1- What are the differences between G’, G’’, and phase angle?
G’ is called the elastic modulus and it represents the energy that structured system will gain from the oscillatory motion as long as the motion is not disrupting the structure. It is also called the storage modulus as it describes the energy stored in the structure. If the interaction between the ingredients, are high then the value of G’ will also be high.
G” is called the viscous modulus also known as the loss modulus. This describes the part of energy that is lost as a result of the viscous dissipation. This type of modulus is only related to the number of friction which is creating interaction, the greater the number of temporary interactions the higher the value of G”.
Phase angle which is calculated as tan d (G”/G’) is associated with the degree of viscoelasticity of the sample being studied. If the value of tan d is high, then the degree of elasticity will also be higher hence the sample being of solid -ike in nature. The phase angle can be used to describe the properties of the sample.
If the value of phase angle is 900, then the sample is viscous
If the value of phase angle is 00, then the sample is elastic
If the value of phase angle is between 00 and 900, then the sample is viscoelastic
If the value of phase angle is greater than 450, then the sample is more liquid
If the value of phase angle is less than 450, then the sample is more solid
If the value of phase angle is 450, then the sample is equally liquid-solid
2- Explain what is shear thinning materials?
Shear thinning involves an effect whereby a fluid’s resistance to flow declines with an increasing rate of shear stress (Baeurle, Hotta and Gusev, 2006). The fluid’s resistance to flow is also known as the fluid’s viscosity. Materials that have shear thinning can be classified under the following two categories; either pseudoplastic or thixotropic and is commonly found in some complex solutions like the lava, blood, paint, nail polish and whipped cream. The property is also common to polymer solutions. Pseudoplasticity can be seen when a bottle of tomato sauce is squeezed and the contents are forced to undergo a change in viscosity. The force will make the contents to change from being thick and flow freely just like water. The Examples of shear thinning include tomato sauce and modern paints (Lewis and Price, 1972).
3- What is the effect of temperature sweep and frequency sweep on different materials?
The graph shown below shows the temperature sweep (Time Vs Voltage)
According to the graph, as the temperature increases, the output of the CE amplifier decreases.
The frequency sweep is the sine waveform that starts from 20Hz to 20KHz. The effect of burn in is solid.
4- In texture profile analysis, give two examples of the first one rubbery material and the second crunch material and the differences between them in two areas.
Examples of rubbery materials include:
Polybutadiene
Copolyester
These crunch processes can also be used to produce high solids food material: confections
The graph above shows how the transition occurs between the manufacturing of the rubbery materials and the glass materials. The graph also shows the relationship between the storage and the loss modulus.
References
1. PR Lewis and C Price, Polymer, 13, 22 (1972) Modern Plastic Mid-October Encyclopedia Issue, Introduction to TPEs, page:109-110
2. S.A. Baeurle, A. Hotta and A.A. Gusev, 'A new semi-phenomenological approach to predict the stress relaxation behavior of thermoplastic elastomers,' Polymer 46, 4344-4354 (2005)
3. S.A. Baeurle, T. Usami and A.A. Gusev, 'A new multiscale modeling approach for the prediction of mechanical properties of polymer-based nanomaterials,' Polymer 47, 8604-8617 (2006)
4. S.A. Baeurle, A. Hotta and A.A. Gusev, 'On the glassy state of multi-phase and pure polymer materials,' Polymer 47, 6243-6253 (2006)
