What determines gel point?

The gel point is determined as the time at which the tan ∂ vs frequency plot becomes independent of the applied frequency. Figure 9. Plots of dynamic moduli (G′ and G′′) vs frequency at the gel point for the determination of the critical exponent, n, for the power law dependence of the dynamic moduli on frequency.

How is gelation time calculated?

The gelation time of a thermoset molding compound is usually measured with a gel plate. In gel time evaluation with a gel plate, a small amount of the molding compound powder is softened to a thick fluid on a precisely controlled hot plate (usually set at 170°C) and periodically probed to determine gelation.

What is gelling reaction?

Gelation (gel transition) is the formation of a gel from a system with polymers. At that point in the reaction, which is defined as gel point, the system loses fluidity and viscosity becomes very large. The onset of gelation, or gel point, is accompanied by a sudden increase in viscosity.

What is gelling ability?

Gelling capacity can be defined as the ability of a substance to spontaneously absorb liquids within an aqueous surrounding. More often than not, this term is associated with hydrocolloids. Once dispersed in water, these absorb water and molecules become individualized.

How is gel point measured?

The gel point can be determined from various rheological criteria including (1) the point where the storage modulus, G′, and the loss modulus, G″, of the dynamic mechanical analysis are equal or tan δ = 1 [64], (2) the maximum in the tan δ [65,66], (3) the crossing point between the tangent line of the elastic modulus …

How do you control the time of alginate?

The set time of alginate is inversely proportional to the temperature of the water, so the colder the water the longer it takes to set, and you gain lots of working time. If you are looking to speed up the set, make the water warmer.

How do you measure gelling?

Using texture analysis, gels can be assessed by measuring their mechanical resistance to stress. In a simple gel strength measurement, using, for example, a TA. XTplus Texture Analyser, a cylinder probe typically of 0.5 inch diameter, is lowered into the gel system at a fixed speed.

What is gel temperature?

The gel temperature is the temperature at which a water-starch mixture changes from a liquid slurry to a gelatin-like solid. This is the point at which the material begins to function as an adhesive.

How do you calculate the conversion at the gel point?

For high functionality and free-radical initiated systems, gelation will typically occur at lower conversions. The conversion at the gel point can be calculated using the following equation: Take the simple diepoxy-diamine system with equal stoichiometry, where in the above equation:

What does gelling mean in rheumatoid arthritis?

Related to gelling: Gelling agent. A popular term for stiffness after rest, a finding typical of rheumatic diseases (e.g., juvenile rheumatoid arthritis or Still’s disease), which is variably accompanied by polyarthritis and guarding of joints against activity.

Does gelation occur at higher or lower conversions?

For high functionality and free-radical initiated systems, gelation will typically occur at lower conversions. The conversion at the gel point can be calculated using the following equation:

What is the gel point of epoxyamine?

The gel point may be calculated if the chemistry is known (1,2). Gelation in condensation systems like epoxy-amine typically occurs between 50 and 80% conversion ( a = 0.5 – 0.8).