 at%) and on Ge y Se 88− y In 12 ( y =5, 7, and 9 at%) chalcogenide glasses. From the cooling rate dependence of the fictive temperature, the apparent activation energies, Δ h* , and the fragility indices, m , as defined in the strong–fragile glass-forming liquid concept, are determined. It is found that, in Ge–Se–In system, there is an evolution from strong ( m =67) to fragile ( m =116) glass-forming liquids. The dependence of ‘ m ’ on the mean-coordination number, Z , is also obtained. This dependence is rationalized by assuming that, in this glassy alloy system, there is a tendency for the formation of In 2 Se 3 clusters.

The values of different parameters defined in the Random Walk Model (RWM) as: the Density of Possible Metastable States g(E), the metastable state number NE, the apparent activation energy Ea/R and, the Cooperative Rearranging Regions distribution σ, have been calculated at Tg for two polymeric sample families (PVC, EVA70, PVC/EVA70 blend, and Unsaturated Polyester Resin samples). We show that these quantities allow to describe the configurational space, and we verify that the evolutions found for these different parameters versus the fragility are in a good agreement with the Strong-Fragile concept predictions.

The dipole dynamics and α-relaxation behaviour of polyvinyl chloride PVC, poly(ethylene-co-vinyl-acetate) EVA70 and blend of them EVA70/PVC have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The differential scanning calorimetry (DSC) thermograms measured on samples show a single glass transition in the analysed temperature range. These three polymers are wholly amorphous and pure PVC and pure EVA70 are miscible in the ratio 1:1. The glass transition temperature Tg decreases significantly with presence of EVA70. Furthermore, the values of apparent activation energies for molecular motions at the α-relaxation and the values of fragility index have also been determined for each sample using Moynihan expression for DSC results and Vogel–Fulcher–Tammann–Hesse (VFTH) form for DRS results. It is shown a large dependence of all the values of these parameters with the content of EVA70. Comparing these three polymers, we found that the more fragile glass forming liquid is the PVC. Fragility decreases drastically with EVA70 content. EVA70 and EVA70/PVC blend exhibit practically the same behaviour. The effect of inter- and intra-molecular interactions on fragility is discussed to explain these variations.

The effects of very long physical ageing up to 13 yr on vitreous chalcogenide glasses have been investigated for GexSe1−x glasses, x = 4 , 8 and 12 at%, by means of calorimetric methods. We show that the rejuvenation of such very old materials can be performed without any problem. More importantly, we find that a long ageing leads to a phase separation process. This could explain why the configurational (or conformal entropy) does not apparently reach its equilibrium value as already observed by Gomez Ribelles et al. (Macromolecules 28 (1995) 5867) on other polymeric materials.

In this work, dielectric and viscosimetric investigations were performed on three different kinds of polymeric structures, i.e. three samples of poly[oxy(2,2 dialkylpropane-1,3-diyl)carboxylbisphenyl-4,4′ dicarbonyl], three samples of poly-methyl (α-n-alkyl) acrylate, and four samples of unsaturated polyester resins. Using the strong-fragile concept, we characterized the glass-forming liquid by means of the fragility index m. From the random walk model (RWM), it is possible to define the quantity ΔT = (Tc − Tk), which characterizes the cooperative range, Tc being a critical temperature and Tk being the Kauzmann temperature. In this work, we show that the cooperative range and the fragility index are correlated, and more precisely that the greater the quantity (Tc − Tk), the smaller the fragility index m.

Blends of poly(acrylic acid) (PAA) and poly(sodium styrene sulfonate) (PSSNa) were prepared from polymer solutions by solvent evaporation. The observed decrease in PAA-solution pH upon addition of PSSNa suggests an inter-penetration of the two polymer chains, thus the polymer compatibility, in solution. The blend compatibility was studied with the attenuated total reflection-Fourier transform infrared (atr-FTIR) and the differential scanning calorimetry (DSC) techniques. The unique and composition-dependent glass transition temperature indicates that the two polymers are compatible, but the Δ T g broadening suggests a certain degree of nano-heterogeneity. The T g of pure PSSNa which was non-detectable in DSC, was calculated from the Fox equation. From FTIR data, the polymer compatibility could be attributed to the establishment of hydrogen bonds, and dipole–ion interactions between carboxylic groups, sulfonate groups, and sodium ion on the polymer segments.

