Glass Transition Temperatures Of Mixtures Research Articles

Unlocking the Hidden Potential of Cosmetics Waste for Building Sustainable Green Pavements in the Future: A Case Study of Discarded Lipsticks.

This investigation is dedicated to unlocking the hidden potential of discarded cosmetics towards building green sustainable road pavements in the future. It is particularly aiming at exploring waste lipstick (WLS) as a high-quality functional additive for advanced asphalt mix technologies. To fuel this novel innovation, the effect of various WLS doses (e.g., 5, 10, and 15 wt.%) on the performance of base AP-5 asphalt cement was studied in detail. A wide array of cutting-edge analytical lab techniques was employed to inspect in-depth the physicochemical, microstructural, thermo-morphological, and rheological properties of resultant admixtures including: elemental analysis, Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thin-layer chromatography-flame ionization detection (TLC-FID), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), needle penetration, ring and ball softening point, Brookfield viscometer, ductility, and dynamic shear rheometer (DSR) tests. Unlike the unstable response of asphaltenes, the additive/artificial aging treatments increased the fraction of resins the most, and decreased that of aromatics; however, asphaltenes did not impair the saturates portion, according to Iatroscan research. FT-IR scan divulged that the WLS-asphalt interaction was physical rather than chemical. XRD diagnosis not only revealed an obvious correlation between the asphaltenes content and the fresh-binder crystallinity but also revealed the presence of fillers in the WLS, which may generate outstanding technical qualities to bituminous mixes. According to AFM/SEM analyses, the stepwise incorporation of WLS grew the magnitude of the “bee-shaped” microstructures and extended the roughness rate of unaged/aged binders. The prolonged consumption of the high thermal-stable additive caused a remarkable drop in the onset degradation and glass transition temperature of mixtures, thus enhancing their workability and low-temperature performance, according to TGA/DTGA/DSC data. The DSR and empirical rheological experiments demonstrated that the WLS could effectively lower the manufacturing and compaction temperatures of asphalt mixes and impart them with valuable anti-aging/fatigue-cracking assets. In a nutshell, the use of waste lipstick as an asphalt modifier is viable and cost-effective and could attenuate the pollution arisen from the beauty sector, while improving the performance of hot/warm asphalt mixes (HAM/WAM) and extending the service life of roadways.

Theory for Glassy Behavior of Supercooled Liquid Mixtures.

We present a model for glassy dynamics in supercooled liquid mixtures. Given the relaxation behavior of individual supercooled liquids, the model predicts the relaxation times of their mixtures as temperature is decreased. The model is based on dynamical facilitation theory for glassy dynamics, which provides a physical basis for relaxation and vitrification of a supercooled liquid. This is in contrast to empirical linear interpolations such as the Gordon-Taylor equation typically used to predict glass transition temperatures of liquid mixtures. To understand the behavior of supercooled liquid mixtures we consider a multicomponent variant of the kinetically constrained East model in which components have a different energy scale and can also diffuse when locally mobile regions, i.e., excitations, are present. Using a variational approach we determine an effective single component model with a single effective energy scale that best approximates a mixture. When scaled by this single effective energy, we show that experimental relaxation times of many liquid mixtures all collapse onto the "parabolic law" predicted by dynamical facilitation theory. The model can be used to predict transport properties and glass transition temperatures of mixtures of glassy materials, with implications in atmospheric chemistry, biology, and pharmaceuticals.

Physical state of 2-methylbutane-1,2,3,4-tetraol in pure and internally mixed aerosols

Abstract. 2-Methylbutane-1,2,3,4-tetraol (hereafter named tetraol) is an important oxidation product of isoprene and can be considered as a marker compound for isoprene-derived secondary organic aerosols (SOAs). Little is known about this compound's physical phase state, although some field observations indicate that isoprene-derived secondary organic aerosols in the tropics tend to be in a liquid rather than a solid state. To gain more knowledge about the possible phase states of tetraol and of tetraol-containing SOA particles, we synthesized tetraol as racemates as well as enantiomerically enriched materials. Subsequently the obtained highly viscous dry liquids were investigated calorimetrically by differential scanning calorimetry revealing subambient glass transition temperatures Tg. We also show that only the diastereomeric isomers differ in their Tg values, albeit only by a few kelvin. We derive the phase diagram of water–tetraol mixtures over the whole tropospheric temperature and humidity range from determining glass transition temperatures and ice melting temperatures of aqueous tetraol mixtures. We also investigated how water diffuses into a sample of dry tetraol. We show that upon water uptake two homogeneous liquid domains form that are separated by a sharp, locally constrained concentration gradient. Finally, we measured the glass transition temperatures of mixtures of tetraol and an important oxidation product of α-pinene-derived SOA: 3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA). Overall, our results imply a liquid-like state of isoprene-derived SOA particles in the lower troposphere at moderate to high relative humidity (RH), but presumably a semisolid or even glassy state at upper tropospheric conditions, particularly at low relative humidity, thus providing experimental support for recent modeling calculations.

