Effect Of Glass Transition Temperature Research Articles

Effect of Glass Transition Temperature on Enhanced Dielectric Breakdown Strength and Lifetime of Multilayer Polymer Films.

High temperature, high energy density, and low loss dielectric films are promising candidates for miniaturized capacitors in electric vehicles and high-speed trains. However, single-component polymers could not achieve these desired properties simultaneously. Polymer multilayer films (MLFs), which combine a high dielectric constant polymer [e.g., poly(vinylidene fluoride) (PVDF)] and a high breakdown/low loss polymer [e.g., polycarbonate (PC)] in a unique layered structure, have the potential achieve them at the same time. In this work, the effects of PC glass transition temperature (Tg) on the dielectric insulation properties (breakdown strength and lifetime) were investigated at high temperatures of 100-150 °C. Three PC materials had Tg values of 145 (PC1), 165 (PC2), and 185 °C (PC3), respectively. It is observed that MLF-PC3 with the highest Tg of PC exhibited the highest Weibull direct/alternating current (DC/AC) breakdown strength and the longest DC/AC lifetime, whereas MLF-PC1 with the lowest Tg showed the lowest Weibull DC/AC breakdown strength and the shortest DC/AC lifetime. A high-temperature high-volage leakage current study revealed that MLF-PC3 exhibited the lowest bulk conductivity at all temperatures under different electric fields. The knowledge obtained from this study will help us design better MLFs with high performance for next-generation miniaturized capacitors.

Atomization of Cocoa Honey Using Whey Protein Isolate to Produce a Dry Formulation with Improved Shelf Life for Industrial Application.

Cocoa honey, a by-product obtained during the processing of cocoa, is a juice rich in pectin, organic acids, minerals and phenolic compounds with antioxidant properties. Fresh cocoa honey is quickly fermented due to its high content of reducing sugars, such as fructose and glucose, which limits its shelf life. Currently, cocoa honey is only commercialized in frozen form, as logistical challenges prevent the wide distribution or export of this by-product for applications in the market of sweets, jellies, beverages, confectionery, and nutraceutical foods among others. Spray-drying technology is a viable prospect for the large-scale stabilization of products such as cocoa honey, with less heat exposure compared to other conventional drying methods. This work aimed to evaluate the efficacy of drying adjuvants for a rapid removal of the water present in cocoa honey via atomization, since this process minimizes the effects of glass transition temperature (Tg) related to materials with high sugar contents. Physical parameters such as the moisture content, hygroscopicity, particle size, and yield of the products obtained were determined. Cocoa honey presented 85.3 ± 0.20 g/100 g of moisture. The formulations successfully decreased moisture content, which was lower than 11.72 ± 0.08 g/100 g in the formulations. Water activity ranged between 0.1464 ± 0.0043 and 0.1562 ± 0.029, with no significant difference between the formulations. The hygroscopicity of cocoa honey powders ranged from 29.29 to 29.87 g of water/100 g of cocoa honey. The combination of 20% maltodextrin and 1% whey protein isolate (WPI) led to the best yield, resulting in a free-flowing powder as the final product. On the other hand, the formulation composed of maltodextrin and whey protein isolate in the ratio of 29:1, respectively, led to the most stable product, with less loss of phenolic compounds during the drying process (6.04%). Regarding particle diameter, 90% of the accumulated distribution did not exceed 57 μm. The greatest dispersion of particles occurs in the Ma20W10 formulation with a span of 2.72, inferring greater variation in size between small (7.01 ± 0.06 μm), medium (18.25 ± 0.37 μm), and large (56.65 ± 1.17 μm) particles. The use of whey protein isolate as an adjuvant proved to be an efficient drying process in the production of cocoa honey powder, and was also advantageous for enriching the nutritional content of the final product due to its protein origin. Furthermore, the combination of spray-drying technology and the use of whey protein isolate as adjuvant led to a free-flowing cocoa honey powder with an adequate particle size and benefits in terms of shelf-life extension, providing new opportunities for the commercialization of cocoa honey as an ingredient for the food industry, with benefits for the circular economy.