We have studied the vitreous Ge x Se 1− x chalcogenide alloys, varying x from 0.0 to 0.12. P – V – T results have been obtained for pressures up to 200 J cm −3 and temperatures up to 240°C or so. The P *, V * and T * parameters of the Hartmann equation of state (EOS) were evaluated. With increasing Ge concentration the specific volume increases, passes through a maximum and then decreases. By contrast, the characteristic (hard-core) volume V * passes through a minimum and so does the characteristic temperature T *. On the basis of these results in conjunction with earlier ones we provide an expanded model of atomic packing and phase structures of the alloys.

According to the ‘strong-fragile’ glass forming liquid concept, amorphous poly(ethylene terephthalate) (PET) must be classified as a ‘fragile’ supercooled liquid. In this work we show that the value of the fragility index of the glassy material (mg) can be obtained by means of Thermally Stimulated Depolarisation Currents measurements. Experiments were carried out on different PET for which the molecular mobility of the vitreous domain was constrained by the existence of a crystalline phase. This crystalline phase was obtained in two different ways, i.e. by thermal cold crystallisation or by a uniaxial hot-drawing method. Depending on the degree of crystallinity, but whatever the nature of the crystalline morphology (spherulitic or oriented crystallites), it is found that the initial fragile character becomes stronger as the degree of crystallinity increases.

A poly(bisphenol A)cyanurate (PCy) network was modified by a hydroxy-terminated oligoester, poly(butylene glycol adipate), PBGA, by polycyclotrimerization of bisphenol A dicyanate in the presence of the oligoester. The modified networks with PBGA content from 5 to 20% (w/w) were characterized by a combination of FTIR, DSC, TMA, TGA, impact testing and sol-gel analysis. It has been established that almost whole of the PBGA was chemically incorporated into the PCy network structure and that the higher the content of PBGA, the stronger the interaction between the components. It is shown that introducing PBGA does not drastically reduce thermal characteristics (temperature of the thermal degradation onset and glass transition temperature) of the PCy network while the impact properties are improved significantly. It is suggested that the modified PCy can be successfully used simultaneously at high temperatures and high loading.

Two strains (an environmental strain and a reference one coming from a national culture collection) of Yersinia ruckeri , a fish pathogenic bacterium, are characterised according to the ability to adhere on wood, concrete, polyvinylchloride (PVC) and fibreglass, four materials commonly found in fish farms. The relationships between adherence, bacterial and support hydrophobicities and surface roughness are investigated. The results show that: (i) Y. ruckeri is strongly hydrophilic; (ii) the environmental strain exhibits a higher ability to adhere than the reference one; and (iii) for the two strains a strong correlation is observed between roughness amplitude (RA) of the support material and adhesion ability.

The compositional dependence of the mean atomic volume, V a , and the packing density, ρ p , of the Ge x S 94− x Bi 6 glassy system, in the range 14≤ x ≤26 ( x in at.%), have been investigated. Particular features in the compositional dependence of these physicochemical properties on the bond density, n , have been found. Specifically, at n =2.46, V a and ρ p exhibit a minimum and a maximum, respectively, whereas at n =2.56, V a displays a maximum and ρ p passes through a minimum. These features are explained using the topological arguments proposed in Phillips'–Thorpe and Tanaka's models.

After performing the synthesis of polymethyl(α- n -propyl)acrylate (C3), polymethyl(α- n -penthyl)acrylate (C5) and polymethyl(α- n -octyl)acrylate (C8) in the polymethyl(α- n -alkyl)acrylate family, we have analyzed the role of the length of the alkyl group on the molecular relaxations which occur in such amorphous material. The molecular relaxations were studied from elementary and complex spectra obtained by thermally stimulated depolarization current measurements. The analysis of the α and β modes allows the determination of the apparent activation entropy of relaxation ΔS and of the apparent activation enthalpy ΔH max at the maximum of the mode which is the dielectric manifestation of the glass transition. For the α mode, the main result shows minima in the variations of both ΔS and ΔH max with the length of the alkyl group. These minima occur for C3 samples. In the opposite, ΔS remains practically nil for the secondary β relaxation.