Effect of water content on the glass transition temperature of mixtures of sugars, polymers, and penetrating cryoprotectants in physiological buffer.

Long-term storage of viable mammalian cells is important for applications ranging from in vitro fertilization to cell therapy. Cryopreservation is currently the most common approach, but storage in liquid nitrogen is relatively costly and the requirement for low temperatures during shipping is inconvenient. Desiccation is an alternative strategy with the potential to enable viable cell preservation at more convenient storage temperatures without the need for liquid nitrogen. To achieve stability during storage in the dried state it is necessary to remove enough water that the remaining matrix forms a non-crystalline glassy solid. Thus, the glass transition temperature is a key parameter for design of cell desiccation procedures. In this study, we have investigated the effects of moisture content on the glass transition temperature (Tg) of mixtures of sugars (trehalose or raffinose), polymers (polyvinylpyrrolidone or Ficoll), penetrating cryoprotectants (ethylene glycol, propylene glycol, or dimethyl sulfoxide), and phosphate buffered saline (PBS) solutes. Aqueous solutions were dried to different moisture contents by equilibration with saturated salt solutions, or by baking at 95°C. The glass transition temperatures of the dehydrated samples were then measured by differential scanning calorimetry. As expected, Tg increased with decreasing moisture content. For example, in a desiccation medium containing 0.1 M trehalose in PBS, Tg ranged from about 360 K for a completely dry sample to about 220 K at a water mass fraction of 0.4. Addition of polymers to the solutions increased Tg, while addition of penetrating cryoprotectants decreased Tg. Our results provide insight into the relationship between relative humidity, moisture content and glass transition temperature for cell desiccation solutions containing sugars, polymers and penetrating cryoprotectants.

The amorphous state: first-principles derivation of the Gordon-Taylor equation for direct prediction of the glass transition temperature of mixtures; estimation of the crossover temperature of fragile glass formers; physical basis of the "Rule of 2/3".

Predicting the glass transition temperature (Tg) of mixtures has applications that span across industries and scientific disciplines. By plotting experimentally determined Tg values as a function of the glass composition, one can usually apply the Gordon-Taylor (G-T) equation to determine the slope, k, which subsequently can be used in Tg predictions. Traditionally viewed as a phenomenological/empirical model, this work proposes a physical basis for the G-T equation. The proposed equations allow for the calculation of k directly and, hence, they determine/predict the Tg values of mixtures algebraically. Two derivations for k are provided, one for strong glass-formers and the other for fragile mixtures, with the modeled trehalose-water and naproxen-indomethacin systems serving as examples of each. Separately, a new equation is described for the first time that allows for the direct determination of the crossover temperature, Tx, for fragile glass-formers. Lastly, the so-called "Rule of 2/3", which is commonly used to estimate the Tg of a pure amorphous phase based solely on the fusion/melting temperature, Tf, of the corresponding crystalline phase, is shown to be underpinned by the heat capacity ratio of the two phases referenced to a common temperature, as evidenced by the calculations put forth for indomethacin and felodipine.

Glass transition temperatures of mixtures of sugars, polymers, and penetrating cryoprotectants

Glass transition temperatures of mixtures of sugars, polymers, and penetrating cryoprotectants

Solubility parameters of hypromellose acetate succinate and plasticization in dry coating procedures

Solubility parameters of HPMCAS have not yet been investigated intensively. On this account, total and three-dimensional solubility parameters of HPMCAS were determined by using different experimental as well as computational methods. In addition, solubility properties of HPMCAS in a huge number of solvents were tested and a Teas plot for HPMCAS was created. The total solubility parameter of about 24 MPa0.5 was confirmed by various procedures and compared with values of plasticizers. Twenty common pharmaceutical plasticizers were evaluated in terms of their suitability for supporting film formation of HPMCAS under dry coating conditions. Therefore, glass transition temperatures of mixtures of polymer and plasticizers were inspected and film formation of potential ones was further investigated in dry coating of pellets. Contact angles of plasticizers on HPMCAS were determined in order to give a hint of achievable coating efficiencies in dry coating, but none was found to spread on HPMCAS. A few common substances, e.g. dimethyl phthalate, glycerol monocaprylate, and polyethylene glycol 400, enabled plasticization of HPMCAS; however, only triethyl citrate and triacetin were found to be suitable for use in dry coating. Addition of acetylated monoglycerides to triacetin increased coating efficiency, which was likewise previously demonstrated for triethyl citrate.