Mechanical vs calorimetric glass transition temperature in the oxidation of linoleic acid from condensed κ-carrageenan/glucose syrup systems

Lipid oxidation remains a concern leading to deterioration of the organoleptic quality in processed goods, but it should be minimized by considering changes in the structural properties of foods. The present work investigates the effect of glass transition temperature on the oxidation of linoleic acid at different concentrations of κ-carrageenan/glucose syrup. A combination of 0.5, 1, 2 and 3% (w/w) κ-carrageenan and 82.5, 82, 81, 80% (w/w) glucose syrup were mixed with 1.5% (w/w) linoleic acid and 0.5% (w/w) lecithin to prepare samples with a total solid content of 85% (w/w). Physicochemical properties of these mixtures were recorded using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). This was followed by estimation of the mechanical (Tgm) and calorimetric (Tgc) glass transition temperatures using small deformation dynamic oscillation in-shear and modulated differential scanning calorimetry (MDSC). The linoleic acid oxidation in the condensed polysaccharide/co-solute system was evaluated by monitoring the accumulation of hydroperoxide (ROOH) with UV–vis spectroscopy over a wide temperature range (−25 to 0 °C). The oxidation phase was modelled following a sigmoidal kinetic model indicating initiation and propagation stages of lipid oxidation. ROOH production increased as a function of time and temperature. The structural relaxation of the polymeric matrix influenced the oxidation rate at the initiation stage. At the propagation phase, Tgm appears to control the rate of ROOH formation (kf) and decomposition (kd) in all preparations, as compared to Tgc, an outcome that makes the former an important concept of quality control.

The effect of glass transition temperature of commercial epoxy–amine coatings on their performance in marine environment

The effect of glass transition temperature of commercial epoxy–amine coatings on their performance in marine environment

Effect of Glass Transition Temperature on the Viscosity of Carbohydrate Solutions and Fruit Juices as Functions of Temperature and Solute Concentration

Effect of Glass Transition Temperature on the Viscosity of Carbohydrate Solutions and Fruit Juices as Functions of Temperature and Solute Concentration

Flexural analysis of thermally actuated fiber reinforced shape memory polymer composite

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C0 continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (Tg). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

Effect of Microfibrillated Cellulose Loading on Physical Properties of Starch/Polyvinyl Alcohol Composite Films

The starch/polyvinyl alcohol (PVA)/microfibrillated cellulose (MFC) composite films were prepared using solution casting method after adding MFC into starch/PVA blend matrix. The effects of MFC content on the mechanical properties of starch/PVA composite films were investigated. As MFC content increases, the elongation at break and tensile strength increase firstly and then decrease. When the content of MFC is 2wt%, the tensile strength is 26.6 MPa and reaches the maximum. Through Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), good dispersion of MFC in starch/PVA matrix at the loading of 2wt%, lower crystallinity of the starch/PVA/MFC films in comparison with starch/PVA blend and the effect of glass transition temperature increasing with MFC content from 0.5wt% to 4wt% can be found observed. And, incorporating MFC does not change the composition and crystal structure of the starch/PVA composite films. Thus, the reinforcing mechanism for the improvement of mechanical properties is attributed to the homogeneous dispersion of MFC with large aspect ratio, good compatibility and interfacial interactions between starch/PVA blend matrix and MFC.

Binder-free dry particulate coating process using a mild vibration field: Effects of glass-transition temperature and powdering method of polymeric coating agents on coating performance

We employed a new dry coating process with mild-intensity vibration to prepare a 100-µm-sized microparticle capable of prolonged release of a drug. To accomplish this without using a binder, a series of laboratory-made acrylic latexes with different glass transition temperatures (Tg) ranging from 30 °C to 80 °C were employed as coating agents, and the effects of Tg and powdering method of the coating agents on coating performance were investigated. The laboratory-made acrylic latexes were powdered by spray-drying (SD) or freeze-drying (FD). Diclofenac sodium (DS)-loaded ion-exchange-resin with particle size ∼100 µm was used as a core particle. The process utilized vibrations with amplitude of 0.5 mm and frequency of 90 Hz to form an ordered mixture composed of the core particles with the loosely-layered coating agents. Subsequently, the coating agents were fixed mechanically on the core particle by impaction of zirconia beads. The coating agents powdered by FD showed higher coating efficiencies than those powdered by SD, irrespective of the differences in Tg values. Among the coating agents powdered by FD, the particles coated at Tg = 60 °C exhibited the most prolonged drug-release, although the coating efficiency was not the highest. In our proposed process utilizing mild vibration, we demonstrated that adjusting the Tg of the coating agents is crucial to the formation of binder-free multiple coating layers for prolonged drug release.

