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Linear and Non-Linear Rheological Properties of Foods
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Ozlem C. Duvarci, Gamze Yazar, Hulya Dogan, Jozef L. Kokini
Molecular weight, composition, crystallinity and chemical structure alter the glass transition temperature of materials significantly. Low molecular weight compounds, such as water, act as an effective plasticizer by lowering the Tg of biopolymers. Kalichevsky and Blanshard (1993) studied the effect of fructose and water on the glass transition of amylopectin and observed that the fructose has a more significant effect on Tg at low water contents. Gontard et al. (1993) reported on the strong plasticizing effect of water and glycerol on mechanical and barrier properties of edible wheat gluten films.
1 Properties of Electronic Packaging Materials
Published in Mitel G. Pecht, Rakesh Agarwal, Patrick McCluskey, Terrance Dishongh, Sirus Javadpour, Rahul Mahajan, Electronic Packaging: Materials and Their Properties, 2017
Mitel G. Pecht, Rakesh Agarwal, Patrick McCluskey, Terrance Dishongh, Sirus Javadpour, Rahul Mahajan
Glass transition temperature, Tg. The glass transition temperature is a material property of polymers that is generally not exhibited by metals or ceramics. The glass transition temperature is the temperature at which a material changes from a hard, brittle, “glass-like” form to a softer, rubberlike consistency. The change in state occurs over a range of temperature for amorphous polymers. Crystalline polymers such as polytetrafluroethelene (PTFE) exhibit a unique melting point rather than passing through stages of decreasing viscosity with increased temperature. Typical TgS for common resin materials are listed in Table 5. The test method for glass transition temperature is covered in ASTM E1363.
Materials for Optical Systems
Published in Anees Ahmad, Handbook of Optomechanical Engineering, 2017
Trent Newswander, Roger A. Paquin
Selection of adhesive materials involves engineering trades. The adhesive must be adequately strong and stiff to effectively act as the joining method. However, these same properties result in the stressing of the optical element, which can produce optical surface distortion and optical index variation in transmissive optical media. Initially, stress results from the adhesives cure shrinkage with compounding effects created from elevated temperature curing. Adhesives can have very high coefficients of thermal expansion, especially above its respective glass transition temperature. Glass transition is the transition of the material from an amorphous rigid state to a more flexible state, which produces substantial property changes in strength, stiffness, and rate of thermal expansion. This nonlinear temperature-dependent change in properties must be accounted for in the design, analysis, and use of adhesives.
Evaluation and modelling of low-temperature fracture properties of asphalt binders in thin film by means of the local fracture test
Published in Road Materials and Pavement Design, 2023
Chiara Tozzi, Ferhat Hammoum, Orazio Baglieri
The glass transition temperature (Tg) is the parameter conventionally selected to represent the temperature range over which the glass transition occurs. The glass transition is defined as ‘a reversible change from a viscous state to a hard and brittle glassy one, that amorphous materials experience as the temperature decreases’ (Wunderlich, 1993). Since all the thermo-dependent mechanical properties are affected by this transition, the Tg is an important aspect to consider in discussing low-temperature brittleness of asphalt binders. The transition for asphalt binders generally takes place over a wide range of temperatures, due to the contribution of the different components of the material (Bahia & Anderson, 1993; Kriz et al., 2008; Moynihan et al., 1974). The assessment of the Tg strongly depends on the experimental procedure used and no standard methods are currently available for asphalt binders (Santagata et al., 2022). Among the various techniques adopted by researchers, Dynamic Mechanical Analysis (DMA) and Modulated Differential Scanning Calorimetry (MDSC) were selected in this study to determine the Tg of the investigated materials. The values obtained using the two techniques were indicated as and , respectively.
Effect of polymers and micro fibres on the thermo-chemical and rheological properties of polymer modified binders
Published in Australian Journal of Civil Engineering, 2023
Muhammad Aakif Ishaq, Filippo Giustozzi
MDSC was used to analyse the glass transition temperature (Tg), the melting temperature (Tm), melting enthalpy, and the crystalline factor, as shown in Table 3. The glass transition temperature value is not unique for polymers because the glassy state is not an equilibrium phase; therefore, a range of Tg has been provided in this study. The glass transition is a predictor of material properties for non-crystalline and semi-crystalline polymeric materials. A ‘kink’ in the plot of DSC between temperature and reversing heating flow represents the glass transition. Tg was estimated using a half-height method, which is used to locate the centre of the ‘kink’ or the slope in the sloping area. It can be seen from Table 3 that the elastomers resulted in a lower Tg value (−89.56°C) compared to elastomers-fibres (−2.40–6.36°C), whereas the elastomer-fibre showed a lower Tg value than plastomers (3.4–5.6°C) and plastomers-fibres (0.16–1.80°C). Low Tg value brings more resistance to thermal changes and contributes towards superior properties at low temperatures for the asphalt binder. Several factors affect the glass transition temperature, including molecular weight, measuring technique, and heating or cooling rates.
The interfacial interaction between asphalt binder and mineral filler: a comprehensive review on mechanisms, evaluation methods and influence factors
Published in International Journal of Pavement Engineering, 2022
Fan Li, Yuyou Yang, Linbing Wang
The specific heat value changes in glass transition can be measured via differential scanning calorimetry (DSC), as shown in Figure 10. Lipatov (1988) illustrated the relationship between the specific heat value changes and asphalt adsorbed film thickness. The weight constant of volume fraction in interface film λ can be calculated by Equation (24) where and represent the specific heat value changes in glass transition for asphalt mastic and corresponding asphalt binder, respectively. Subsequently, the thickness of asphalt–filler interaction film can be obtained by Equation (25), in which R represents the mean-volume radius of filler particles and can be measured by laser particle analyser. Based on the calculation method, Tan and Guo (2014) measured the adsorbed film thickness between Pen90 asphalt and different fillers. The results showed that their interface phase was 0.02–5.28 nm. And the bigger asphalt adsorbed film thickness indicates the stronger interaction ability with the filler particle.