Caking Development in Lemon Juice Powder

Spray dried fruit juice powders are produced around the world. These powders contain fruit sugars and acids that make them impossible to dry without the addition of a drying aid such as maltodextrin which is added to raise the glass transition of the mixture. Thus, prediction of the glass transition temperature of mixtures is important when working out how much maltodextrin to add and at what conditions to run the spray drier. Even with maltodextrin added, the powders have a strong tendency to cake. This paper compares the glass transition temperature as measured over a range of water activities with a DSC with predictions based on a simple additive model that uses the Gordon Taylor approach for predicting the effect of water of individual component glass transition temperatures and the Fox equation. It demonstrates the development of caking between spray dried lemon juice particles with time when the temperature of the powder is raised above the glass transition temperature using two techniques.The predicted glass transition temperatures for powder made from juice, using the initial analysis were typically 29°C too high compared to the measured values over a range of water activities. This was reduced to 22°C when the compositional analysis for the juice was obtained and used. An artificial powder was made using the same ratio of maltodextrin to food sugars and acids and the Tg was measured at 23.4°C at a water activity of 0.28 which corresponds to a predicted Tg of 33.2°C.The powder was put into 28mm diameter by 4mm deep dishes and then placed in a constant RH and temperature cabinet (RH = 26% to match the water activity of the powder, with the temperature set at 7, 12 and 22°C above the measured Tg of 18°C). The level of caking was measured by the blow tester and by penetration force measurement. Both methods showed the linear development of caking strength with time and that the rate of caking was a strong function of T-Tg.Only a single measurement per sample was possible with the blow tester as it tended to destroy the small sample cakes. Multiple readings were not possible due to the limited supply of powder. With the penetration method 6 to 8 readings were taken per sample. It was found that small lumps affected the penetration measurement and less scatter occurred when these were sieved out. The penetration method was also able to follow the caking to higher caking strengths, although there was more scatter in the data for the more strongly caked samples.

Entropy of Mixing and the Glass Transition of Amorphous Mixtures

Different equations have been proposed for estimating the glass transition temperature of amorphous mixtures. All such expressions lack a term to account for the effect of the entropy of mixing on the glass transition. An entropy based analysis for the glass transition of amorphous mixtures is presented. The treatment yields an explicit mixing term in the expression for the glass transition temperature of a mixture. The obtained expression reduces to the Couchman-Karasz equation in the limiting case where the contribution of the entropy of mixing approaches zero. Equivalent expressions are obtained for the glass transition temperature of a mixture of two glass formers as for the effect of a plasticizing liquid diluent on the glass transition temperature of an amorphous material.

Diallyl orthophthalate as a reactive plasticizer for improving PVC processibility. Part I: Polymerization kinetics

The thermal radical curing of four diallylic monomers were studied and was found to be very similar. Dynamic DSC of diallyl orthophthalate (DAOP) showed a strong correlation between the cure rate and the half life temperature of the initiator employed. The extent of allylic cure was found by DSC to be very dependent on the reactivity of the initiator due to a dead-end effect, and to rise towards a plateau value with increasing initiator levels. DAOP was blended with poly(vinyl chloride) (PVC) in various weight ratios by both solution and melt compounding. The compatibility between DAOP and PVC was analysed by measuring the glass transition temperatures of mixtures with dynamic mechanical thermal analysis which showed that DAOP monomer and PVC were fully miscible regardless of the composition. The cure rate of the DAOP/PVC blends was found by dynamic DSC and isothermal NIR to increase with higher levels of PVC due to a gel effect accentuated by grafting to the PVC, while the final extent of cure decreased because of topological constraints.

The glass transition temperatures of sugar mixtures

We measured the glass transition temperatures of mono-, di-, and trisaccharide mixtures using differential scanning calorimeter (DSC) and analyzed these temperatures using the Gordon–Taylor equation. We found that the glass transition temperatures of monosaccharide–monosaccharide and disaccharide–disaccharide mixtures could be described by the conventional Gordon–Taylor equation. However, the glass transition temperatures of monosaccharide–disaccharide and monosaccharide–trisaccharide mixtures deviated from the conventional Gordon–Taylor equation and the amount of deviation in the monosaccharide–trisaccharide mixtures was larger than those in the monosaccharide–disaccharide mixtures. From these results, we conclude that the size and shape of the sugars play an important role in the glass transition temperature of the mixtures.