Dielectric measurements have been performed on unsaturated polyester resins, cured with different styrene contents. Based on the random walk model (RWM), we have determined, as a function of the styrene content, the width of the density of states kT 0 , the average energy barrier height 〈 E A 〉 that a structural unit must crossover in order to relax, the fragility index α and the value of T c at which qualitative changes in the dynamics occur. The RWM data are in good agreement with the strong-fragile concept.

The sand wind effect on the durability of low-density polyethylene (LDPE) used as greenhouse cover, kept under sub-Saharan climatic conditions, has been investigated. Sand winds were simulated with an apparatus developed in our laboratory. Infrared, UV visible spectroscopies, contact angle, interferential microscopy, differential scanning calorimetry and permeability measurements were performed on untreated samples and on samples submitted to a sand wind. The data analysis shows that the surface roughness is modified, leading to drastic decreasing of the UV–visible light transmission. This phenomenon is due to the presence of small sand particles inlaid in the sample surface and due to surface erosion. Sand wind does not affect O2 permeation but decreases the rate of water absorption. Finally, in the range of experimental duration investigated in this work, no chemical action due to sand wind is observed. # 2002 Elsevier Science Ltd. All rights reserved.

The transport of gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) of different VA contents, was studied by permeation measurements. Permeabilities, diffusivities, and solubilities were determined for EVA films containing 19, 33, 50 and 70% (w/w) VA. A low density polyethylene LDPE (used as reference with 0% VA) was also studied. The diffusion of oxygen was determined from transient permeation fluxes and the diffusion of carbon dioxide from time-lag permeation. In the case of gas permeation, whatever the VA content of the polymer used, the experimental transient fluxes are characterized by a constant diffusion coefficient for both O2 and CO2. In terms of gas permeability, compared with water permeability (Part A), these copolymers are characterized by very low coefficients, especially for oxygen. Assuming that D is constant, the O2 and CO2 solubility coefficient was then deduced and its value is shown to increase proportionally with the VA content in these rubbery copolymers (whose quantity of crystalline phases decreases and become nil for 70% VA). The H2O/CO2 and H2O/O2 ideal selectivity α increases with the VA content, in agreement with the increase in average polarity of the copolymer.

This paper discusses the preparation and characterization of nanocomposites obtained with potato starch nanocrystals, and their use as fillers in order to realize nanocomposites with a natural rubber latex matrix. The preparation of potato starch nanocrystals was done by hydrolysis of potato starch powder using sulfuric acid. The synthesized potato starch nanocrystal suspensions were mixed with natural rubber latex by latex stage mixing process using a magnetic stirrer. In this way, composites containing up to 20% w/w of fillers have been obtained. Morphological studies indicated a relatively uniform dispersion of starch nanocrystals in the nanocomposites until 15% w/w filler loading. Dielectric measurements confirm the existence of a threshold at a composition close to 15% w/w of filler at which the fillers become agglomerated.

Unsaturated polyester resins cured with varying styrene content (20–50% (w/w)) has been studied by calorimetry (DSC). We have evaluated the values of the heat capacity at the glass transition ΔCp=[Cp,l−Cp,g]T=Tg, the values of apparent activation energy Δh*, and the values of the fragility index m for each sample. It is found a constant value of ΔC p =0.29 J g −1 K−1 for all the samples while Δh* and m increase with the styrene content. These results discussed in regard with the strong fragile glass-formers concept indicate a character becoming more fragile when the amount of styrene increases. Introducing the “bead concept” proposed by Wunderlich, we show that the average elementary energy barrier that the molecular species (or relaxing units) must overstep during their relaxation process is unchanged whatever the content of styrene. The origin of the variations with the styrene content of the fragility behavior is understood by the increase of the bead number.

The values of the thermal heat-capacity changes at the glass transition temperature Tg (ΔCp=Cpl−Cpg) and the values of the apparent activation energy Δh* of the sub Tg relaxation process are determined for GexTe1−x (0.15⩽x⩽0.20) vitreous alloys by means of differential scanning calorimetry investigations. The values of Δh* are then used to determine the values of the fragility index, m. The comparison of these new data to those already obtained on the GexSe1−x vitreous system leads to conclude that both systems exhibit strong thermodynamic character. The stronger thermodynamic character is reached at the Phillips–Thorpe's floppy-to-rigid transition. On the other hand, we find that GexTe1−x exhibits a kinetically fragile character which decreases as the amount of Ge increases in the alloy.

