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Textile composite materials for small intestine replacement

Deichmann T., Michaelis I., Junge K., Tur M., Michaeli W., Gries T.

Autex Research Journal

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2009

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Vol. 9, no. 4

105--108

EN

Down to the present day there are no sufficient techniques for a small intestine replacement, mostly because of the high standards for such implants. An indication for the need of novel operation techniques is the small patient survival rate of just 80 % for isolated small intestine transplantation and 62 % for combined liver-small intestine transplantation. The five year survival rates of the patients are merely 42 %. In order to overcome these limitations the authors are developing a partly resorbable textile-foam-composite for small intestine replacement The novel implant consists of a non resorbable textile PVDF mesh which is foamed with a micro porous, resorbable, and drug loaded polymer. The resorbable polymer serves on the one hand as initial sealing, therefore no intestine substance and bacteria can leak out into surrounding tissue, on the other hand it needs to be micro porous in order to ensure cell ingrowth. For the macro porous textile mesh warp knitting technology is used. The warp knitted tubular structure remains inside the body as a long term implant and provides mechanical support to ingrowing cells. In order to evaluate biomechanical properties of the warp knitted tubular PVDF meshes to compare them to the mechanical characteristics of small intestine tissue, tensile tests were conducted. Results of tensile tests on warp knitted structures with three different loop densities of 8, 12, and 16 loops per cm were compared to tensile tests on native small intestine tissue probes. The recorded curves of small intestine and warp knitted structures showed similar characteristics. The two characteristic Young Modules as well as the curve progression of the warp knitted structure with 12 loops per cm showed good accordance to the values of the native small intestine. Morphological analysis of the textile structures by digital image processing showed adequate pore size and porosity of the textile mesh.

2

The rheokinetics of a fast-curing polyurethane

Polushkin E., Polushkina O., Malkin A. Y., Blaurock J., Kleba I., Michaeli W.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

85-90

EN

A viscosity build-up of various fast curing polyurethane compositions has been investigated under isothermal conditions. A diisocyanate (DI) and a polyol (PO) forming the polyurethane in course of the exothermic reaction were mixed with an original single-screw mixer in the mass ratios from 1:3 to 3:1. The rheokinetic measurements were carried out with a modified cone-plate rheometer in range of shear rates from 0.025 to 6.2 s-1 at temperatures from 22 to 114oC. It has found that the maximal rate of viscosity growth is observed for the polyurethanes with the ratio of DI:PO falling in the narrow range between 1:1 and 1.5:1. It is interesting that these curing systems have shown the Newtonian behaviour up to the viscosity value of 105 Pa*s at the shear range of 0.04 to 0.6 s-1. The obtained curves can be fitted with the equation 'eta'='eta'0*exp(k*t) on the initial stage of the viscosity rise only. For more precise fitting of the entire rheokinetic curve a modified exponential equation with the parameter k depending on the time t is proposed.

3

Hydrodynamic model of the srim-process and its verification

Polushkin E., Kuznetsov V., Polushkina O., Malkin A. Y., Kleba I., Blaurock J., Michaeli W.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

297-302

EN

A two-dimentional hydrodynamic model of a rheokinetic fluid during filling a thin and long mold packed with reinforcement materials are proposed. A core layer of the mold is a porous and rather thick spacer mat. The location of other denser and thinner reinforcement materials into the mold was symmetrical with respect to the spacer mat. During mold filling the fluid easily flows along the core spacer mat and simultaneously impregnates the peripheral reinforcement mats. The model allows to simulate the flow front propagation of the fluid and pressure rise inside the mold during filling. In order to verify the model an original glass mold has been designed and built. The experimental results for the flow front propagation of the fluid were compared with the model predictions and a good coincidence between them has been obtained. For correct comparison of the experimental pressure profiles with the calculated data, the pressure losses in the mold gate must be taken into consideration. These losses can essentially exceed the pressure level into the mold.