GLASS TRANSITION TEMPERATURE BEHAVIOR OF A MODEL BLEND OF CARBOHYDRATESCOMPORTAMIENTO DE LA TEMPERATURA DE TRANSICIÓN VÍTREA DE UNA MEZCLA MODELO DE CARBOHIDRATOSCOMPORTAMENTO DA TEMPERATURA DE TRANSICIÓN VÍTREA DUNHA MEZCLA MODELO DE CARBOHIDRATOS

The glass transition of amorphous food materials in processing and storage of foods is important. The effect of a quaternary model mixture from glucose, fructose, sucrose and water on the glass transition temperature was determined. State and phase diagrams were elaborated as well solubility curves of these mixtures. The measurements of glass transition temperature of mixtures and pure components were carried out on a differential scanning calorimeter. An empirical model was created to involve the mixture behavior. The carbohydrates present in the mixture had influence between them in the glass transition temperature determination. The solubility of glucose and sucrose showed a linear behavior with a change of first order. The solubility of fructose pointed out the presence of eutectics to high and low concentration of fructose, having a high change in the molecular arrangement between 140 and 150°C, as a result the fructose had molecular rejection to glucose and sucrose. © 2005 Altaga. All rights reserved. Resumen La transición vítrea de materiales alimentarios heterogéneos en el procesado y almacenaje de alimentos es importante. En este estudio se determinó el efecto de una mezcla modelo cuaternaria de glucosa, fructosa, sacarosa y agua sobre la temperatura de transición vítrea. Se elaboraron diagramas de fase y estado, así como curvas de solubilidad de las mezclas. Las medidas de temperatura de transición vítrea de las mezclas y componentes puros se realizaron con un calorímetro diferencial de barrido. Se desarrolló un modelo empírico para definir el comportamiento de las mezclas. Los carbohidratos presentes en las mezclas tuvieron influencia sobre la temperatura de transición vítrea. La solubilidad de glucosa y sacarosa mostró un comportamiento lineal con cambios de primer orden. La solubilidad de fructosa apuntó la presencia de eutécnicos de concentración alta y baja de fructosa, teniendo un gran cambio en su conformación molecular entre 140°C y 150°C, con el resultado de que la fructosa mostró un rechazo hacia la glucosa y sacarosa. © 2005 Altaga. Todos los derechos reservados. Palabras clave: Palabras chave, Carbohidratos, transición vítrea, solubilidade. Resumo A transición vítrea de materiais alimentarios heteroxéneos no procesado e almacenaxe de alimentos é importante. Neste estudio determinóu-se o efecto dunha mezcla modelo cuaternaria de glucosa, fructosa, sacarosa e auga sobre a temperatura de transición vítrea. Elaboráron-se diagramas de fase e estado, así como curvas de solubilidade das mezclas. As medidas de temperatura de transición vítrea das mezclas e compoñentes puros realizáron-se cun calorímetro diferencial de barrido. Desenrolou-se un modelo empírico para defini-lo comportamento das mezclas. Os carbohidratos presentes nas mezclas tiveron influencia sobre a temperatura de transición vítrea. A solubilidade de glucosa e sacarosa amosou un comportamento lineal con cambios de primeiro orde. A solubilidade de fructosa apuntou a presencia de eutécnicos de concentración alta e baixa de fructosa, tendo un gran cambio na súa conformación molecular entre 140°C e 150°C, co resultado de que a fructosa amosou un rechazo cara a glucosa e sacarosa. © 2005 Altaga. Tódolos dereitos reservados. Palabras clave: Carbohidratos, transición vítrea, solubilidad.

Structural Characteristics and Thermal Transformations of a Poly(dimethylphenylsiloxane)-Polyurethane (Glycol Diisocyanate Oligomer) Mixture Prepared by Reactive Processing in a Toluene Solution

Semi-interpenetrating networks are prepared by reactive processing of cross-linked poly(dimethylphenylsiloxane) (PDMPS) and linear polyurethane (PU). Their structure and thermal properties are investigated by wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and IR spectroscopy. The characteristic size of nanophase-separated regions is approximately equal to 102 nm. The fine structure of the polymer components in domains formed is retained on a nanometer scale. The WAXS curves of the mixtures are characterized by additive contributions for all the concentrations under investigation. This indicates that the microphase separation occurs on the molecular level. The glass transition temperatures of mixtures are virtually equal to that of linear polyurethane (− 65°C). The polymer mixtures are destructed in the temperature range 240–700° C. In this range, the DSC curves exhibit thermal effects characteristic of individual polymers.

