Mechanical characterisation of bio-compatible, electro-spun non-wovens

In the electrostatic spinning process, a strong electrostatic field is used in order to pull thin fibres from a polymer solution or polymer melt. The electrospinning process can be used to produce non-wovens made of biocompatible polymeric fibres. These porous structures have potential applications as scaffolds in tissue engineering, as porous coatings of implants, and as filter materials. Depending on their application, the non-wovens have to fulfil a range of demands including being biocompatible, exhibiting a defined structure, and possessing a sufficient mechanical strength. Three polymer-solvent systems were electro-spun (poly-(L-lactic acid) (PLLA) in dichloromethane, a poly(vinylalcohol-co-ethylene) co-polymer (PVA-co-PE) in an isopropanol water mixture, and poly(urethane) (PU) in dimethylformamide). The non-wovens were collected either on a flat counter-electrode or on a grounded spinning cylinder. By varying the process parameters (concentration of the spinning solution, electrostatic field, mode of collection and spinning rate of the cylinder), non-wovens with different characteristics could be obtained. The structure of the non-wovens was characterized by scanning electron microscopy. The diameter of the fibres in the non-wovens were typically in the order of magnitude of one µm. By varying the mode of collection, non-wovens with different degrees of orientation could be obtained. The tensile mechanical behaviour (e.g. stiffness, strength, mode of failure) of the non-wovens was characterised with an EnduraTec ELF 3200 mechanical testing system. Samples cut from one non-woven show reproducible mechanical characteristics. The degree of orientation of the non-woven and the orientation of a preferred fibre-direction wi th respect to the testing direction influences the results of the mechanical tests strongly.