Improvement in Low Temperature Izod Impact Strength of SAN/ASA/HNBR Ternary Blends Considering Competing Effects of Glass Transition Temperature and Compatibility

The competing effects of glass transition temperature (Tg) and compatibility on the low temperature Izod impact toughness of styrene–acrylonitrile copolymer/acrylonitrile–styrene‐acrylate terpolymer (SAN/ASA, 75/25, w/w) blends were investigated by using a series of hydrogenated nitrile butadiene rubbers (HNBRs) with different acrylonitrile (AN) contents. The results showed that the HNBR with AN mass content ranging from 21% to 43% had good compatibility with polymer matrix and exhibited dramatic toughening effect at 25°C. Owing to their low Tgs, only the HNBRs (AN = 21% and 25%) remained favorable toughening effect at 0 and −30°C, respectively. Furthermore, the HNBR with 0% AN content was represented by butadiene rubber (BR). Although, BR has an extremely low Tg (−94.5°C), it is incompatible with polymer matrix, and then could not toughen the material at three temperatures (−30, 0, and 25°C, respectively). Various characterizations including solubility parameters, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR) spectroscopy, and so on were carried out to elucidate the toughening mechanism. J. VINYL ADDIT. TECHNOL., 25:225–235, 2019. © 2018 Society of Plastics Engineers

Effect of glass transition temperature on heat‐responsive gas bubbles formation from polymers containing tert‐butoxycarbonyl moiety

ABSTRACTVarious types of polymers containing tert‐butoxycarbonyl (BOC) moiety as the typical protecting group of functional moieties have been used for the design of stimuli‐responsive polymer materials. In this study, we investigated the heat‐responsive deprotection behavior of BOC‐containing polymers obtained by radical polymerization of 4‐(tert‐butoxycarbonyloxy)styrene (BSt) and copolymerizations of BSt with styrene and methyl acrylate. The deprotection of BOC groups accompanying the evolution of isobutene and carbon dioxide as gaseous products was monitored by thermogravimetric analyses at different temperature circumstances; that is, on heating at a rate of 10 °C/min and under isothermal conditions at various temperatures. The deprotection resulted in a significant decrease in the transmittance of visible light due to the formation of a large number of gas bubbles, that is, foaming, in the polymer films when a heating temperature was close to the glass transition temperature of the used polymer. The potential of BOC‐containing polymers was also evaluated as the heat‐responsive adhesive polymers for dismantlable adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46252.

Drug release behavior of hydrophobic drug-loaded poly (lactide-co-glycolide) nanoparticles: Effects of glass transition temperature

Poly(lactide-co-glycolide) has been widely used and studied because of its biocompatibility and biodegradability. Recently, effects of physicochemical properties of poly(lactide-co-glycolide) on drug release behavior of hydrophobic drug-loaded nanoparticles were studied, and it was suggested that the glass transition temperature (Tg) of copolymers greatly affected the drug release. In this study, we prepared rifampicin-loaded nanoparticles with 180-nm diameter using poly(DL-lactide-co-glycolide) (PLGA), poly(L-lactide-co-glycolide) (PLLGA), and their physical mixtures. We determined the crystalline states, glass transition temperatures, and in vitro release studies were carried out in phosphate-buffered saline at 37°C for 48h. The results of the drug release studies of PLGA nanoparticles with three different molecular weights indicated that the molecular weight had a greater influence on the drug release behavior than Tg in the molecular weight range of 10,000–20,000. Also, from the results of release studies of nanoparticles prepared using PLGA7510, PLLGA7510, and their physical mixtures, it was suggested that the influence of Tg on drug release behavior was greater than that of crystallinity when the molecular weights were same and the Tg of the substances were sufficiently higher than the ambient temperature.

Effect of Glass Transition Temperature in Enhanced Polymeric Blend Membranes

The Enhanced Polymeric Blend Membranes (EPBM) have an exceptionally promising future in the gas separation industry due to improved physical and chemical properties compared to organic and inorganic membranes. In this research two reference membranes comprising PSU glassy and PVAc rubbery polymers were used as controls for comparative analysis. The research is focused on the preparation of flat sheet PSU/ PVAc polymeric blend membranes. The composition of PVAc contents varied between 5-20 wt% in the PSU matrix. Differential scanning calorimetry (DSC) analysis showed the existence of single glass transition temperature (Tg) for different membrane blends which indicated miscibility among the PSU/PVAc polymer blends. The glass transition temperature (Tg) miscibility among the polymeric blends were further judged by using Fox equation (series model) or Wood's equation (parallel model) or Pochan's equation (logarithmic model).