Intermolecular interactions and phase equilibria in nitrocellulose -s-diethyldiphenylurea system

Abstract Values of the Flory-Huggins interaction parameters c were predicted on the base of mixing enthalpy H M for nitrocellulose-s-diethyldiphenylurea system. The phase diagram of the system and the glass transition temperature of mixtures T g12 were estimated using calculated c parameters. The predicted glass transition temperatures were in accordance with values determined experimentally.

The glass transition temperature of mixtures of trehalose and hydroxyethyl starch

Although mixtures of HES and sugars are used to preserve cells during freezing or drying, little is known about the glass transition of HES, or how mixtures of HES and sugars vitrify. These difficulties may be due to the polydispersity between HES samples or differences in preparation techniques, as well as problems in measuring the glass transition temperature ( T g) using differential scanning calorimetry (DSC). In this report, we examine the T g of mixtures of HES and trehalose sugar with <1% moisture content using DSC measurements. By extrapolating these measurements to pure HES using the Gordon–Taylor and Fox equations, we were able to estimate the T g of our HES sample at 44 °C. These results were additionally confirmed by using mixtures of glucose–HES which yielded a similar extrapolated T g value. Our approach to estimating the glass transition temperature of HES may be useful in other cases where glass transitions are not easily identified.

The Physical State of Mannitol after Freeze-Drying: Effects of Mannitol Concentration, Freezing Rate, and a Noncrystallizing Cosolute

The objectives of this study were to (1) measure the effects of freezing rate and mannitol concentration on the physical state of freeze-dried mannitol when mannitol is present as a single component, (2) determine the relative concentration threshold above which crystalline mannitol can be observed by X-ray powder diffraction in the freeze-dried solid when a variety of noncrystallizing solutes are included in the formulation, and (3) measure the glass transition temperature of amorphous mannitol and to determine the degree to which the glass transition temperature of freeze-dried solids consisting of mannitol and a disaccharide is predicted by the Gordon–Taylor equation. Both freezing rate and mannitol concentration influence the crystal form of mannitol in the freeze-dried solid when mannitol is present as a single component. Slow freezing of 10% (w/v) mannitol produces a mixture of the α and β polymorphs, whereas fast freezing of the same solution produces the δ form. Fast freezing of 5% (w/v) mannitol results primarily in the β form. The threshold concentration above which crystalline mannitol is detected in the freeze-dried solid by X-ray diffraction is consistently about 30% (w/w) when a second, noncrystallizing solute is present, regardless of the nature of the second component. The glass transition temperature of amorphous mannitol measured from the quench-cooled melt is approximately 13°C. Accordingly, mannitol is an effective plasticizer of freeze-dried solids when the mannitol remains amorphous. Glass transition temperatures of mixtures of mannitol and the disaccharides sucrose, maltose, trehalose, and lactose are well predicted by the Gordon–Taylor equation with values of k in the range of 3 to 4.

Viscoelastic and Mechanical Properties of Epoxy/Mixed Amine Systems. Influence of Stoichiometry and Cure Conditions

Epoxy networks based on the diglycidyl ether of bisphenol A (DGEBA) and a mixture of an aliphatic triamine and a difunctional cycloaliphatic diamine were studied. The glass transition temperatures of mixtures with different stoichiometric ratios were analysed by differential scanning calorimetry and dynamic mechanical techniques. The influence of the cure schedule was also studied for all mixtures, post-cured and not fully cured. Differences in crosslink densities were studied in the glass transition region. By using the average molecular weight between crosslinks, calculated using the rubber elasticity theory, the correlation between the glass transition temperature of cured systems and that corresponding to the unreacted system was determined. The variation of the glass transition temperatures was interpreted in terms of the macromolecular chain motions. Flexural properties such as modulus, strength, and strain to break were measured for the post-cured mixtures with different stoichiometrics.

Viscoelastic and Mechanical Properties of Epoxy/Mixed Amine Systems. Influence of Stoichiometry and Cure Conditions

Epoxy networks based on the diglycidyl ether of bisphenol A (DGEBA) and a mixture of an aliphatic triamine and a difunctional cycloaliphatic diamine were studied. The glass transition temperatures of mixtures with different stoichiometric ratios were analysed by differential scanning calorimetry and dynamic mechanical techniques. The influence of the cure schedule was also studied for all mixtures, post-cured and not fully cured. Differences in crosslink densities were studied in the glass transition region. By using the average molecular weight between crosslinks, calculated using the rubber elasticity theory, the correlation between the glass transition temperature of cured systems and that corresponding to the unreacted system was determined. The variation of the glass transition temperatures was interpreted in terms of the macromolecular chain motions. Flexural properties such as modulus, strength, and strain to break were measured for the post-cured mixtures with different stoichiometrics.