The variations of the heat capacity ΔC p =[ C p l − C p g ] T = T g at the glass transition, and the value of the fragility index m were determined for two melamine formaldehyde resins by calorimetric investigations. These values characterise respectively the thermodynamic aspect and the kinetic aspect of the Angell “Strong–Fragile” concept. For resins cured with a neutral pH, the 3D network formed is made of massive molecular units connected together by small length chains, and the values are ΔC p =0.13 J K −1 g −1 and m =143. For acid pH curing conditions, the 3D network is made of only massive molecular units connected together and we obtain ΔC p =0.12 J K −1 g −1 and m =35. By comparing our results with the results of the literature concerning three-dimensional networks and inorganic polymers, we are able to conclude that the relaxation occurs in these systems mainly by movements involving triazine rings.

The structural relaxation of amorphous Ge 15 Te 85 is investigated by calorimetry (DSC). We have evaluated the apparent activation energy, Δ h *, the non-exponentiality parameter, β , of the stretched exponential response function and the Narayanaswamy parameter, x , which controls the relative contributions of temperature and of structure to the relaxation time. The values obtained are, x =0.67 with the peak shift method, β =0.6 with the C p ,u N and CF methods and, Δ h *=944 kJ/mol with the Moynihan's method. When these values are compared with those obtained for the Ge–Se system and applied to the structure of Ge 15 Te 85 in the glassy and liquid states, the results suggest that it is the movement of GeTe 4 tetrahedra that bring about the relaxation in Ge 15 Te 85 .

X-ray photoelectron spectroscopy measurements have been performed on n-type Bi-modified Ge 20 S 64 Bi 16 glass. The observed chemical shifts show that Bi is incorporated as a positive charged center into the matrix of Ge 20 S 80 parent glass.

The diffusion and permeation properties of liquid water through an isophthalic-maleic acid-propanediol-based copolyester resin were studied with a highly sensitive permeameter. The value of the parameters of the exponential dependence of the diffusion coefficient on the water concentration decreases with the curing extent, except that of the plasticization coefficient, which decreases after a post-curing at 120°C. Infrared-spectrophotometric and calorimetric data show that the curing involves mainly a polymerization of styrene during the curing at 25°C, and a crosslinking by the opening of the double bonds on the polyester chains in the subsequent curing step at 80°C. The water sorption by the resin results in a 20°C-decrease in the glass transition temperature of the water saturated resin, leading to the diffusivity enhancement by the plasticization effect.

Unsaturated polyester resin (UPR) films have been modified by a tetrafluoromethane microwave plasma. The treated surface morphologies investigated by contact angle, atomic force microscopy and permeation measurements show that the CF 4 plasma treatment decreases drastically the surface energy by increasing the hydrophobic character. The surface modification due to plasma fluorination decreases the water content diffusing through the UPR film and the time lag diffusion coefficient and thus, the sorption kinetic. From these results, it is clearly shown that the CF 4 plasma treated layer improves drastically the barrier effects.

Enthalpy relaxation in selenium samples and Ge x Se 1− x alloys with x =0.08 and 0.12 has been investigated by differential scanning calorimetry. All the samples have been submitted to comparable aging temperatures 10°C below the glass transition temperature for a period from 0.5 to 800 h. The apparent activation energy and the Narayanaswamy parameter, X , were calculated and the non-exponentiality parameter, β , was estimated for the samples. The introduction of the germanium atoms in the selenium chain changes the distribution of relaxation times, increases the relaxation rate per decade and decreases the apparent activation energy. No differences were observed in the Ge x Se 1− x alloys in the evaluation of these parameters.

In this work, the fragility indices, m, of some new polymers from the polymethyl(α-n-alkyl)acrylate family, with 3, 5, or 8 carbons in the side chain, were determined with the method proposed by Bohmer. We have found that the value of the fragility index decreases as the length of the lateral chain increases. We also confirm a previous work in which we found a critical length of the alkyl chain which separates two types of dependence, identified by different relaxation parameters. The correlations between the ms and the Narayanaswamy parameter are also investigated.