Effect of Glass Transition Temperature of Stabilizing Polymer of Air-Stable Gelatin-Stabilized Copper Fine Particles during Redox Two-Step Low-Temperature Sintering Process

Abstract It has been found in this study that the glass transition temperatures can be considered as the lowest temperature for sintering metal fine particles to obtain electro-conductive metallic layers from the differential scanning calorimetry measurement of the fine particles. Gelatin-stabilized copper fine particles could be sintered to form an electrically conductive copper layer with a resistivity of 1.9 × 10−5 Ω cm at as low as 150 °C using oxidation–reduction two-step sintering.

Effect of Glass Transition Temperature on the Energy Storage Properties of Nitroxide Radical Containing Polymers

Stable nitroxide radical bearing polymers are attracting much attention for their application as electrode materials in organic radical batteries. These unique redox-active polymeric materials have unusually rapid rates of electron-transfer for non-conjugated polymer systems. This behavior results in unique applications in batteries because of enhanced charging capability and excellent cycling stability of the nitroxide radical functionality. A greater understanding of the inherent charge transfer limitations in such systems, particularly with respect to the relationship between performance and structure of the radical bearing polymer, are paramount to further advancements in the field. While ion transport through neutral polymer networks has been well-studied for solid polymer electrolytes consisting of charged salts incorporated inside a neutral cross-linked polymer matrix, nitroxide radical materials differ dramatically in complexity from typical solid polymer electrolytes. It has been observed that ionic motion in the former systems is coupled with segmental motion of the polymer matrix; hence, ion transport can be correlated with a polymer’s glass transition temperature (T g). However, the T g of radical containing polymers is expected to change dramatically and reversibly upon charging and discharging between neutral and cationic states. Therefore, it is essential to evaluate how charge transfer is affected by changes in the energetics of molecular motion. In this work, we conducted a systematic study of a class of nitroxide radical polymers for which the T g of the materials are systematically tuned either by incorporating butyl acrylate comonomers into the backbone or by incorporating the nitroxide functionality at the terminus of a long alkyl chain. Preliminary synthesis, characterization, spectroscopic, and electrochemical data will be presented.

Effect of fiber surface modification on the lifetime of glass fiber reinforced polymerized cyclic butylene terephthalate composites in hygrothermal conditions

Abstract Mechanical performances of polymerized cyclic butylene terephthalate (pCBT) matrix, glass fiber reinforced pCBT (GF/pCBT), and nano-silica modified glass fiber/pCBT composites (nano-GF/pCBT) in hygrothermal condition were investigated. All the materials were aged in hygrothermal environments for up to three months, and then their mechanical strength degeneration ratio (SDR) was calculated. To study the aging effect of temperature, specimens with and without nano-silica modification were tested in temperatures ranging from 298 to 500 K. Differential scanning calorimeter (DSC) test, dynamic mechanical analysis (DMA), and fiber pull-out test were adopted to complement the experimental results. It is found that all the SDR-time curves follow the linear relationship in hygrothermal environment, while SDR-temperature curves follow a bilinear relationship due to the effect of glass transition temperature (Tg) of the matrix. Fibers modified by coating nano-silica on the surface could decrease SDR of the composites. This is due to the fact that the fillers on the fiber surface could resist the movement of pCBT molecular chain and diffusion of water molecules in aging conditions. The fiber pull-out test verifies that the interface strength between fiber and matrix is enhanced by the modification.

Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer

ABSTRACTEffect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer (COC)—including CO2 solubility, diffusivity, cell nucleation, and foam morphology—were investigated in this article. COCs of low Tg (78°C) and high Tg (158°C) were studied. Solubilities are 20–50% higher in high Tg COC than in the low Tg COC across the saturation temperature range. Diffusivities are about 15% higher on average in high Tg COC for temperatures up to 50°C. A much faster increase of diffusivity beyond 50°C is observed in low Tg COC due to it being in the rubbery state. Under similar gas concentration, high Tg COC starts foaming at a higher temperature. And the foam density decreases faster in low Tg COC with foaming temperature. Also, high Tg COC foams show about two orders of magnitude higher cell nucleation density than the low Tg COC foams. The effect of saturation temperature on microcellular foaming can be viewed as the effect of CO2 concentration. Nucleation density increases and cell size decreases exponentially with increasing CO2 concentration. Uniform ultramicrocellular structure with an average cell size of 380 nm was created in high‐Tg COC. A novel hierarchical structure composed of microcells (2.5 μm) and nanocells (cell size 80 nm) on the cell wall was discovered in the very low‐density high‐Tg COC foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42226.

