Finishing technolo
Finishing technology
II.2.1.Treatments applied
The fabrics used in heart prostheses undergo special treatments before being backyard, these treatments include compaction, thermal
II.2.1.1.Compaction
The woven structures and to greater extent the knitted structures are initially too permeable to liquids for direct application, a process of compaction under controlled conditions are therefore necessary to reduce the porosity of the fabrics to acceptable levels , this can be accomplished by either thermal or chemical treatments , which reverse the change effected during the heat-drawing of the complement continuous – filament yarns . The thermal process uses dry or liquid heat, and the chemical process make use of swelling agents or solvents or a combination of the two. Consequent changes in the molecular arrangement degree of orientation and crystallinity normally accompanied by significant decreases in tensile strength, for example the application of mixture of trichloroacetic acid and methylene chloride have been found to cause more than a 30% reduction in the tensile strength of yarns when treated for 15 min, further more it has been found that the physical changes in the fibers may affect the healing performance of the prosthesis. (100) Grafts are subjected to various procedures before they are backaged and get ready for use. Compaction process serves to improve durability and reduces the porosity nevertheless compaction is essential in grafts, and it is advisable to select chemicals that do not bring about very significant changes in the materials.
surface treatment (calendring), crimping, coating and sterilization
