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Polimerowe kompozyty elektroprzewodzące jako materiały o potencjale sensorycznym

Frąckowiak S., Kozłowski M.

Polimery

2010

T. 55, nr 5

390-398

Sporządzono kompozyty z osnową z polietylenu małej gęstości, polipropylenu lub polistyrenu, z dodatkiem sadzy w ilości 3, 6 bądź 9% mas. Sadza spełnia w nich rolę elektroprzewodzącego napełniacza, który tworząc struktury perkolacyjne umożliwia wytworzenie materiału przewodzącego prąd elektryczny i zastosowanie go w projektowaniu czujników. Oceniono potencjał sensoryczny uzyskanych kompozytów na podstawie pomiaru zmian napięcia elektrycznego próbek wystawionych na wielokrotne działanie rozpuszczalnika (toluenu bądź ksylenu). Analizowano wpływ cyklicznego spęczniania materiału próbki na charakter rejestrowanego sygnału elektrycznego. Wyznaczono lepkość otrzymanych kompozytów w stanie stopionym oraz określono ich właściwości mechaniczne.

Studies on the modification of polymeric matrix by an electrically conductive filler to obtain electrically conductive composites for use as sensors are presented. Polymers possess a limited ability to conduct electricity and for this reason are often used as insulators (Fig.1). However, filling a polymer with an appropriate amount of conducting filler enables the production of an electrically conductive composite material. The occurrence of the "selective deformation" effect enables the production of a specific structure of the composite. This effect generates a series of changes in the properties in the material under the influence of chemical compounds. Moreover, the electrical conductivity is also changed which in consequence allows the composite to detect chemical substances which come in contact with it. Depending on the type of material used as composite matrix, it is possible to detect specific chemical compounds. The sensory potentials of the obtained composites were determined on the basis of the measured electric current changes taking place in a sample after being repeatedly exposed to a solvent (Fig. 3-9). The repeated analysis cycle consisted, among others of the immersion in the solvent and drying in air of the sample. The influence of multiple swelling of the sensor on the character of the obtained electrical signal was presented. The mechanical properties (Fig. 13-18) and melt rheology (Fig. 10-12) of the composites was also determined.

Hydromagnetic flow due to ramped motion of the boundary

Jha B. K., Jibril H. M.

International Journal of Applied Mechanics and Engineering

2010

Vol. 15, no 4

1101-1109

The unsteady flow of a viscous, incompressible and electrically conducting fluid subject to a uniform transverse magnetic field near a horizontal plate having ramped motion is considered. A unified closed form analytical solutions have been obtained for the velocity field and the skin-friction corresponding to the cases of a magnetic field fixed relative to the fluid or the moving boundary. Under the assumption of a negligible induced magnetic field, the governing momentum equation has been solved exactly by using the Laplace-transform technique. The flow formation near ramped motion of the plate has also been compared with the flow formation near a plate having constant motion (impulsive motion). It is observed that velocity of the fluid in the case of ramped motion of the plate is always less than that of the flow induced by impulsive motion of the plate.