Ultrasonic Detection Of Soft Material Gel Formation Process

Comparing with methodes such as light dispersion, electronic transmission, ultrasonic attenuation measurements don't damage the sample and operate simply. So online testing can be achieved. In this paper, the glutin gelation was reviewed. The gelation of gelatin and acrylamide was studied using ultrasonic attenuation measurements and rheometer. The main results were described as follows:1. Setting the soft matter of glutaraldehyde cross-linked gelatin's formation as model, ultrasonic attenuation methods are used to detect the gelation process of different concentrations of crosslinker and gelatin solution. Experiments indicate that the echo time has little various also the proportion of PVME and gelatin solution is different. This shows that different proportion of gelatin solution and the PVME has no significantly influence to the speed of sound in solution. The volume of glutaraldehyde has affected on gelation efficaciously, that is to say, glutaraldehyde can promote the molecule of gelatin link together, the more volume of glutaraldehyde, the sooner the gel will form. The bigger the concentration of gelatin is, the greater the attenuation coefficient and the sooner of gelation. The experiment shows that the change of attenuation coefficient of gelatin solution without PVME is very small. It attests that the gelatin gel is stable. Add PVME to solution, the attenuation coefficient of gel is gradually decreased with the increasing temperature, it can be speculated, the attenuation coefficient of PVME solution with increasing temperature the attenuation coefficient is decreased with increasing temperature. The curve of gelatin solution with PVME can be regarded as a superposition of gelatin solution and PVME solution. After the gel-formed of gelatin solution with PVME, changing their tempearture alternantly between 21℃and 38℃, the attenuation coefficient is reversibly changed at a certain range. This means the conformation and aggregation of PVME is correspondingly changing. And it has a good reversibility to the tempearture change. This is because the PVME solution takes an open coil conformation at low tempearture and a compact coil conformation at high temperature. The conformation of PVME is reversible as the tempearture changes. The use of rheometer to detect the changes of viscoelastic parameters in gel formation process as contrast. The results showed that: the greater the concentration of gelatin solution is, the faster the gel forms. The higher the temperature is, the slower the gel formation will be. Which is conform to the ultrasound attenuation results, so we verify the feasibility and correctness of ultrasonic attenuation measurement.2. We also discuss the applicability of ultrasonic attenuation measurements in the studies of the changes status of acrylamide gel soft materials formation with different concentration glutaraldehyde cross-linked, acrylamide and temperature as a system. Rheological method is the measurements of changes of viscoelastic parameters in gel formation process by rheometer detection as contrast. It was shown that: the bigger the acrylamide concentration is, the greater the ultrasonic attenuation coefficient and the sooner of gel formation; the acrylamide gel is formed faster in the higher of temperature; the Acrylamide gel is formed faster in the higher of crosslinker. Which is conform to the ultrasound attenuation detecting results.