EXAFS measurements were performed, at the In K edge, on devitrified Ge 5 Se 80 In 15 and on a series of vitreous Ge–Se–In alloys. The results indicate that the In atoms have essentially the same local surroundings in all of the samples investigated. We found that an In atom is surrounded by three Se atoms at a distance of about 0.259 nm and forms In 2 Se 3 microclusters.

EXAFS measurements, from the In K edge, on Ge 23.33 Se 64.67 In 12 glass, have been performed. For this glass, it is found that In is only coordinated with Se atoms. By complementing the EXAFS results obtained from the fitting procedure followed in this work with the earlier reported DSC results obtained on this system, it is concluded that in this glass, the coordination number of In is equal to three. Moreover, this approach of coupling EXAFS with DSC results allows one to calibrate the Γ factor for systems which lack a reference material, or systems for which an ab initio calculation cannot be performed, as in our case.

The crystallization of As x Se 1− x from the glassy state (0.005 x x , the apparent activation energy decreases. It is also found that the dependence of the inverse of the apparent activation energy for crystallization falls linearly with the reciprocal of the mean temperature used in the experiment. The latter result unambiguously indicates that the crystallization process for As x Se 1− x , in the composition range investigated, is mainly controlled by the viscosity of the medium. Therefore, the crystallization reaction totally disappears when the amount of As atoms in the alloys reaches such a value capable of connecting enough Se chains to block their movement.

The values of the apparent activation energy (ΔE), obtained from the variations of the glass transition temperature with heating rate, were investigated for different vitreous chalcogenide alloys. We observe, for vitreous Se, that ΔE is sensitive to the connectivity of the network (number of Se-8 rings). For binary alloys SeY (Y = As, Ge), for which the Y-atoms respect the 8 — N rule, the variations of the normalized quantity ΔE syst ΔE Se with the average coordination number (m) allows the construction of a master curve ( ΔE syst ΔE Se = −2.13m + 5.26 ). From this master curve, the value of m = 2.45, proposed by Phillips, is reached for ΔEsyst = 0. We also propose the use of this master curve to determine the value of the coordination number of added atoms (Y = Te), for which the 8 — N rule seems not to be respected. We find a coordination number of Te included between 2.4 and 2.6, depending on the sample preparation.

The results obtained by many authors on the GeSeIn vitreous system, in particular, those concerning the variations of the glass transition temperature, T g , with the average coordination number, Z , are investigated from a new perspective. From the assumption that In atoms participate in the formation of In 2 Se 3 microclusters, we show that the variations of T g with Z of the alloy are consistent with Sreeram's relationship and with Tanaka's structural transition model. We conclude that In is threefold coordinated with Se atoms to form In 2 Se 3 microclusters and that these microclusters do not contribute to the variations of T g with the alloy composition.

Thermogravimetry/Fourier transform infra-red coupling analysis and thermogravimetry were performed on recycled celluloses of different compositions. Four samples were studied: one from ashless filter paper, two from recycled celluloses with 80% of chemical paper pulp and 85% of mechanical paper pulp respectively, and one from recycled cellulose the composition of which is not known. The major volatile products formed during the degradation process were identified by means of thermogravimetry/Fourier transform infra-red coupling analysis. From thermogravimetry we show that the degradation process of such recycled celluloses may be divided into two stages. The activation energies for these degradation processes were obtained using the Kissinger and Broido methods. Our data show that Broido's method allows the identification of each recycled cellulose from a knowledge of the activation energies (Ea) and the critical rate of transformation (αc).

The magnetization and thermal stability of Co 74 Fe 4 Mn 4 B 12 Si 6 amorphous ribbons are studied. The Curie temperature determined from magnetization and differential scanning calorimetry measurements is T C = 680 K. An activation energy of 3.84 eV, for the devitrification process, is determined from the Kissinger method. Our data, compared with those obtained by other authors on amorphous FeBX (X = Nd, Ho, Er), show that amorphous Co 74 Fe 4 Mn 4 B 12 Si 6 exhibits good thermal stability but not as good as metallic glasses doped with a rare earth metal.