Charge Carrier Mobility of Siliconized Liquid Triarylamine Organic Semiconductors by Time-of-Flight Spectroscopy.

Triarylamines are a well-established family of organic semiconductors. Recently, we have attached short silicone chains to these molecules to alter their mechanical properties. The resulting compounds are liquids at room temperature. We have undertaken to confirm the suitability of these molecules for use in thin film flexible devices. One fundamental property of semiconductors is the charge carrier mobility, which provides a quantitative estimate for how rapidly charge percolates through a material. The charge carrier mobility for a series of six recently developed liquid siliconized triarylamines was measured using time-of-flight spectroscopy (TOF). In order to evaluate the effect of glass transition temperature on mobility, TOF was performed for different electric fields at temperatures above and below the glass transition temperature. Mobilities were found to compare favorably to the charge carrier mobilities of conventional nonliquid triarylamines. It was further observed that the mobilities conform ...

The Effect of Glass Transition Temperature on the Procedure of Microwave–Freeze Drying of Mushrooms (Agaricus bisporus)

Freeze drying (FD) yields the best quality of dried mushroom but at the cost of a long drying time and high overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high-quality product, a microwave–freeze drying (MFD) technique was developed to dry mushrooms. The relationship between dried mushroom quality and the glass transition temperature during the MFD process was studied to optimize the MFD process. According to the change tendency of the glass transition temperature of mushroom during MFD, a step-down microwave loading scheme for the MFD process was developed to obtain good product quality.

Synthesis and characterization of thermally rearranged (TR) polymers: effect of glass transition temperature of aromatic poly(hydroxyimide) precursors on TR process and gas permeation properties

Soluble aromatic polyimides containing ortho-positioned hydroxy groups were synthesized as precursors for thermal rearrangement (TR) to polybenzoxazoles (PBOs). Fully imidized polyimides with high-molecular-weights were afforded via a ‘one-pot’ solution imidization technique (i.e., ester-acid method). The poly(hydroxyimide)s were designed to vary in their glass transition temperatures (Tg) by carefully selecting dianhydride–bisaminophenol combinations to introduce various levels of chain rigidity. TR conversion (imide-to-benzoxazole conversion) occurred in solid-state films only under inert atmosphere and over a temperature range of 300–450 °C, depending on the chemical structure (chain rigidity) of precursors. The effect of the precursor Tg on TR conversion was studied using TGA, DSC, FTIR and gel fraction measurements. The TR conversion temperature of imide-to-benzoxazole rearrangement strongly depended on the precursor Tg. Thus, for example, the feasible TR temperature was successfully reduced by ∼100 °C by lowering the precursor Tg by using a bisphenol A type dianhydride in the polymer synthesis. Gas permeation properties of representative TR systems are also reported. The TR process significantly increased gas permeabilities while maintaining good selectivities. By correlating the TR conversion degree with gas transport properties, there appears to be an optimal TR conversion degree that can maximize both gas permeability and selectivity. Systematic studies on TR polymers derived from low Tg precursors were suggested to further explore this correlation.

Correlation of glass-forming ability to thermal properties in Ti-based bulk metallic glasses

Ti45.8Zr6.2Cu45−xNixSn2Si1 (x=0, 2, 4, 5, 7, 9, 11, 13 and 15at.%) and Ti52−yZryCu40.9Ni5.1Sn2 (y=4, 6, 8, 10, 12, 14 and 16at.%) bulk metallic glasses with critical diameters up to 4mm were prepared by copper mold casting. The thermal properties and crystallization behavior of these Ti-based glassy alloys have been investigated in detail. It is shown that the higher the onset temperature of the last crystallization event (Tn), the larger the glass forming ability (GFA). By considering the comprehensive effect of glass transition temperature (Tg), the onset temperature of the first crystallization event (Tx), Tn and liquidus temperature (Tl), we proposed a parameter N=(2Tx−Tg+Tn)/2Tl for the evaluation of GFA. It is found that this criterion is particularly effective for the BMGs which show multistage crystallization events upon heating.